Browsing by Subject "dopamine"

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  • Albert, Katrina; Voutilainen, Merja H.; Domanskyi, Andrii; Airavaara, Mikko (2017)
    Gene delivery using adeno-associated virus (AAV) vectors is a widely used method to transduce neurons in the brain, especially due to its safety, efficacy, and long-lasting expression. In addition, by varying AAV serotype, promotor, and titer, it is possible to affect the cell specificity of expression or the expression levels of the protein of interest. Dopamine neurons in the substantia nigra projecting to the striatum, comprising the nigrostriatal pathway, are involved in movement control and degenerate in Parkinson's disease. AAV-based gene targeting to the projection area of these neurons in the striatum has been studied extensively to induce the production of neurotrophic factors for disease-modifying therapies for Parkinson's disease. Much less emphasis has been put on AAV-based gene therapy targeting dopamine neurons in substantia nigra. We will review the literature related to targeting striatum and/or substantia nigra dopamine neurons using AAVs in order to express neuroprotective and neurorestorative molecules, as well as produce animal disease models of Parkinson's disease. We discuss difficulties in targeting substantia nigra dopamine neurons and their vulnerability to stress in general. Therefore, choosing a proper control for experimental work is not trivial. Since the axons along the nigrostriatal tract are the first to degenerate in Parkinson's disease, the location to deliver the therapy must be carefully considered. We also review studies using AAV--synuclein (-syn) to target substantia nigra dopamine neurons to produce an -syn overexpression disease model in rats. Though these studies are able to produce mild dopamine system degeneration in the striatum and substantia nigra and some behavioural effects, there are studies pointing to the toxicity of AAV-carrying green fluorescent protein (GFP), which is often used as a control. Therefore, we discuss the potential difficulties in overexpressing proteins in general in the substantia nigra.
  • Abdurakhmanova, Shamsiiat; Semenova, Svetlana; Piepponen, T. Petteri; Panula, Pertti (2019)
    Hypothalamic histaminergic neurons regulate a variety of homeostatic, metabolic and cognitive functions. Recent data have suggested a modulatory role of histamine and histamine receptors in shaping striatal activity and connected the histaminergic system to neuropsychiatric disorders. We characterized exploratory behavior and striatal neurotransmission in mice lacking the histamine producing enzyme histidine decarboxylase (Hdc). The mutant mice showed a distinct behavioral pattern during exploration of novel environment, specifically, increased frequency of rearing seated against the wall, jumping and head/body shakes. This behavioral phenotype was associated with decreased levels of striatal dopamine and serotonin and increased level of dopamine metabolite DOPAC. Gene expression levels of dynorphin and enkephalin, opioids released by medium spiny neurons of striatal direct and indirect pathways respectively, were lower in Hdc mutant mice than in control animals. A low dose of amphetamine led to similar behavioral and biochemical outcomes in both genotypes. Increased striatal dopamine turnover was observed in Hdc KO mice after treatment with dopamine precursor l-Dopa. Overall, our study suggests a role for striatal dopamine and opioid peptides in formation of distinct behavioral phenotype of Hdc KO mice.
  • Hyry, Saimi (Helsingin yliopisto, 2022)
    The aim of the study. Spontaneous eye blink rate (sEBR) is a behavioral index that has been linked to frontostriatal dopaminergic activity. Reduced or increased dopaminergic activity due to clinical conditions tends to be associated with lower or higher sEBR, respectively, and sEBR can be modulated by pharmacological agents that affect dopamine signaling. Consequently, sEBR could serve as an easily accessible method of assessing brain dopaminergic tone indirectly in humans. It might be preferable to more expensive and invasive techniques such as positron emission tomography. However, it remains unclear whether variations in dopaminergic genes predict sEBR. In this cross-sectional study, the relationship between sEBR and dopaminergic genotype was examined in two samples. Two genetic polymorphisms were focused on: the COMT Val158Met polymorphism and the A1 allele of the Taq1A polymorphism. It was hypothesized that the COMT Val158Met polymorphism is associated with higher sEBR, and that the A1 allele of the Taq1A polymorphism is associated with lower sEBR. As BMI and diet have been linked with altered striatal dopamine function, the possible association between BMI, diet, and sEBR was studied exploratively. Methods. Data from three cross-sectional studies was used in this study: The intervention study (n = 31) is an experimental study that examines the effect of acute phenylalanine/tyrosine depletion on cognitive measures. The GREADT study (n = 86) focuses on the effects of genotype and diet on dopamine tone. The BEDOB study (n = 69) investigates neurocognitive mechanisms in obesity and binge eating disorder. Similar methodologies were used in the GREADT and the BEDOB studies, which is why these datasets were combined for the analyses. Blink rates were measured using an infrared eye tracking system. The participants completed the Dietary Fat and free Sugar Questionnaire (DFS) to assess how much they consumed saturated fat and refined sugar. In the GREADT/BEDOB sample, the associations between the polymorphisms, BMI, DFS-score, and sEBR were examined with univariate analyses of variance. In the intervention study sample, a generalized linear mixed model was run to check whether sEBR changed in the intervention and whether the genotypes, BMI, or DFS-score affected sEBR. Results. No influence of the genotypes was found on sEBR in either of the samples. BMI had a significant effect on sEBR in the GREADT/BEDOB sample. The association was significant in the overweight/obese group but not in the normal weight group. DFS-score did not influence sEBR in either of the samples. Conclusions. The results of this study converge with those of authors suggesting caution in using sEBR as a proxy for central dopamine functioning of healthy humans. In future studies, particular attention should be paid to methodological considerations when studying sEBR.
  • Leikas, Juuso V.; Kohtala, Samuel; Theilmann, Wiebke; Jalkanen, Aaro J.; Forsberg, Markus M.; Rantamaki, Tomi (2017)
    Parkinson's disease (PD) is a progressive neurodegenerative movement disorder primarily affecting the nigrostriatal dopaminergic system. The link between heightened activity of glycogen synthase kinase 3 beta (GSK313) and neurodegenerative processes has encouraged investigation into the potential disease-modifying effects of novel GSK3 beta inhibitors in experimental models of PD. Therefore, the intriguing ability of several anesthetics to readily inhibit GSK3 beta within the cortex and hippocampus led us to investigate the effects of brief isoflurane anesthesia on striatal GSK3 beta signaling in nave rats and in a rat model of early-stage PD. Deep but brief (20-min) isoflurane anesthesia exposure increased the phosphorylation of GSK3 beta at the inhibitory Ser9 residue, and induced phosphorylation of AKT(Thr308) (protein kinase B; negative regulator of GSK3 beta) in the striatum of naive rats and rats with unilateral striatal 6-hydroxydopamine (6-OHDA) lesion. The 6-OHDA protocol produced gradual functional deficiency within the nigrostriatal pathway, reflected as a preference for using the limb ipsilateral to the lesioned striatum at 2 weeks post 6-OHDA. Interestingly, such motor impairment was not observed in animals exposed to four consecutive isoflurane treatments (20-min anesthesia every 48 h; treatments started 7 days after 6-OHDA delivery). However, isoflurane had no effect on striatal or nigral tyrosine hydroxylase (a marker of dopaminergic neurons) protein levels. This brief report provides promising results regarding the therapeutic potential and neurobiological mechanisms of anesthetics in experimental models of PD and guides development of novel disease-modifying therapies.
  • Laukkanen, Heidi (Helsingin yliopisto, 2022)
    The aim of the study. Working memory (WM) is a cognitive function that relies on the neurotransmitter dopamine. WM has multiple subfunctions: maintaining relevant information, ignoring distractors, and updating the information when needed. Information maintenance and ignoring irrelevant stimuli are associated with brain activity in the prefrontal cortex and updating information with the striatum. A connection between polymorphisms within the dopaminergic genes COMT (COMT Val158Met polymorphism) and DRD2/ANKK1 (Taq1A polymorphism), and WM performance has been established in previous studies, and these genes seem to impact dopamine signaling in the prefrontal cortex and striatum, respectively. The present study investigates associations between dopaminergic gene polymorphisms and WM performance. The main research questions include the main effects and interactions that the genes have to WM on performance overall and WM stability and flexibility in particular. The study investigates also whether obesity, diet, and age affect WM performance, as there are indications for these from previous studies. Methods. Data from three separate cross-sectional studies with a total of 244 participants was used. A computer-based visual working memory task was used to assess the WM performance measures accuracy and reaction time. Other measurements included blood measures, Body Mass Index (BMI), and the Dietary Fat and free Sugar Questionnaire (DFS). Results and conclusion. In WM accuracy analyses, there was a significant main effect for the task condition as well as interactions between the COMT*task condition and COMT*Taq1A*task condition. In the three-way interaction analysis for WM accuracy, the most beneficial combination was Met/Met & A1- in the task condition measuring the stability, and Val/Met & A1+ in the task condition measuring the flexibility. This result gives support for established knowledge about how Met/Met combined with A1- is beneficial especially for WM stability and maintenance. Also, the inverted-U shape theory and previous studies' results of A1+ being beneficial in executive functions updating tasks, give support to the result regarding WM flexibility. In the three-way interaction reaction time analysis, the combination of Val/Met & A1+ was the fastest in every task condition. However, the significant differences were mainly between A1- and A1+ genotypes when combined with Val/Met and between Met/Met and Val/Met genotypes when combined with A1-. The two-way interaction between COMT Val158Met and task condition did not remain significant in pairwise comparisons. In reaction time analyses, COMT Val158Met and Taq1A had a significant main effect where reaction times followed the order: Met/Met < Val/Val < Val/Met, with Val/Met being significantly slower than the others and in Taq1A A1+ < A1-, with a significant difference. Adding age, BMI, and DFS to the analyses did not affect the significant/non- significant main effects or interactions in the analyses. The results of this thesis converge with the previous knowledge about these genotypes having an interacting effect on working memory stability and flexibility. However, these effects are complex to interpret as the results and their directions differed between the task conditions and outcome measurements. In the main outcome variable (accuracy), the result regarding the WM stability is well in line with previous literature about the Met/Met & A1- combination being beneficial to WM performance, and the result about Val/Met & A1+ being beneficial for WM flexibility gets preliminary support from executive function studies, but also opens new research avenues regarding the WM flexibility subfunction.
  • Brodski, Claude; Blaess, Sandra; Partanen, Juha; Prakash, Nilima (2019)
    Dopamine-synthesizing neurons located in the mammalian ventral midbrain are at the center stage of biomedical research due to their involvement in severe human neuropsychiatric and neurodegenerative disorders, most prominently Parkinson's Disease (PD). The induction of midbrain dopaminergic (mDA) neurons depends on two important signaling centers of the mammalian embryo: the ventral midline or floor plate (FP) of the neural tube, and the isthmic organizer (IsO) at the mid-/hindbrain boundary (MHB). Cells located within and close to the FP secrete sonic hedgehog (SHH), and members of the wingless-type MMTV integration site family (WNT1/5A), as well as bone morphogenetic protein (BMP) family. The IsO cells secrete WNT1 and the fibroblast growth factor 8 (FGF8). Accordingly, the FGF8, SHH, WNT, and BMP signaling pathways play crucial roles during the development of the mDA neurons in the mammalian embryo. Moreover, these morphogens are essential for the generation of stem cell-derived mDA neurons, which are critical for the modeling, drug screening, and cell replacement therapy of PD. This review summarizes our current knowledge about the functions and crosstalk of these signaling pathways in mammalian mDA neuron development in vivo and their applications in stem cell-based paradigms for the efficient derivation of these neurons in vitro.
  • Montonen, Heidi (Helsingfors universitet, 2013)
    Literature review: The plasma membrane DA transporter (DAT) belongs to the family of Na+/ClÙÄÉ≠ dependent neurotransmitter transporters. DAT is the primary mechanism for clearance of dopamine from the extracellular space and transporting it back to the presynaptic nerve terminals. There's a great interest in the DAT and its regulation as its substrate, dopamine, mediates a wide array of physiological functions e.g. locomotor activity, cognition and the control of motivated behaviors. With selective transport DAT limits the intensity and the duration of dopaminergic signal. Its function is regulated by several kinases, phosphatase and protein-protein interactions. The altered expression of DAT may be related to several neurological diseases such as Parkinson's disease, addiction and ADHD. To study DAT's function, several genetically modified mouse lines including DAT knockout mice, DAT knockdown mice and DAT knock in mice with elevated DAT levels have been generated. Experimental part: Glial cell line-derived neurotrophic factor (GDNF) plays important role in the survival and function of dopaminergic neurons, learning, memory and synaptic plasticity. More recently, several studies have shown that GDNF can also negatively regulate the actions of abused drugs. The aim of this study was to investigate GDNF's role and mechanism of action in plasticity and function of the dopaminergic neurons projecting to striatum. For that purpose, we used in vivo microdialysis in freely moving mice. We chose two different mouse lines: MEN2B mice with constitutive active Ret-signaling and elevated striatal dopamine concentrations, and GDND-cKO mice that lack GDND in the central nervous system. Microdialysis guide cannula was implanted in the dorsal striatum in the stereotaxic surgery and the mice were allowed to recover for 5-7 days. The concentrations of dopamine and its metabolites DOPAC and HVA and also 5-HIAA were determined from the samples by highperformance liquid chromatography. Microdialysis was performed twice for every mouse on days 1 and 4. Between microdialysis days, the mice were given amphetamine 1 mg/kg i.p. on days 2 and 3. In the microdialysis experiment, the mice received amphetamine stimulation (100 µM/60 min) via microdialysis probe. The placements of microdialysis probes were verified from fixed brain sections after the experiments. Amphetamine increased the dopamine output in both mouse lines, but there were no statistically significant differences in striatal dopamine concentrations between genotypes neither after acute nor chronic administration. However, there was a difference between the dopamine outputs in days 1 and 4 in both MEN2B and GDNF-cKO mice: The striatal dopamine concentrations were significantly lower on the second microdialysis day. This may be a sing from tolerance to the drug. However, without more research, it is not possible, by this experiment, to draw direct conclusions of GDNF's role in addiction and in plasticity in striatum. It is possible that the differences between genotypes are too small to be seen with microdialysis. Development of compensatory mechanisms in mice cannot be ruled out either. Effects may also vary between different brain areas.
  • Leino, Sakari; Koski, Sini K.; Rannanpää, Saara; Salminen, Outi (2018)
    The treatment of Parkinson's disease is often complicated by levodopa-induced dyskinesia (LID), and antidyskinetic treatment options are currently sparse. Nicotinic acetylcholine receptors have been suggested as potential targets for treatment of LID, as nicotinic agonists have been reported to alleviate LID in animal models. We aimed at the first independent replication of an antidyskinetic effect by nicotine using a mouse model of LID, and at investigation of its mechanisms by studying the release of [H-3]dopamine from synaptosomes prepared from the dorsal and ventral striatum. Chronic nicotine treatment in drinking water inhibited the development of LID in mice lesioned unilaterally with 6-hydroxydopamine and treated chronically with levodopa and benserazide. The antidyskinetic nicotine treatment had no effect on [H-3]dopamine release mediated by alpha 4 beta 2* nicotinic receptors, but decreased alpha 6 beta 2*-mediated [H-3]dopamine release in the lesioned dorsal striatum and the ventral striatum. In addition, nicotine treatment restored [H-3]dopamine release in the lesioned ventral striatum to intact levels. The results support a role for nicotinic receptors as drug targets for treatment of LID, and suggest that striatal presynaptic alpha 6 beta 2* receptors are important mediators of nicotine's antidyskinetic effect.
  • Lei, Jing; Ye, Gang; Pertovaara, Antti; You, Hao-Jun (2020)
    Here we investigated variations of endogenous descending modulation of nociception and therapeutic effects of intramuscular (i.m.) heating-needle stimulation in early stage of Parkinson's disease (PD) induced by unilateral microinjection of 3.5 mu l of 2.5 mu g/mu l 6-hydroxydopamine into the rat striatum. Paw withdrawal reflexes to noxious mechanical and heat stimuli in PD rats with and without exposure to i.m. 5.8% saline induced muscle nociception were evaluated. Experimental PD had no influence on mechanical or heat sensitivity in the baseline condition, whereas descending facilitation was stronger and descending inhibition was weaker in PD rats than vehicle-treated or naive rats during muscle nociception (P <0.05). Striatal administration of 5 mu g of dopamine failed to reverse the PD-associated changes in descending facilitation or inhibition, whereas dopamine in the thalamic mediodorsal (MD) nucleus and ventromedial (VM) nucleus significantly decreased the increase in descending facilitation and reversed the attenuation in descending inhibition, respectively (P <0.05). I.m. 43 degrees C of heating-needle stimulation had no effects on the enhanced descending facilitation in PD rats, but it markedly increased descending inhibition and reversed the increase in the number of apomorphine-induced body rotations (P <0.05), which effects were dose-dependently attenuated by raclopride, a dopamine 2 receptor antagonist, in the thalamic VM nucleus (P <0.05). The results indicate that the early-stage PD is associated with enhanced descending facilitation and weakened descending inhibition. From clinical perspective, 43 degrees C heat therapeutic regime promises to selectively enhance descending inhibition that is accompanied by improvement of motor dysfunction in PD. (c) 2020 IBRO. Published by Elsevier Ltd. All rights reserved.
  • Jaatinen, Pia; Sarviharju, Maija; Raivio, Noora; Eriksson, Peter; Hervonen, Antti; Kiianmaa, Kalervo (2013)
  • Leopold, Anna V.; Shcherbakova, Daria; Verkhusha, Vladislav V. (2019)
    Understanding how neuronal activity patterns in the brain correlate with complex behavior is one of the primary goals of modern neuroscience. Chemical transmission is the major way of communication between neurons, however, traditional methods of detection of neurotransmitter and neuromodulator transients in mammalian brain lack spatiotemporal precision. Modern fluorescent biosensors for neurotransmitters and neuromodulators allow monitoring chemical transmission in vivo with millisecond precision and single cell resolution. Changes in the fluorescent biosensor brightness occur upon neurotransmitter binding and can be detected using fiber photometry, stationary microscopy and miniaturized head-mounted microscopes. Biosensors can be expressed in the animal brain using adeno-associated viral vectors, and their cell-specific expression can be achieved with Cre-recombinase expressing animals. Although initially fluorescent biosensors for chemical transmission were represented by glutamate biosensors, nowadays biosensors for GABA, acetylcholine, glycine, norepinephrine, and dopamine are available as well. In this review, we overview functioning principles of existing intensiometric and ratiometric biosensors and provide brief insight into the variety of neurotransmitter-binding proteins from bacteria, plants, and eukaryotes including G-protein coupled receptors, which may serve as neurotransmitter-binding scaffolds. We next describe a workflow for development of neurotransmitter and neuromodulator biosensors. We then discuss advanced setups for functional imaging of neurotransmitter transients in the brain of awake freely moving animals. We conclude by providing application examples of biosensors for the studies of complex behavior with the single-neuron precision.
  • Dobewall, Henrik; Saarinen, Aino; Lyytikäinen, Leo-Pekka; Keltikangas-Järvinen, Liisa; Lehtimäki, Terho; Hintsanen, Mirka (2021)
    Background: We define compassion as an enduring disposition that centers upon empathetic concern for another person's suffering and the motivation to act to alleviate it. The contribution of specific candidate genes to the development of dispositional compassion for others is currently unknown. We examine candidate genes in the oxytocin and dopamine signaling pathways. Methods: In a 32-year follow-up of the Young Finns Study (N = 2,130, 44.0% men), we examined with multiple indicators latent growth curve modeling the molecular genetic underpinnings of dispositional compassion for others across the life span. We selected five single nucleotide polymorphisms (SNPs) whose functions are known in humans: rs2268498 (OXTR), rs3796863 (CD38) (related to lower oxytocin levels), rs1800497 (ANKK1/DRD2), rs4680 (COMT), and rs1611115 (DBH) (related to higher dopamine levels). Compassion was measured with Cloninger's Temperament and Character Inventory on three repeated observations spanning 15 years (1997-2012). Differences between gender were tested. Results: We did not find an effect of the five SNPs in oxytocin and dopamine pathway genes on the initial levels of dispositional compassion for others. Individuals who carry one or two copies of the T-allele of DBH rs1611115, however, tend to increase faster in compassion over time than those homozygotes for the C-allele, b = 0.063 (SE = 0.027; p = 0.018). This effect was largely driven by male participants, 0.206 (SE = 0.046; p <0.001), and was not significant in female participants when analyzed separately. Conclusions: Men who are known to have, on average, lower compassion than women seem to reduce this difference over time if they carry the T-allele of DBH rs1611115. The direction of the association indicates that dopamine signaling activity rather than overall dopamine levels might drive the development of compassion.
  • Koski, Sini K.; Leino, Sakari; Panula, Pertti; Rannanpää, Saara; Salminen, Outi (2020)
    The brain histaminergic and dopaminergic systems closely interact, and some evidence also suggests significant involvement of histamine in Parkinson’s disease (PD), where dopaminergic neurons degenerate. To further investigate histamine-dopamine interactions, particularly in the context of PD, a genetic lack of histamine and a mouse model of PD and levodopa-induced dyskinesia were here combined. Dopaminergic lesions were induced in histidine decarboxylase knockout and wildtype mice by 6-hydroxydopamine injections into the medial forebrain bundle. Post-lesion motor dysfunction was studied by measuring drug-induced rotational behavior and dyskinesia. Striatal tissue from both lesioned and naïve animals was used to investigate dopaminergic, serotonergic and histaminergic biomarkers. Histamine deficiency increased amphetamine-induced rotation but did not affect levodopa-induced dyskinesia. qPCR measurements revealed increased striatal expression of D1 and D2 receptor, DARPP-32, and H3 receptor mRNA, and synaptosomal release experiments in naïve mice indicated increased dopamine release. A lack of histamine thus causes pre- and postsynaptic upregulation of striatal dopaminergic neurotransmission which may be reflected in post-lesion motor behavior. Disturbances or manipulations of the histaminergic system may thus have significant consequences for dopaminergic neurotransmission and motor behavior in both healthy and disease conditions. The findings also represent new evidence for the complex interplay between dopamine and histamine within the nigrostriatal pathway.
  • von Bagh, Anna (Helsingin yliopisto, 2022)
    Objectives. Motivational contexts exert a profound influence on behavior biasing actions in sometimes detrimental ways. In Pavlovian bias, reward-predicting conditioned cues elicit approach behavior while aversively associated cues elicit withdrawal, with capacity to impact instrumental goal-driven behavior. Similar bias has been suggested to be produced by instrumental learning. Motivational biases have been linked to dopaminergic system but the precise role of dopamine in their modulation is unclear. The present study investigated genetically driven variation in Pavlovian and instrumental learning biases by comparing task performance in subjects carrying different variants of two dopaminergic SNPs, COMT Val108/158Met and DRD2/ANKK1Taq1A. Associations with BMI, diet, age and gender were studied. All subjects were expected to show motivational bias while no direct hypotheses were made concerning genotypic or lifestyle-mediated effects due to exploratory nature of the study. Methods. 160 subjects completed a probabilistic Go/NoGo learning task in an experimental within-subject design. Generalized mixed-model logistic regressions were used to predict differences by genotype in Go responding with and without covariants. Differences by genotype in computationally modelled latent bias estimates were studied with linear regression. Results and Conclusions. Confirming expectations, an overall effect of motivational bias and a general bias towards active responding were found. Relative to Val/Met and A1+, carriers of COMT Val/Val and Taq1A A1- variants showed superior learning of correct Go responses, indicating enhanced instrumental bias. BMI was inversely associated with learning rate while diet, age and gender did not explain variance. Results partly contradict previous findings and highlight the mixed nature of research regarding associations between dopaminergic SNPs and motivational biases.
  • Renko, Juho-Matti (Helsingfors universitet, 2012)
    Review of the literature: The purpose of the review is to go through what is known about mechanisms of actions of different neurotrophic factors (GDNF, neurturin, CDNF and MANF) and how they are transported within the brain. Neurotrophic factors are endogenous and secreted proteins which have a pivotal role in the development and maintenance of neurons. They support the survival of neurons and they can help them to recover from different injuries. Due to these functions neurotrophic factors might be beneficial for the treatment of neurodegenerative disorders like Parkinson's disease. There are a great deal of studies that clearly show the neuroprotective and neurorestrorative function of GDNF and neurturin on dopaminergic neurons. They are also studied in clinical studies with Parkinson's patients but the results have been partly contradictory. The signalling route of GDNF and neurturin via RET tyrosinekinasereceptor is fairly well known but the other mechanisms of action of these factors needs to be studied further. CDNF and MANF constitute a novel, evolutionarily conserved family of neurotrophic factors. They are shown to have neuroprotective and neurorestrorative actions on dopaminergic neurons both in vitro and in vivo in a rodent model of Parkinson's disease. The mechanisms of action of CDNF and MANF are not quite clear at the moment. There are two different domains in their structure both of which are likely to carry different functions. The N-terminal domains of these proteins are close to saposins, lipid and membrane binding proteins, some of which are shown to have neurotrophic and anti-apoptotic effects. The C-terminal domain of MANF, in turn, is structurally close to the SAP-domain of Ku70-protein which binds Bax in the cytoplasm and thus inhibits apoptosis mediated by Bax. CDNF and MANF might protect neurons both via intracellular mechanisms and extracellularly acting like a secreted neurotrophic factor. CDNF and GDNF are transported retrogradially from striatum to substantia nigra. MANF, unlike the others, is transported from striatum to the frontal cortex. MANF and CDNF are shown to have better diffusion properties in the brain parenchyma than GDNF. Experimental part: We studied, by means of microdialysis, the effects of CDNF, MANF and GDNF on the dopaminergic neurotransmission of naive rats within the striatum. Neurotrophic factors (10 µg) and PBS as a negative control were injected into the left striatum in stereotaxic surgery. After this rats recovered one week before the first mircodialysis. The second mircodialysis was performed three weeks after the surgery. The samples were collected from the left striatum of freely moving rats. During the microdialysis neurotransmission was stimulated by replacing the perfusion solution with hypertonic potassium solution and with amphetamine solution. The concentration of dopamine, DOPAC, HVA and 5-HIAA was measured from the dialysate samples. In vivo TH-activity experiment was carried out for three rats in each group. NSD1015 was injected i.p.after which rats were decapitated and their striatums were dissected. The concentration of L-DOPA, dopamine and metabolites on the treated and untreated hemisphere were analyzed from the tissue samples. The amount of L-DOPA in the striatum after NSD1015-treatment indicates how active TH-enzyme is. There were no significant differences in the concentrations of dopamine and metabolites during the baseline. MANF and CDNF increased the release of dopamine from the nerve terminals compared to GDNF and PBS one week after the surgery. Three weeks after the surgery there was still significant increase in the release of dopamine in MANF group compared to GDNF group. Also the dopamine-DOPAC-turnover was increased significantly in MANF group compared to GDNF and PBS groups one week after the surgery. DOPAC/HVA -ratio was significantly smaller in GDNF group than in other groups one week after the surgery. These findings suggest that MANF potentiates dopaminergic neurotransmission most drasticly. The effects of MANF seem to last longer time than the effects of other neurotrophic factors. CDNF seems to increase the release of dopamine from the nerve terminals as well. The potentiation of dopaminergic neurotransmission could be due to increased biosynthesis of dopamine or due to the potentiation of the function of nerve terminals. In the results of the TH-activity experiment there was a trend according to which L-DOPA is synthesized less after the neurotrophic factor treatment that after the PBS treatment. This suggests that neurotrophic factors might decrease the activity of TH-enzyme.
  • Varaschin, Rafael Koerich; Osterstock, Guillaume; Ducrot, Charles; Leino, Sakari; Bourque, Marie-Josee; Prado, Marco A. M.; Prado, Vania Ferreira; Salminen, Outi; Rannanpää (Nee Nuutinen), Saara; Trudeau, Louis-Eric (2018)
    Histamine H-3 receptors are widely distributed Gi-coupled receptors whose activation reduces neuronal activity and inhibits release of numerous neurotransmitters. Although these receptors are abundantly expressed in the striatum, their modulatory role on activity-dependent dopamine release is not well understood. Here, we observed that histamine H-3 receptor activation indirectly diminishes dopamine overflow in the ventral striatum by reducing cholinergic interneuron activity. Acute brain slices from C57BL/6 or channelrhodopsin-2-transfected DAT-cre mice were obtained, and dopamine transients evoked either electrically or optogenetically were measured by fast-scan cyclic voltammetry. The H-3 agonist alpha-methylhistamine significantly reduced electrically-evoked dopamine overflow, an effect blocked by the nicotinic acetylcholine receptor antagonist dihydro-beta-erythroidine, suggesting involvement of cholinergic interneurons. None of the drug treatments targeting H-3 receptors affected optogenetically evoked dopamine overflow, indicating that direct H-3-modulation of dopaminergic axons is unlikely. Next, we used qPCR and confirmed the expression of histamine H-3 receptor mRNA in cholinergic interneurons, both in ventral and dorsal striatum. Activation of H-3 receptors by alpha-methylhistamine reduced spontaneous firing of cholinergic interneurons in the ventral, but not in the dorsal striatum. Resting membrane potential and number of spontaneous action potentials in ventral-striatal cholinergic interneurons were significantly reduced by alpha-methylhistamine. Acetylcholine release from isolated striatal synaptosomes, however, was not altered by alpha-methylhistamine. Together, these results indicate that histamine H-3 receptors are important modulators of dopamine release, specifically in the ventral striatum, and that they do so by decreasing the firing rate of cholinergic neurons and, consequently, reducing cholinergic tone on dopaminergic axons. (C) 2018 IBRO. Published by Elsevier Ltd. All rights reserved.
  • Kuusimäki, Tomi; Al-Abdulrasul, Haidar; Kurki, Samu; Hietala, Jarmo; Hartikainen, Sirpa; Koponen, Marjaana; Tolppanen, Anna-Maija; Kaasinen, Valtteri (2021)
    Background PD comorbid with schizophrenia has been considered rare because these diseases associate with opposite alterations in the brain dopamine system. The objective of this study was to investigate the risk of PD after a diagnosis of a schizophrenia spectrum disorder. Methods Regionally, this was a retrospective record-based case-control study. The cohort included 3045 PD patients treated 2004-2019 in southwestern Finland. Nationally this was a nested case-control study using registers to examine Finnish patients who received a clinically confirmed PD diagnosis 1996-2015 (n = 22,189). PD patients with previously diagnosed schizophrenia spectrum disorder (separate analysis for schizophrenia) were included. Comparable non-PD control groups were derived from both data sets. All PD diagnoses were based on individual clinical examinations by certified neurologists. Results In PD patients, the prevalence of earlier schizophrenia spectrum disorder was 0.76% in regional data and 1.50% in nationwide data. In age-matched controls, the prevalence in the regional and national data was 0.16% and 1.31%, respectively. The odds ratio for PD after schizophrenia spectrum disorder diagnosis was 4.63 (95% CI, 1.76-12.19; P <0.01) in the regional data and 1.17 (95% CI, 1.04-1.31; P <0.01) in the national data. Conclusions Schizophrenia spectrum disorder increases the risk of PD later in life. This association was observed in both individual patient data and nationwide register data. Therefore, despite the opposite dopaminergic disease mechanisms, schizophrenia spectrum disorder increases rather than decreases the risk of PD. The increased PD risk could be related to risk-altering effects of dopamine receptor antagonists or to the increased vulnerability of the dopamine system induced by illness phase-dependent dopamine dysregulation in schizophrenia/schizophrenia spectrum disorder. (c) 2021 International Parkinson and Movement Disorder Society
  • Kinnunen, Marja (Helsingfors universitet, 2015)
    Histamine is a monoamine structured signal molecule, which takes part in many functions of living organisms. It was first found in brain approximately 70 years ago. Neuronal histamine regulates for example biological rhythms, energy metabolism and thermoregulation. In the 1980's, H3-receptor was recognized in the brain. Neuronal histamine regulates functions of other transmitters for example gamma-aminobutyric acid, glutamate, acetylcholine, noradrenaline and dopamine. Currently, the interactions of histamine and dopamine are not well characterized. Though, it is known that histaminergic fibers innerviate almost every dopaminergic area of the brain. There are also several H3-receptors in the striatum and in the limbic system. These brain areas are important for the rewarding effect of dopamine. The aim of the experimental part of this Master's thesis was to examine the location of histaminergic and dopaminergic nervous systems in mouse brain by using immunohistochemistry. Primary antibodies that were produced in rabbit (anti-histamine (HA)) and in mouse (anti-tyrosine hydroxylase (TH)), and secondary anti-rabbit and anti-mouse anti-bodies, that were produced in goat and conjugated with fluorophores, were used in the study. The samples were imaged with a confocal microscope. The primary aim was to find out, in which addiction related brain areas, histamine and dopamine cells and fibers are located and how they are situated in relation to each other. H3-receptor antagonists have been shown to decrease the consumption and rewarding effect of alcohol in animal models. Therefore, it was examined if non-imidazole structured H3-receptor antagonist also inhibits the rewarding effect of amphetamine, and if it decreases the locomotor activity induced by amphetamine. JNJ-39220675, a neutral antagonist of H3-receptor, and behavioral paradigm of conditioned place preference (CPP) were used in the experiment. CPP was also used to find out if D2-receptor agonist quinpirole cause reward or aversion. The effect of JNJ-39220675 on quinpirole's place preference and change in locomotor activity was also investigated. The interactions of these two pharmacological ligands were also examined in a separate locomotor activity experiment. C57BL/6J mice were used in all experiments. The results show that there are possible synaptic connections of histaminergic and dopaminergic system in substantia nigra, supramammillary nucleus, dorsomedial hypothalamic area and ventral periaqueductal grey area. Also, histaminergic nerve fibers innerviate to the dorsal striatum, which regulates motor functions, and to the ventral striatum, which is a part of the rewarding system of the brain. Hence, it is possible that histamine regulates the actions of dopa-mine in these brain areas. The behavioral experiments showed that JNJ-39220675 inhibits acutely increased locomotor activity caused by amphetamine, and decreases desensitation of decreased locomotor action caused by repeated dose of quinpirole. However, JNJ-39220675 did not have any effect on the rewarding effect of amphetamine, which causes strong sensitization. Also, JNJ-39220675 did not have an effect on quinpirole's aversive action. It remains to be seen, if H3-receptor is a potential target for new medicines in the treatment of different brain diseases and addiction in the future.
  • Huynh, Thi Le Hang (Helsingfors universitet, 2010)
    In the written part of my master -thesis I discuss about GDNF signalling and more specifically how the changes in the GDNF/GFRα1/Ret signaling affect the nigrostriatal dopaminergic neurons in different mutant mice. In the animal models of Parkinson's disease the neuroprotective and neurorestorative effects of exogenous GDNF are very clear which raises hope for use of GDNF in treatment of Parkinson's disease. In intact animals GDNF stimulates the function of nigrostriatal dopaminergic system. Revealing the role of GDNF/GFRα1/Ret signaling in development, maintenance and protection of nigrostriatal dopaminergic system will certainly help in search for treatment of neurodegeneration in Parkinson's disease. In knockout mouse models GDNF/GFRα1/Ret signaling is not crucial for prenatal nigrostriatal dopaminergic neuron development, but it has been shown that it plays an important role in the early postnatal development. Also, it was shown that reduced GDNF/GFRα1/Ret signaling compromises nigrotriatal dopaminergic system in heterozygous GDNF/GFRα1/Ret knockout mice. However the physiological roles of endogenous GDNF and its signalling in the nigrostriatal dopaminergic neurons are not very well understood. In the experimental part of my master -thesis I studied how reduced endogenous GDNF signaling affects the dopaminergic system after 6-OHDA induced neurotoxicity in the conventional heterozygous GDNF mice. Besides that I examined the effects of elevated endogenous GDNF on dopaminergic system of 7 days old so-called GDNF hypermorphs mice. The effects of reduced endogenous GFRα1 levels on dopaminergic system of 20 days old GFRα1 hypomorphs have also been studied. The obtained date showed that mice with the reduced levels of endogenous GDNF are not more susceptible to the 6-OHDA induced neurotoxicity than the wild type littermates. Elevated endogenous GDNF levels did not affect early postnatal development of the nigrostriatal dopaminergic system in GDNF hypermorphs mice as revealed by normal intensity of TH staining in striatum and normal number of TH-positive cells in the substantia nigra pars compacta. Reduced levels of endogenous GFRα1 levels did not affect monoamine levels in the striatum of GFRα1 hypomorph mice.
  • Pakarinen, Emmi; Danilova, Tatiana; Voikar, Vootele; Chmielarz, Piotr; Piepponen, Petteri; Airavaara, Mikko; Saarma, Mart; Lindahl, Maria (2020)
    Mesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum (ER) localized protein that regulates ER homeostasis and unfolded protein response (UPR). The biology of endogenous MANF in the mammalian brain is unknown and therefore we studied the brain phenotype of MANF-deficient female and male mice at different ages focusing on the midbrain dopamine system and cortical neurons. We show that a lack of MANF from the brain led to the chronic activation of UPR by upregulation of the endoribonuclease activity of the inositol-requiring enzyme 1 alpha (IRE1 alpha) pathway. Furthermore, in the aged MANF-deficient mouse brain in addition the protein kinase-like ER kinase (PERK) and activating transcription factor 6 (ATF6) branches of the UPR pathways were activated. Neuronal loss in neurodegenerative diseases has been associated with chronic ER stress. In our mouse model, increased UPR activation did not lead to neuronal cell loss in the substantia nigra (SN), decrease of striatal dopamine or behavioral changes of MANF-deficient mice. However, cortical neurons lacking MANF were more vulnerable to chemical induction of additional ER stress in vitro. We conclude that embryonic neuronal deletion of MANF does not cause the loss of midbrain dopamine neurons in mice. However, endogenous MANF is needed for maintenance of neuronal ER homeostasis both in vivo and in vitro.