Serotonin stimulates prolactin secretion in the hypophysectomized adenohypophyseal grafted rat

Abstract

Normal male, estrogen [estradiol-17.beta.] (F2) primed male and hypophysectomized adenophypophyseal grafted male rats (HAG rats) were used in the experiments. Serotonin creatinine sulfate was injected as a bolus via an indwelling atrial cannula in the conscious free moving rat. Serotonin caused a dose-dependent increase in plasma prolactin (Prl) in normal (1, 3 and 10 mg/kg serotonin) and E2 primed (1 and 3 mg/kg serotonin) male rats that began immediately after injection and reached a peak within 12-15 min of injection. E2 priming significantly increased the magnitude of the response to serotonin. To analyze the site of action of serotonin in the rat, serotonin (1 mg/kg) was injected into HAG rats. Serotonin increased plasma Prl in this rat preparation, indicating that serotonin acts directly on the ectopic pituitary.