Browsing by Subject "thalamic 'nociceptive discriminator'"
Now showing items 1-2 of 2
-
(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.
-
(2020)Here we investigated effects of intramuscular (i.m.) heating-needle stimulation on persistent muscle nociception evoked by i.m. injection of different doses (50-200 mu l) of complete Freund's adjuvant (CFA) in rats. Paw withdrawal reflexes evoked by noxious mechanical and heat stimulation as well as hind limb swelling were determined prior to and two weeks after the CFA injection. The unilateral injection of CFA induced a dose-related and long-lasting (5-14 d), bilateral secondary mechanical hyperalgesia and heat hypoalgesia associated with long-term limb swelling. A period of 30-45 min 43 degrees C heating-needle stimulation significantly enhanced the i.m. CFA-induced bilateral heat hypoalgesia and alleviated hind limb swelling. In contrast, 30-45 min 46 degrees C heatingneedle stimulation markedly enhanced both mechanical hyperalgesia and heat hypoalgesia, but failed to influence the CFA-induced hind limb swelling. Microinjection of P2X3 receptor antagonist A-317491 (0.5-4.5 nmol/0.5 mu l) into the thalamic ventromedial (VM) nucleus dose-dependently inhibited the 43 degrees C and 46 degrees C heating-needle stimulation-induced heat hypoalgesia, whereas the 46 degrees C heating-needle stimulation-induced mechanical hyperalgesia was significantly prevented by microinjection of A-317491 into the thalamic mediodorsal (MD) nucleus. In contrast, the hind limb swelling was not affected by the microinjection of A-317491 into the thalamic VM or MD nucleus. The present study indicates that in the CFA-induced persistent muscle nociception condition, 43 degrees C heating-needle stimulation selectively increases descending inhibition, which effect is modulated by the thalamic VM nucleus. In addition to the antinociceptive role of P2X3 receptors in the thalamic VM nucleus, P2X3 receptors within the thalamic MD nucleus participate in the descending facilitation evoked by i.m. 46 degrees C heating-needle stimulation. (C) 2020 IBRO. Published by Elsevier Ltd. All rights reserved.
