Bromocriptine inhibits growth hormone release from rat pituitary cells in primary culture

The action of the potent dopamine receptor agonist bromocriptine was studied in primary cultures of rat anterior pituitary cells. Bromocriptine inhibited both prolactin and growth hormone release in a concentration-dependent manner. This effect was blocked by the dopamine receptor antagonist spiperone when the agonist and antagonist were added coincidently. In contrast, spiperone was unable to affect the actions of bromocriptine if added 1 min after bromocriptine application or later. These results suggest that dopamine receptors exist not only on mammotrophs, but also on somatotrophs in vitro.