title: Role of dopamine D2-like receptors within the ventral tegmental area and nucleus accumbens in antinociception induced by lateral hypothalamus stimulation.
abstract: Several lines of evidence have shown that stimulation of the lateral hypothalamus (LH) can induce antinociception. It has been indicated that hypothalamic orexinergic neurons send projections throughout the dopamine mesolimbic pathway. Functional interaction between the LH and the main area of the mesolimbic pathway such as the ventral tegmental area (VTA) and the nucleus accumbens (NAc) implicates in pain modulation. Thus, in this study, we investigated the role of D2-like dopamine receptors within the VTA and NAc in the LH stimulation-induced antinociception. Male Wistar rats weighing 230-280 g were unilaterally implanted with two separate cannulae into the LH and VTA or NAc. Animals received intra-VTA (0.25, 1 and 4 μg/0.3 μl DMSO) and intra-accumbal (0.125, 0.25, 1 and 4 μg/0.5 μl DMSO) infusions of sulpiride as a selective D2-like receptor antagonist, prior to intra-LH carbachol (125 nM/rat) administration. In the tail-flick test, the antinociceptive effects were measured using a tail-flick algesiometer and represented as maximal possible effect (%MPE) within 5, 15, 30, 45 and 60 min after injections. Our results showed that intra-VTA and intra-accumbal sulpiride dose-dependently attenuated the LH stimulation-induced antinociception. However, the blockade of D2-like receptors within the NAc was more significant than that of the VTA. These findings show that D2-like dopamine receptors in these regions play an important role in the LH-mediated modulation of nociceptive information in the acute model of pain in the rats. It seems that this pain modulating system is more relevant to D2-like receptors in the nucleus accumbens.
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, P.O. Box 19615-1178, Tehran, Iran.
authors.forename: Marzieh
authors.initials: M
authors.lastname: Moradi
authors.affiliation: Department of Biology, Qom Branch, Islamic Azad University, Qom, Iran.
authors.forename: Mohamadreza
authors.initials: M
authors.lastname: Yazdanian
authors.affiliation: Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, P.O. Box 19615-1178, Tehran, Iran. Electronic address: haghparast@yahoo.com.
authors.forename: Abbas
authors.initials: A
authors.lastname: Haghparast
mesh_terms: D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D007026:Hypothalamic Area, Lateral / Q000187:drug effects / Q000502:physiology*; D008297:Male; D059225:Nociception / Q000502:physiology*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000502:physiology*; D010147:Pain Measurement; D051381:Rats; D017208:Rats, Wistar; D017448:Receptors, Dopamine D2 / Q000502:physiology*; D013469:Sulpiride / Q000494:pharmacology; D017557:Ventral Tegmental Area / Q000187:drug effects / Q000502:physiology*
chemical_list: D018679:Cholinergic Agonists; D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; C113776:dopamine D2L receptor; D013469:Sulpiride; D002217:Carbachol
keywords: Dopamine D2-like receptors; Lateral hypothalamus; Nucleus accumbens; Pain; Rat; Ventral tegmental area