EFFECTS OF B-HT 920 IN THE TAIL-SUSPENSION TEST

The effect of B-HT 920 on mice subjected to the tail-suspension test (TST), a behavioural tool for gauging depression, was studied. During the test, all the animals had bouts of agitation interspersed with periods of immobility but B-HT 920-treated animals exhibited a differentiated behavioural pattern according to the dose employed: at doses selective for dopaminergic (DA) autoreceptor stimulation (50 and 100 μg/kg), the periods of immobility were unaffected, while at higher doses (0.5, 1, 2 and 3 mg/kg), which are also considered to be active on α2-adrenoceptors, they were much shorter, as they are when known antidepressants are administered. Both clonidine (75 and 150 μg/kg) and yohimbine (l and 5 mg/kg), α2-adrenoceptor agonist and antagonist, respectively, increased immobility time, while N-n-propylnorapomorphine, a DA-agonist, at a dose (10 μg/kg) specific for DA autoreceptors, was completely ineffective. Since the behavioural effects of B-HT 920 vary according to the dosage employed, discussion centres on what receptors might conceivably underly these effects and on their preclinical relevance. © 1991 The Italian Pharmacological Society.