Persistence of flavor neophobia as an indicator of state-dependent retention induced by pentobarbital, stress, and estrus

As fear conditioning paradigms have failed to find state-dependent retention (SDR) in rats dissociated by the estrous state, an attempt was made to establish a paradigm involving the attenuation of flavor neophobia as a more sensitive indicator of SDR. Experiment 1 established that the paradigm did indicate SDR in male rats dissociated by pentobarbital (10 mg/kg). Experiment 2 generalized the utility of the technique by employing an endogenous state, shock-induced stress, as the dissociative state. Having proved to be an indicator of SDR in the first two experiments, the technique was used in Experiment 3 to investigate the possible dissociative characteristics of the estrous state in female rats. Estrus was investigated because, due to the hormonal condition during estrus, it may provide a useful tool in investigating the dissociative aspects of human perimenstrual periodic psychosis. In Experiment 3, using ovariectomized female rats brought into estrus by injection of estrogen and progesterone in a sequence and amount comparable to the natural cycle, estrus was not demonstrated to be dissociative, i.e., did not produce SDR. The implications of these results in relation to perimenstrual periodic psychosis were discussed.