INVOLVEMENT OF THE SEROTONERGIC SYSTEM IN ETHANOL INTAKE IN THE RAT

A two-bottle, free-choice paradigm was used to investigate the influen ce of the serotonergic (5-HT) system on ethanol intake in genetically heterogeneous Wistar rats. Systemic administration of the 5-HT1A agoni st ipsapirone (1.25-5.0 mg/kg) caused a dose-dependent decrease in eth anol preference and intake, while the 5-HT2 antagonist ritanserin (1.2 5-5.0 mg/kg) and the 5-HT3 antagonists ondansetron (0.01-1.0 mg/kg) an d granisetron (0.5-1.0 mg/kg) failed to alter ethanol consumption. The effect of ipsapirone treatment on ethanol intake was more pronounced in high-preferring animals than in low-preferring. A closer look at th e microstructure of the rat's drinking behaviour by means of a microco mputer-controlled data acquisition system showed that ipsapirone treat ment caused a significant decrease in the number of licks recorded at the ethanol-containing bottle and a decrease in the time spent at this bottle. Furthermore, ipsapirone treatment caused a significant increa se in the number of breaks in licking behaviour recorded at this bottl e. The drinking behaviour at the water-containing bottle was not affec ted by the ipsapirone treatment. Neither was the rat's eating behaviou r altered by this treatment. These findings support the hypothesis tha t the 5-HT system is involved in the regulation of ethanol intake, wit h special emphasis on the involvement of the 5-HT1A receptor subtype, and may indicate that central reward-mediating mechanisms are influenc ed.