Blockade of D1/D2 dopamine receptors within the nucleus accumbens attenuated the antinociceptive effect of cannabinoid receptor agonist in the basolateral amygdala

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

“…Additionally, Sheng et al demonstrated that quinpirole microinjection into the ventrolateral orbital cortex produces dose-dependent and raclopride-reversible antinociception in the tail flick test [42]. Haghparast et al showed that the microinjection of D2-like receptor antagonist, sulpiride, into the NAc prevented the antinociceptive responses induced by a cannabinoid receptor agonist into the basolateral amygdala in the tail-flick and formalin tests [29].…”

“…In order to induce acute pain, the heat was applied in succession 3, 5 and 7 cm from the caudal tip of the tail. The thermal intensity of the radiant heat source (45%) was set to produce a baseline TFL between 2 and 4 s. To avoid tissue damage, the trial was automatically terminated if a response did not occur within 10 s (cut-off point) [29,36]. The value of each TFL time was calculated by the average of two consecutive TFL tests in each time point.…”

“…Dopamine agonists such as apomorphine and D-amphetamine produce analgesia during the formalin test as a model of persistent inflammatory pain in rats [29,30]. Intraaccumbal microinjection of dopamine antagonists block the antinociception produced either by pharmacological stimulation of mesolimbic neurons in the VTA, or by a conditioning noxious stimulus [26,31].…”

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

“…Tail-flick response latencies (TFL) were measured during 1-h period at 5, 15, 30, 45 and 60 min after microinjections using a tail-flick apparatus (Harvard, USA) [10,12]. Radiant heat from a projector lamp was applied to the dorsal surface of the rat tails at a distance of 3-7 cm from its tip to evoke the tail-flick reflex.…”

“…Besides, evidence claimed that dopaminergic neurons in the mesolimbic system are mostly involved in the antinociceptive effect of amphetamine and other dopaminergic agonists [29]. Dopamine agonists such as cocaine, amphetamine, apomorphine and quinpirole produce analgesia in formalin test [3,12,31] and these effects are attenuated by either pretreatment with dopamine receptor antagonists or dopaminedepleting 6-OHDA lesions in the VTA [19]. Dopamine receptors classify into two families based on their pharmacological properties: D1-like which includes D1 and closely-related D5 receptors, and D2-like consists of D2 and closely-related D3 and D4 receptors [17].…”