Olfactory basis for the delayed onset of maternal behavior in virgin female rats: experimential effects.

A previous study showed that intranasal zinc sulfate (ZnSO4) treatment shortens the latencies for the onset of maternal behavior in nonpregnant rats. The aim of this study was to see whether after recovery from the effects of ZnSO4 treatment, the latencies for maternal behavior increased. In Experiment 1 nonpregnant females were intranasally infused with ZnSO4 or air or were left untreated and exposed to pups starting 48 hr later. Olfactory discrimination tests using chocolate bits were done simultaneously. The ZnSO4 treatment resulted in short latency maternal behavior (1.1 days) compared with latencies of control females (3.8 days), but neither group showed any loss of olfactory discrimination. Three weeks later- ZnSO4-treated females showed increased latencies for all but retrieving, while control groups showed decreased latencies for all maternal behaviors. In Experiment 2, intranasal ZnSO4- and air-treated females were given olfactory discrimination tests under food deprivation, using chocolate bits and guinea pigs pellets. Choice of guinea pig pellets was more severely affected than choice of chocolate bits, but recovery of the discriminations was complete in 4-5 days. The effects of ZnSO4 on maternal behavior and on olfactory discrimination in nonpregnant females were discussed.