Effect of lidocaine administration at the nucleus locus coeruleus level on lateral hypothalamus-induced antinociception in the rat

Role of dopamine D2-like receptors within the ventral tegmental area and nucleus accumbens in antinociception induced by lateral hypothalamus stimulation

“…The findings from this study revealed that unilateral intra-VTA andaccumbal administration of sulpiride, a dopamine D2-like receptor antagonist, significantly attenuated the antinociception induced by chemical stimulation of the LH. The results in the first set of experiments were in agreement with previous studies which showed that inactivation or stimulation of the LH using excitatory drugs like non-specific cholinergic muscarinic agonist (carbachol) can elicit marked antinociception in tail-flick and formalin test models of pain [2,3,6,37]. This area also plays an important role in the modulation of nociceptive transmission at the level of the spinal cord [8].…”

“…Lateral hypothalamus (LH) is the most important source of orexinergic neurons [4,5] that are projected throughout the central nervous system and plays a role in the descending nociceptive modulation. Several studies support the role of LH orexinergic neurons in antinociception, for example, antinociception occurs following LH inactivation [6,7] or electrical stimulation [8] in rats. Additionally, chemical stimulation of the LH with the cholinergic agonist, carbamylcholine chloride (carbachol), increases response latencies on the tail-flick and foot-withdrawal tests (acute models of pain in animals) in rats [6,9].…”

“…Several studies support the role of LH orexinergic neurons in antinociception, for example, antinociception occurs following LH inactivation [6,7] or electrical stimulation [8] in rats. Additionally, chemical stimulation of the LH with the cholinergic agonist, carbamylcholine chloride (carbachol), increases response latencies on the tail-flick and foot-withdrawal tests (acute models of pain in animals) in rats [6,9]. It has been shown that there are correlations between the hypothalamic orexinergic system and the dopamine mesolimbic pathway [3,4,[10][11][12].…”

Blockade of D1-like dopamine receptors within the ventral tegmental area and nucleus accumbens attenuates antinociceptive responses induced by chemical stimulation of the lateral hypothalamus

“…Previous evidence indicated that inactivation or electrical and chemical stimulation of the lateral hypothalamus (LH) can induce antinociceptive response [13,26]. This area has an important role in the modulation of nociception at the level of the spinal cord [1].…”

“…Moreover, dopamine receptors are highly expressed in the VTA and NAc [23,29]. We previously showed that chemical stimulation of the LH by the injection of carbachol induces antinociception and VTA and NAc orexin receptors are involved in this antinociception [4,26]. In addition, another study in our lab revealed that intra-accumbal administration of D1-and/or D2-like receptor antagonists decreased the antinociceptive effects of intra-VTA orexin-A injection and administration of D2-like receptor antagonist had a more remarkable effect than D1-like receptor antagonist [30].…”