Eliminating the adrenal stress response does not affect sleep deprivation-induced acquisition deficits in the water maze

Sleep deprivation impairs spatial learning in the rat. Sleep deprivation, however, also causes stress and stress itself can interfere with spatial learning. To address this confound, sleep deprivation effects on Morris water maze training were studied in intact rats and in rats in which the adrenal stress response had been eliminated by adrenalectomy. Stable, physiological levels of corticosterone were maintained in adrenalectomized rats with an implanted pellet. Training occurred 6–7 days after surgery. Seventy-two hours sleep deprivation by the platform-over-water method just prior to training slowed, but did not block, learning. In particular, the robust savings between trials 1 and 2 of the first set found in home cage rats was not present in sleep-deprived rats. Adrenalectomy/corticosterone replacement surgery did not modify the effect of sleep deprivation on acquisition rate, demonstrating that the deficits in spatial task acquisition due to pre-training sleep deprivation are not secondary to the adrenal stress response.