Moradi M, Yazdian M R, Haghparast A. Lateral hypothalamus chemical stimulation-induced antinociception was attenuated by injection of dopamine D1 and D2 receptor antagonists in the ventral tegmental area . Physiol Pharmacol 2014; 18 (1) :36-46
URL:
http://ppj.phypha.ir/article-1-984-en.html
Abstract: (9699 Views)
Introduction: Stimulation or inactivation of the lateral hypothalamus (LH) produces antinociception. Studies
showed a role for the ventral tegmental area (VTA) in the antinociception induced by LH chemical stimulation through
the orexinergic receptors. In this study, we assessed the role of intra-VTA dopamine D1 and D2 receptors in
antinociceptive effects of cholinergic agonist, carbachol, microinjected into the LH in the tail-flick test.
Methods: Rats were unilaterally implanted with two separate cannulae into the VTA and LH. Intra-VTA infusions
of selective D1 receptor antagonist SCH-23390 (0.125, 0.25, 1 and 4 μg/0.3 μl saline) and selective D2 receptor
antagonist sulpiride (0.125, 0.25, 1 and 4 μg/0.3 μl DMSO) 2 min before microinjection of carbachol (125 nmol/rat
effective dose) into the LH was done. The antinociceptive effects of different doses of these antagonists were measured
using a tail-flick analgesiometer, and represented as maximal possible effect (%MPE) at 5, 15, 30, 45 and 60 min after
administration.
Results: The results showed that intra-VTA administration of D1 and D2 dopamine receptors antagonists could
significantly prevent the development of LH stimulation-induced antinociception. Administration of maximum doses of
SCH-23390 and Sulpiride (4 μg) didn’t affect the nociceptive behaviors in acute model of pain.
Conclusion: Thus dopamine receptors in the VTA play a modulating role in carbachol-induced analgesia within the
LH, in acute model of pain. It is supposed that there is an interaction between VTA dopaminergic and orexinergic
systems in pain modulation.