AGE-ASSOCIATED DECREASE IN SERUM PROLACTIN LEVEL IN MALE-RATS IS UNRELATED TO CHANGES IN ANTERIOR-PITUITARY D(2)-DOPAMINE RECEPTOR AND HYPOTHALAMIC TYROSINE-HYDROXYLASE OR CYCLO(HIS-PRO)

Serum Prolactin level decreases with age in male rats. To unravel the mechanism(s) underlying hypoprolactinemia, we have measured the hypothalamic tyrosine hydroxylase (TH) and cyclo(His-Pro) (CHP) levels and anterior pituitary D2 dopamine receptor (D2-receptor) numbers in aging rats. The changes in hypothalamic TH and CHP, or pituitary D2-receptor binding and mRNA content, however, were not consistent with the observed hypoprolactinemia. These findings suggest that age-associated hypoprolactinemia in wale rats is not directly related to Changes in pituitary D2-receptor, or hypothalamic TH and CHP.