POSSIBLE IMPLICATION OF TRH AND DOPAMINE IN POSTNATAL LACTOTROPIC INSENSIBILITY

Our results show that pituitary glands of young rats (6 days) incubate d in vitro, increase their PRL secretion in presence of TRH. this resp onses is greater than that in adult glands. Indeed, in presence of TRH 10(-7) M, PRL basal secretion of immature glands passes from 478.70 /- 67.25 to 952.78 +/- 67.02, versus 5333.29 +/- 75.456 and 6347.15 +/ - 75.246 ng/mg protein at mature glands. The same dose of dopamine (DA ), weakens the TRH stimulating effect by 60 % and 40 % respectively by young and adult pituitary glands. These results suggest that lactotro ph insensitiveness to TRH injection observed during the first days of postnatal life at the rat, would not be explained by lactotroph failur e, but by intervention of central and peripheral multiple modulator fa ctors affecting lactotrophs reactivity, in particular the importance o f dopaminergic control.