Abstract
Abstract
Serum prolactin and LH levels were measured at several times during pseudo-pregnancy (PP) in the rat and compared to levels found in rats during diestrous Day 2. In the same rats, tyrosine hydroxylase (TH) activity and dopamine-β-hydroxylase (DBH) activity were measured in the median eminence area as indices of dopaminergic and noradrenergic neuronal activity, respectively. Serum LH and median eminence DBH were unchanged throughout the experiment. Serum prolactin was elevated at 1800 hr on Days 4 and 8 of PP and at 0100 hr on Days 5 and 9 compared to unstimulated controls. During the intersurge time (2200 hr) prolactin levels were low but slightly higher than controls. Tyrosine hydroxylase activity in the median eminence was low during the diurnal and nocturnal prolactin surges compared to unstimulated controls. It is concluded that the acute increases in prolactin levels in the blood that occur twice daily during PP may be related to the decrease in activity in dopamine containing neurons that occurs at that time.
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