Dopamine and bromocriptine inhibit cyclic AMP accumulation in the anterior pituitary: the effect of cholera toxin.

Although dopamine clearly inhibits prolactin release from the anterior pituitary gland, the biochemical events occurring subsequent to the activation of the dopamine receptor are poorly understood. We have shown that dopamine reduces the concentration of cyclic AMP within 5 min in primary cultures of rat anterior pituitary cells. This action could be blocked with pretreatment of the cells with the dopamine antagonist spiperone. The long-lasting dopamine agonist bromocriptine also reduced cyclic AMP accumulation in parallel with the inhibitory effect of this drug on prolactin release. Cholera toxin enhanced prolactin release and cyclic AMP content of the anterior pituitary cells, but did not totally annul the efficacy of dopamine or bromocriptine to inhibit prolactin secretion and cyclic AMP accumulation.