Effect of estrogen and neuroleptics on prolactin secretion and immunoreactive prolactin cells

The use of estrogen and dopamine receptor antagonists is associated with elevated prolactin levels and, in rats, chronic estrogen treatment is also associated with lactotroph proliferation. In this study, haloperidol, fluphenazine, sulpiride and metoclopramide, alone or combined with estradiol, were administered to Wistar rats. Pituitary weight, serum prolactin levels and percent of immunoreactive prolactin cells in the anterior pituitary glands were determined at the end of 60 days of treatment. The pituitary weight of rats treated with estrogen alone or in combination with other drugs was significantly higher than the control group. The serum prolactin level was higher than the upper confidence limit in all but three of the 90 treated rats. While in the control group the percent of immunoreactive prolactin cells was 20%, administration of the neuroleptic drugs and metoclopramide increased this percent to approximately 30%, and estrogen alone or in combination with one of the neuroleptic drugs increased it to approximately 40%. The results presented here demonstrate the relationship between prolactin secretion and prolactin cell number when different neuroleptics and related drugs are used.