Stimulation of "regulatory" dopamine receptors by bromocriptine (CB-154)

Bromocriptine produces long-lasting hypomotility and decreases brain dihydroxyphenylacetic acid (DOPAC) in mice. These effects are obtained with doses much lower than those which produce hypermotility. The decrease of brain DOPAC is correlated to the hypomotility both on a dose and on a time basis. Potent DA receptor blockers as pimozide, benzperidol and droperidol antagonize the hypomotility and the decrease of brain DOPAC produced by bromocriptine. These effects are obtained with very low doses (0.05-0.3 mg/kg) of neuroleptics which per se do not affect motility or brain DOPAC. The maximal decrease of brain DOPAC produced by bromocriptine is similar to that produced by apomorphine and the combination of these drugs does not result in a further decrease. On the basis of these results it is postulated that bromocriptine decreases DA turnover and produces hypomotility by acting on "regulatory" DA receptors different from the postsynaptic ones of the "terminal" dopaminergic areas.