Potentiation of dopamine receptor-mediated responses by B-HT 920 in mice

The effect of B-HT 920, an alpha 2-agonist, on postsynaptic dopamine receptor-mediated stereotypic behaviour, was studied in mice. Apomorphine produced typical stereotypic responses in mice such as sniffing, rearing, biting, licking and grooming. B-HT 920, when given alone, produced mild stereotypy. Pretreatment with B-HT 920 significantly potentiated the stereotypic behaviour of apomorphine. The specific alpha 2-blockers, idazoxan and yohimbine, failed to block the potentiating effect of B-HT 920. The specific D2-receptor blockers haloperidol and molindone, completely blocked the stereotypic responses due to B-HT 920 and apomorphine. On reserpinization of animals there was a 5-fold increase in stereotypy induced by the combination of apomorphine and B-HT 920. B-HT 920 also potentiated amphetamine-induced locomotor responses in mice in a haloperidol-sensitive way. These data imply an interaction of B-HT 920 with postsynaptic dopamine receptors.