Stimulus properties of fluvoxamine in a conditioned taste aversion procedure

A conditioned taste aversion (CTA) procedure in mice was used to investigate the stimulus effects of the serotonin reuptake inhibitors (SSRIs) fluvoxamine and fluoxetine. Fluvoxamine elicited a reliable CTA (ED(50) = 24 mg/kg, SC) and a number of drugs were tested as pre-exposure drugs. Pre-exposure to the serotonin (5-HT)(1A) receptor agonists flesinoxan and +/--8-hydroxy-dipropylaminotetralin (8-OH-DPAT) prevented the CTA induced by fluvoxamine (50 mg/kg, SC). Pre-exposure with the 5-HT(2C) receptor agonist MK 212 [6-chloro-2(1-piperazinyl)pyrazine] partially prevented the fluvoxamine-induced CTA, pre-exposure with the 5-HT(2A/2C) receptor agonist DOI [1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl] did not prevent the CTA induced by fluvoxamine. Flesinoxan pre-exposure also prevented the taste aversion induced by fluoxetine (10 mg/kg, SC) completely. This contrasts previous results obtained with fluoxetine, where was found that its stimulus is primarily mediated by 5-HT(2C), and to a lesser degree by 5-HT(1A) receptors. Therefore, we compared the two SSRIs directly. Pre-exposure to fluvoxamine prevented the fluoxetine-induced CTA, whereas pre-exposure to fluoxetine only partially prevented the fluvoxamine-induced CTA. We conclude that 5-HT(1A) receptors are involved in the stimulus properties of both fluvoxamine and fluoxetine, that 5-HT(2C) receptors are involved in fluvoxamine and especially fluoxetine, and, based primarily on the cross-comparison tests, that the two SSRIs have somewhat different stimulus properties.