Influence of rearing conditions on the acquisition of the two-way active avoidance responses by rats septalectomized at an early age.

When performed in the adult 3-month old rat, septal lesions facilitated the acquisition of a two-way active avoidance (AA) task as compared to animals sham-operated at the same age. When performed in the 7-day-old rat pup, the same lesion also clearly facilitated the 2-way AA acquisition by the rats when adult and, more especially so, when the rats were isolation-reared from weaning. The performances of these early-septal rats reared in isolation did not differ from those of rats septalectomized at adult age, while the performances of the early-septal rats that had been group-reared from weaning proved to be lower than that of adult-operated rats, with regard to both number of shocks avoided and mean response latencies in the initial phase of acquisition. The improvement of the 2-way AA acquisition following septal lesion may result from an increased responsiveness to aversive stimulation and this responsiveness may be enhanced if the early-septal rats are reared in isolation from weaning.