Long-term effects of a single 24-hour maternal separation on three different latent inhibition paradigms

Basing animal models for psychiatric diseases on purely environmental manip ulations would be a great asset in biological research, such as in the scre ening of antipsychotic drugs, since they preclude possible interference fro m pharmacologically induced deficits. Recent investigations have yielded ev idence that a single 24-h maternal separation (MS) in rats during the stres s hyporesponsive period (SHRP) alters hypothalamic-adrenal-pituitary (HPA) suds response in adult rats and produces long-term behavioral effects, such as deficits in sensorimotor gating (prepulse inhibition) and selective att ention (latent inhibition [LI]), which have been related to schizophrenia. Since there are implications that the age of the pups at the time of separa tion may be a crucial parameter for the neuroendocrine and behavioral effec ts on adult animals, we investigated the effects of a single 24-h MS on pos tnatal day (PND) 4, 9, or 18 in unrelated adult male and female Wistar rats on three paradigms of Ll: conditioned taste aversion (CTA), active avoidan ce (AA), and conditioned emotional response (CER). Whereas there was no eff ect of MS on CER, MS on PND 9 enhanced LI in the CTA paradigm, and MS on PN D 18 disrupted LI in the AA paradigm in males only. Within subjects separat ed on PND 4, males displayed a severe learning deficit in the AA paradigm, and consequently LT was not observed. The results suggest that a single 24- h MS, irrespective of the developmental stage of the pups when separated, d oes not provide a robust animal model for adult disruption of selective att ention similar to that observed in schizophrenia.