Abstract
Studies were performed to determine if apomorphine (APO), a specific dopamine receptor stimulant, was able to influence serum prolactin levels in vivo and in vitro. Administration of APO (ip, 20 mg/kg) to rats with normal 4-day estrous cycles reduced serum prolactin levels during diestrus and prevented the proestrous rise of serum prolactin. The elevation of serum prolactin observed after chlorpromazine treatment (2.5 or 1 /mg) was significantly attenuated by APO. In addition, treatment: of lactating rats with 15 mg/kg of APO prevented the suckling-induced rise of serum prolactin. These observations demonstrate that dopamine receptor stimulation results in inhibition of prolactin secretion in vivo. Incubation of pituitary halves in vitro with 8 + 10−8M (25 ng/ml) APO consistently resulted in a significant decrease in the amount of prolactin released by the pituitary tissue. Concentrations of APO as low as 1.6 + 10−8M (5 ng/ml) were effective.Pimozide, a specific dopamine antagonist, was able to reduce the...
Published Version
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