Serotonin2C receptors in the ventral pallidum regulate motor function in rats

The ventral pallidum is a limbic brain region that regulates motor function. This region is extensively innervated by serotoninergic neurons from the dorsal raphe nucleus. Serotonergic receptors, including the 5-HT _2C receptor subtype, are located in the ventral pallidum. However, little is known regarding the behavioral consequences of serotonergic transmission in the ventral pallidum, and the role of 5-HT2C receptors has not been studied. To address this paucity, we measured the motoric consequences of injections of 0.33-10 ng of the 5-HT2C receptor agonist MK 212 into the ventral pallidum of adult male Sprague-Dawley rats. We determined that locomotor activity was attenuated by 6.6 ng MK 212, and rearing was attenuated by both 1 and 6.6 ng. The motor suppressant effects of MK 212 were lost at the higher dose of 10 ng, likely reflecting a loss of selectivity of this ligand. These findings indicate negative regulation of motor function by 5-HT2C receptors in the ventral pallidum.