Dopamine receptor blocking action of a dibenzothiepin derivative isofloxythepin in rats.

1. Subcutaneous injection of isofloxythepin or haloperidol inhibited exploratory behaviour, methamphetamine (3 mg/kg)-induced hyperactivity and bromocriptine (15 mg/kg)-induced yawning, and also elicited catalepsy. 2. Isofloxythepin and haloperidol increased concentrations of dihydroxyphenylacetic acid in the striatum and elevated serum prolactin levels. 3. The results suggest that isofloxythepin, as well as haloperidol, blocks the action of the dopamine D2-receptors in the striatum, nucleus accumbens and pituitary.