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  • Kohtala, Henrik Samuel; Theilmann, Wiebke; Rosenholm, Marko; Penna, Leena; Karabulut, Gulsum; Uusitalo, Salla; Järventausta, Kaija; Yli-Hankala, Arvi; Yalcin, Ipek; Matsui, Nobuaki; Wigren, Henna-Kaisa; Rantamäki, Tomi (2019)
    Rapid antidepressant effects of ketamine become most evident when its psychotomimetic effects subside, but the neurobiological basis of this lag remains unclear. Laughing gas (N2O), another NMDA-R (N-methyl-d-aspartate receptor) blocker, has been reported to bring antidepressant effects rapidly upon drug discontinuation. We took advantage of the exceptional pharmacokinetic properties of N2O to investigate EEG (electroencephalogram) alterations and molecular determinants of antidepressant actions during and immediately after NMDA-R blockade. Effects of the drugs on brain activity were investigated in C57BL/6 mice using quantitative EEG recordings. Western blot and qPCR were used for molecular analyses. Learned helplessness (LH) was used to assess antidepressant-like behavior. Immediate-early genes (e.g., bdnf) and phosphorylation of mitogen-activated protein kinasemarkers of neuronal excitabilitywere upregulated during N2O exposure. Notably, phosphorylation of BDNF receptor TrkB and GSK3 (glycogen synthase kinase 3) became regulated only gradually upon N2O discontinuation, during a brain state dominated by slow EEG activity. Subanesthetic ketamine and flurothyl-induced convulsions (reminiscent of electroconvulsive therapy) also evoked slow oscillations when their acute pharmacological effects subsided. The correlation between ongoing slow EEG oscillations and TrkB-GSK3 signaling was further strengthened utilizing medetomidine, a hypnotic-sedative agent that facilitates slow oscillations directly through the activation of (2)-adrenergic autoreceptors. Medetomidine did not, however, facilitate markers of neuronal excitability or produce antidepressant-like behavioral changes in LH. Our results support a hypothesis that transient cortical excitability and the subsequent regulation of TrkB and GSK3 signaling during homeostatic emergence of slow oscillations are critical components for rapid antidepressant responses.
  • Theilmann, Wiebke; Alitalo, Okko August; Yorke, Iris; Rantamäki, Tomi Pentti Johannes (2019)
    Objectives: Deep burst-suppressing isoflurane anesthesia regulates signaling pathways connected with antidepressant responses in the rodent brain: activation of TrkB neurotrophin receptor and inhibition of GSK3 beta kinase (glycogen synthase kinase 3 beta). The main objective of this study was to investigate whether EEG (electroencephalogram) burst suppression correlates with these intriguing molecular alterations induced by isoflurane. Methods: Adult male mice pre-implanted with EEG recording electrodes were subjected to varying concentrations of isoflurane (1.0-2.0% ad 20 min) after which medial prefrontal cortex samples were collected for molecular analyses, and the data retrospectively correlated to EEG ( + /- burst suppression). Results: Isoflurane dose-dependently increased phosphorylation of TrkB(Y816), CREBS133 (cAMP response element binding protein), GSK3 beta(S9) and p70S6k(T412/S424). The time spent in burst suppression mode varied considerably between individual animals. Notably, a subset of animals subjected to 1.0-1.5% isoflurane showed no burst suppression. While p-GSK3 beta(S9), p-CREBS133 and p-p70S6k(T412/S424) levels were increased in the samples obtained also from these animals, p-TrkB(Y816) levels remained unaltered. Conclusions: Isoflurane dose-dependently regulates TrkB and GSK3 beta signaling and dosing associated with therapeutic outcomes in depressed patients produces most prominent effects.
  • Antila, Hanna; Ryazantseva, Maria; Popova, Dina; Sipilä, Pia; Guirado, Ramon; Kohtala, Samuel; Yalcin, Ipek; Lindholm, Jesse; Vesa, Liisa; Sato, Vinicius; Cordeira, Joshua; Autio, Henri; Kislin, Mikhail; Rios, Maribel; Joca, Samia; Casarotto, Plinio; Khiroug, Leonard; Lauri, Sari; Taira, Tomi; Castren, Eero; Rantamäki, Tomi (2017)
    A brief burst-suppressing isoflurane anesthesia has been shown to rapidly alleviate symptoms of depression in a subset of patients, but the neurobiological basis of these observations remains obscure. We show that a single isoflurane anesthesia produces antidepressant-like behavioural effects in the learned helplessness paradigm and regulates molecular events implicated in the mechanism of action of rapid-acting antidepressant ketamine: activation of brain-derived neurotrophic factor (BDNF) receptor TrkB, facilitation of mammalian target of rapamycin (mTOR) signaling pathway and inhibition of glycogen synthase kinase 3 beta (GSK3 beta). Moreover, isoflurane affected neuronal plasticity by facilitating long-term potentiation in the hippocampus. We also found that isoflurane increased activity of the parvalbumin interneurons, and facilitated GABAergic transmission in wild type mice but not in transgenic mice with reduced TrkB expression in parvalbumin interneurons. Our findings strengthen the role of TrkB signaling in the antidepressant responses and encourage further evaluation of isoflurane as a rapid-acting antidepressant devoid of the psychotomimetic effects and abuse potential of ketamine.
  • Ning, Zhenfei; Williams, John M.; Kumari, Romika; Baranov, Pavel; Moore, Tom (2019)
    Autism is a genetically complex neurobehavioral disorder with a population prevalence of more than 1%. Cerebella abnormalities, including Purkinje cell deficits in the vermis, are consistently reported, and rodent models of cerebellar dysfunction exhibit features analogous to human autism. We previously analyzed the regulation and expression of the pseudoautosomal region 2 gene SPRY3, which is adjacent to X chromosome-linked TMLHE, a known autism susceptibility gene. SPRY3 is a regulator of branching morphogenesis and is strongly expressed in Purkinje cells. We previously showed that mouse Spry3 is not expressed in cerebella vermis lobules VI-VD and X, regions which exhibit significant Purkinje cell loss or abnormalities in autism. However, these lobules have relatively high expression of p75NTR, which encodes a neurotrophin receptor implicated in autism. We propose a mechanism whereby inappropriate SPRY3 expression in these lobules could interact with TrkB and p75NTR signaling pathways resulting in Purkinje cell pathology. We report preliminary characterization of X and Y chromosome-linked regulatory sequences upstream of SPRY3, which are polymorphic in the general population. We suggest that an OREG-annotated region on chromosome Yq12 similar to 60 kb from SPRY3 acts as a silencer of Y-linked SPRY3 expression. Deletion of a beta-satellite repeat, or alterations in chromatin structure in this region due to trans-acting factors, could affect the proposed silencing function, leading to reactivation and inappropriate expression of Y-linked SPRY3. This proposed male-specific mechanism could contribute to the male bias in autism prevalence.