Effects of central norepinephrine depletion on the initiation and maintenance of maternal behavior in the rat.

The catecholaminergic neurotoxin, 6-hydroxydopamine (6-OHDA), was used to test the hypothesis that increased transmission across selected noradrenergic synapses is involved in the initiation of maternal behavior. Specifically, 6-OHDA was infused intraventricularly either two days before parturition or four days after parturition. Control animals were infused with the vehicle alone. Among prepartum animals, NE depletion of more than 30% of control levels interfered with the initiation of maternal behavior. Among lactating animals, similar degrees of NE depletion had no significant effect on the maintenance of maternal behavior. Thus, NE appears to be involved in the initiation of maternal behavior, but not in the maintenance of the behavior once that behavior is established.