Behavioural effects in mice of subchronic buspirone, ondansetron and tianeptine. I. Social interactions.

In a continuation of recent work on effects of a benzodiazepine (chlordiazepoxide) and selective monoamine reuptake inhibitors (maprotiline and fluvoxamine), the current study compares effects of the 5-HT1A receptor partial agonist, buspirone (0.75-3.0 mg/kg), the 5-HT3 receptor antagonist, ondansetron (0.1-100 micrograms/kg) and the novel antidepressant, tianeptine (2.5-10.0 mg/kg). Compounds were given daily to mice for 21 days prior to testing and the subsequent behaviour of the animals during social interactions was assessed by ethopharmacological procedures. Buspirone, at 0.75 mg/kg, increased immobility and reduced occurrence of the aggressive act, "attack." At 1.5 and 3.0 mg/kg, it enhanced olfactory exploration of the sawdust substrate, but had no effect on social investigation. Ondansetron increased the duration of environmental exploration at 0.1 microgram/kg, while at 100 micrograms/kg it increased the duration of digging in the substrate. Ondansetron had no effect on the categories of behaviour and failed to induce an anxiolytic-like enhancement of social investigation. Tianeptine produced an anxiogenic-like effect at 10 mg/kg, while at 5 mg/kg it enhanced flight and immobility. The relevance of these findings is discussed in relation of the reported behavioural actions of these compounds and to current pharmacotherapy of anxiety and depression. The apparent anxiogenic effect of tianeptine is a novel finding which requires further study.