Involvement of D1/D2 dopamine receptors within the nucleus accumbens and ventral tegmental area in the development of sensitization to antinociceptive effect of morphine

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

“…Our findings showed that intra-VTA and intraaccumbal microinjection of SCH-23390, as a dopamine D1-like receptor antagonist, prior to intra-LH microinjection of carbachol could inhibit the antinociception induced by chemical stimulation of the LH. Administration of SCH-23390 into the VTA at the doses of 0.25, 1 and 4 g decreased antinociception induced by chemical stimulation of the LH and the maximum effect was observed at the In agreement with our results, previous reports indicated that intra-accumbal administration of D1-like dopamine receptors antagonist decreased the antinociceptive effects of morphine in morphine sensitized rats [23]. Moreover, administration of SCH-23390 systemically attenuated the analgesia induced by amphetamine, morphine and cocaine in the formalin test [14,19].…”

“…Moreover, administration of SCH-23390 systemically attenuated the analgesia induced by amphetamine, morphine and cocaine in the formalin test [14,19]. Microinjection of D1-and D2-like receptor antagonists into the NAc could prevent the antinociceptive effects induced by morphine in the tail flick test [23]. Additionally, Yazdi-Ravandi et al showed that intra-accumbal injection of D1-and/or D2-like receptor antag- onists decreased the antinociceptive effects of intra-VTA orexin-A injection in tail-flick test and administration of D2-like receptor antagonist had a more considerable effect than D1-like receptor antagonist [30].…”

“…Systemic administration of selective dopamine D1-and D2-like receptor agonists attenuates formalin-induced nociceptive behaviors in rats [20]. 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].…”

“…The LH, through the orexinergic projections, is associated with many areas involved in antinociception such as the ventral tegmental area (VTA) and nucleus accumbens (NAc) [5,25]. Numerous studies clarified that the orexinergic projections from the LH to the VTA and NAc are directly/indirectly involved in antinociception induced by chemical stimulation of the LH [4,23,25,28]. In addition, there is a functional interplay between the orexinergic system and mesolimbic dopaminergic pathway [4,21,25,30] and it was shown that orexinergic projections from the LH to the VTA stimulate the release of dopamine in mesolimbic areas such as the NAc [21].…”

Microinjection of the mGluR5 antagonist MTEP into the nucleus accumbens attenuates the acquisition but not expression of morphine-induced conditioned place preference in rats

“…Injections were made bilaterally over a 50 s period, and the injection cannulae were left in the guide cannulae for an additional 60 s in order to facilitate the diffusion of the drugs. The microinjection time for 0.1 μl volume of drugs was 10 s for preventing lesions in these areas (Karimi et al, 2014;Reisi et al, 2014).…”