Effects of neonatal ACTH4-10 administration on adult adaptive behavior and brain tyrosine hydroxylase activity

The effects of daily injection of ACTH4-10 in postnatal days 2-8 were studied on adult adaptive behavior and brain TH activity in male rats. Four groups were used: (1,2) 10 and 2 nmol ACTH4-10 injected, (3) saline injected, and (4) intact, unhandled. The peptide did not influence acquisition but delayed extinction of CAR in the shuttle-box and facilitated passive avoidance behavior against saline control. The experimental manipulation in the saline control group (neonatal stress) also significantly influenced these behavioral variables and motility during conditioning but in the opposite direction as did ACTH4-10 treatment. It was concluded that ACTH4-10 interfered with the action of neonatal stress on the development of adaptive behavior. A similar kind of interaction could also be observed in TH activity of striatum and locus ceruleus but not in all brain areas investigated.