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

• D1 receptors in the VTA and NAc involve in the LH-induced antinociceptive responses.
• Blockade of D1-like receptors in the VTA decreased the LH-induced antinociception.
• Blockade of D1-like receptors in the NAc attenuated the LH-induced antinociception.

It was established that stimulation of the lateral hypothalamus (LH) can induce antinociception. Previous studies showed a role for the ventral tegmental area (VTA) and nucleus accumbens (NAc) in antinociception induced by LH stimulation through the orexinergic system. In this study, we tried to assess the involvement of dopamine D1-like receptors within the VTA and NAc in the LH stimulation-induced antinociception. Male Wistar rats were unilaterally implanted with two separate cannulae into the LH and VTA or NAc. Animals received intra-VTA or intra-accumbal infusion of SCH-23390, as a D1-like dopamine receptor antagonist (0.125, 0.25, 1 and 4 μg/rat), 2 min before intra-LH administration of carbachol (125 nM/rat). The antinociceptive effects of SCH-23390 were measured by using a tail-flick analgesiometer and represented as maximal possible effect (%MPE). Results showed that intra-VTA and/or accumbal administration of SCH-23390 could prevent carbachol-induced antinociception. These findings revealed that D1-like dopamine receptors within the VTA and NAc play an important role in antinociceptive effect induced by chemical stimulation of the LH.