Differential effect of paradoxical sleep deprivation on acquisition and retrieval of conditioned taste aversion in rats

Abstract

Paradoxical sleep deprivation (PSD) was used to interfere with acquisition or retrieval of conditioned taste aversion (CTA). PSD was achieved by confining rats to small pedestals placed on an electrified grid floor. Fifteen-min access to 0.1% sodium saccharin (conditioned stimulus-CS) by water deprived rats was followed 30–120 min later by intraperitoneal injection of lithium chloride (unconditioned stimulus-US, 0.15 M, 2% to 4% body weight). Retention was tested 1 to 5 days later by offering the animal saccharin again. A 24-hr PSD preceding saccharin drinking prevented CTA acquisition. CTA disruption was diminished by a 2-hr, and completely abolished by an 8-hr interval of home cage recovery inserted between the 24-hr PSD and saccharin presentation. CTA was slightly facilitated by 2-hr PSD in the CS-US interval. The 24-hr PSD preceding CS caused the same CTA disruption when followed by free sleep opportunity or by continued PSD in the 2-hr CS-US interval. Twenty-four-hr PSD preceding retention testing slightly improved retrieval of well established CTA. It is concluded that PSD interferes with the formation of the short-term gustatory trace of CTA but does not affect retrieval of CTA engrams. Gradual compensation for the PSD effect on CTA learning by pre-acquisition sleep suggests that the processes responsible for CTA disruption and recovery correspond to depletion and repletion of the same neurotransmitter stores.