The effect of long-term diethylstilbestrol treatment or hyperprolactinemia on the response of the tuberoinfundibular dopamine neurons to elevated prolactin.

Adult male rats were rendered hyperprolactinemic by two different methods. Some animals received subcutaneous implants of diethylstilbestrol (DES) or empty capsules. After 2 months the capsules were removed. Other rats received 3 anterior pituitary homografts under the kidney capsule or had sham surgery. The DES-treated rats were killed 8 months after capsule removal, while pituitary-grafted rats were killed 4 or 12 months after surgery. The DES-treated rats had hyperplastic anterior pituitaries, and both the DES-treated rats and the rats with anterior pituitary homografts were hyperprolactinemic. The activity of the TIDA neurons, as evidenced by dopamine (DA) synthesis in the median eminence (ME), was markedly and comparably elevated in both of these experimental groups of rats when compared to their respective controls. These data: show that the maintenance of hyperplastic pituitaries 8 months after DES withdrawal is not due to impaired function of the TIDA neurons; and provide no evidence for a neurotoxic effect of prolonged hyperprolactinemia on the response of the TIDA neurons to elevated PRL.