Effects of early experiences on shock-and illness-induced passive avoidance behaviors.

Abstract

AbstractRats were either handled, shocked, or unmanipulated during the preweaning period or during the 21 days immediately following weaning. At maturity animals were tested in 2 passive avoidance situations. Half the animals were first tested in an illness‐induced taste aversion situation using sour water as the CS and different doses of cyclophosphamide as the US. The remaining animals were first tested in a 1‐trial passive avoidance situation using a “step‐through” apparatus and a single electric shock. Early experience had no effect on the development of a taste aversion at any dosage of cyclophosphamide. Prior conditioning of a taste aversion did influence performance in the step‐through avoidance situation. Fewer of these previously conditioned animals attained the training criterion and, within this previously conditioned population, the handled groups displayed less “emotional” behavior than the controls. Response latencies in the shock‐induced passive avoidance test did not differentiate between handled and shocked animals. Animals manipulated prior to weaning had consistently shorter latencies than the unmanipulated controls.