Bromocriptine enhances feeding behavior without changing dopamine metabolism.

Bromocriptine is an ergot derivative and has been thought to act as a selective D2 receptor agonist, but its effects on dopamine release in vivo have not been confirmed. We administered bromocriptine into the striatum of rats and studied the effects on feeding behavior and dopamine release. Bromocriptine was perfused via a microdialysis probe into the ventrolateral striatum of rats fasted for 22 h, and the rats were then allowed to feed freely for 6 h. Bromocriptine perfusion increased food intake in a dose-dependent manner, whereas the extracellular concentrations of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) did not change. Perfusion of (-) sulpiride, a selective D2 receptor antagonist, decreased food intake, but increased dopamine release and the levels of DOPAC and HVA. Pretreatment with (-)sulpiride perfusion for 1 h prior to bromocriptine perfusion inhibited the increase of food intake induced by bromocriptine, and it increased dopamine release and the levels of DOPAC and HVA. These findings suggest that bromocriptine directly perfused into the ventrolateral striatum acts selectively on postsynaptic D2 receptors and enhances feeding behavior.