Sexual excitement and stretching and yawning induced by B-HT 920

The azepine derivative B-HT 920, a putative agonist at dopamine (DA) autoreceptors, injected IP in adult male rats, induced numerous penile erections (PE) and stretching and yawning (SY), considered typical signs of central DA receptor stimulation, without eliciting stereotyped behaviour (SB). Both signs induced by B-HT 920 were dose related and significantly enhanced with respect to controls from 10 to 1,000/micrograms/kg. Pretreatment with the neuroleptics haloperidol (0.025, 0.5 and 1 mg/Kg IP), sulpiride (20 and 40 mg/Kg) and alpha 2-antagonist yohimbine (1 and 3 mg/Kg IP) antagonized the behavioural effect of B-HT 920 whereas the alpha 1-antagonist prazosin (1 mg/Kg IP) had no effect on the response. The impressive activity of B-HT 920 in producing SY and PE, along with its inability to evoke SB, supports the role of DA autoreceptors in the regulation of SY and sexual behaviour.