Abstract
Background
Exposure to stressful experiences is often accompanied by suppressing pain perception, referred to as stress-induced analgesia. The neuropeptides orexins are essential in regulating the mechanism that responds to stressful and painful stimuli. Meanwhile, the ventral tegmental area (VTA), as a part of descending pain inhibitory system, responds to noxious stimuli. The present study aimed to investigate the role of intra-VTA administration of orexin receptor antagonists on stress-induced antinociceptive responses in the animal model of acute pain.
Method
Ninety-three adult Wistar rats weighing 230–250 g were unilaterally implanted by a cannulae above the VTA. Animals were pretreated with different doses (1, 3, 10, and 30 nM/0.3 μl) of SB334867 as the orexin-1 receptor antagonist and TCS OX2 29 as the orexin-2 receptor antagonist into the VTA, just 5 min before 6 min exposure to forced swim stress (FSS). Nociceptive threshold was measured using the tail-flick test as a model of acute pain.
Results
The results showed that exposure to FSS could significantly increase analgesic responses. Moreover, intra-VTA administration of SB334768 and TCS OX2 29 blocked the antinociceptive effect of FSS in the tail-flick test.
Conclusion
The findings suggest that OX1 and OX2 receptors in the VTA might modulate the antinociceptive behaviors induced by FSS in part.
from Wiley: European Journal of Pain: Table of Contents https://ift.tt/3wUNl50
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