Differential effect of prior paradoxical sleep deprivation on conditioned taste aversion, neophobia and attenuation of neophobia to solid food in rats

Abstract

The effect of paradoxical sleep deprivation (PSD) on subsequent acquisition of conditioned taste aversion (CTA) to liquid diets is confounded by the uncertain level of thirst when using the water tank procedure. This difficulty is eliminated when examining CTA and attenuation of neophobia (AN) to solid diets. Adult male rats ( n = 100) were habituated to receive their daily ration of food during a 30-min stay in a box equipped with a row of 10 feeders baited with 2–3 g pieces of moist standard diet. 24-h PSD increased neophobic rejection of novel sweet food (with added 5% saccharose), but did not influence intensity of CTA elicited by LiCl poisoning. Addition of a bitter tasting red food dye to the sweet food caused marked neophobia which was enhanced by preceding PSD. Association of this unpalatable food with LiCl elicited strong CTA which extinguished faster in the PSD-pretreated animals. On the other hand, preacquisition PSD did not influence AN to the same stimulus. Sweet food with added blue dye elicited only mild neophobia which was enhanced by preceding 24-h PSD. Preacquisition PSD did not influence AN but significantly increased CTA to blue sweet food. It is concluded that PSD can either enhance or weaken CTA and that this complex effect on food selection learning cannot be explained by PSD-induced reduction of fear.