Aversive stimulus properties of the 5-HT2C receptor agonist WAY 161503 in rats.

Serotonin2C (5-HT2C) receptors may influence motivation and reward through effects on the mesocorticolimbic dopamine (DA) system. Previous work from this laboratory indicated that 5-HT2C receptor stimulation does not induce place conditioning when animals are tested in a drug-free state, but does result in decreased locomotor activity and increased frequency thresholds for electrical self-stimulation of the ventral tegmental area (VTA). The present study was conducted to determine whether the 5-HT2C receptor agonist WAY 161503 may induce place conditioning in a state-dependent manner and also whether this compound will induce gustatory avoidance conditioning in the conditioned taste aversion (CTA) paradigm. The effects of the 5-HT2C receptor agonist WAY 161503 in the place conditioning and CTA (two-bottle choice test) paradigms were assessed in male Sprague-Dawley rats. Administration of WAY 161503 (3.0 mg/kg) induced a state-dependent conditioned place aversion and a CTA to saccharin. The differential state dependency of 5-HT2C receptor agonists' effects in place conditioning (state dependent) and CTA (non-state dependent) is consistent with the activation of different brain systems in these two paradigms. The state-dependent effects in place conditioning underscore the need to include controls for state dependency in studies of 5-HT receptor related compounds.