Neonatal domoic acid abolishes latent inhibition in male but not female rats and has differential interactions with social isolation

Abstract

Deficits in attention have long been identified as a core feature in schizophrenia and related neuropsychiatric disorders. We have investigated the combined effects of neonatal treatment with domoic acid (DOM) and social isolation rearing (both putative animal models of schizophrenia) on latent inhibition (LI), a measure of attentional processing. Daily subcutaneous injections of 20 μg/kg DOM or saline were administered to rat pups from postnatal days (PND) 8-14. After weaning, rats were housed either alone or in groups of 4 until LI was assessed at PND 110 using a lick-suppression conditional emotional response paradigm. Neonatal treatment with DOM abolished LI behaviour in adult male rats regardless of housing condition when tested 48 h after conditioning, but this effect was not observed in female rats. Social isolation rearing also reduced LI in male rats, but not to the same extent as DOM. When tested again one week later, single-housed males treated with DOM displayed significant LI whereas saline treated or group-housed DOM males did not. No significant differences were found with females 1 week later. We conclude that neonatal DOM and social isolation both impair attentional processing in young adult male, but not female, rats although the mechanisms by which this occurs appear to be different.

Keywords: Animal models; Attentional processing; Domoic acid; Isolation rearing; Latent inhibition; Schizophrenia.