Ontogenetic differences in conditioning of an aversion to a gustatory CS with a peripheral US

Rats 5, 10, or 15 days postnatal were given six pairings of an infused sucrose solution and footshock. Conditioned aversion to the sucrose solution was confirmed for the 5- and 10-day-old pups, but no conditioning was evident for the 15-day-old pups (Experiments 1 and 1A). In Experiment 2 the ventral portion of the rat's body was insulated from the shock source in order to isolate its effect on the feet and minimize visceral consequences of the shock. The sucrose-shock conditioning occurred as before. These results may have implications for the postnatal development of cue-consequence specificity, suggesting that such specificity may in part be learned. The present results also raise the possibility that sources of discomfort may be relatively undifferentiated in the perinatal rat.