Quantitative changes in reduced nicotinamide adenine dinucleotide phosphate-diaphorase-reactive neurons in the brain of Octodon degus after periodic maternal separation and early social isolation

The influence of preweaning maternal separation and postweaning social isol ation on the development of reduced nicotinamide adenine dinucleotide phosp hate (NADPH)-diaphorase-reactive neurons in prefrontal cortical areas, in s ubdivisions of the nucleus accumbens and in the corpus callosum was quantit atively investigated in the precocious rodent Octodon degus. Forty five-day -old degus from three animal groups were compared: (i) degus that were rear ed under normal undisturbed social conditions; (ii) degus that were repeate dly separated from their mothers during the first three postnatal weeks and thereafter reared with their family; and (iii) degus that remained undistu rbed with the family until weaning (postnatal day 21) and thereafter were r eared in social isolation. Preweaning maternal separation led to a signific ant decrease in NADPH-diaphorase-containing neurons in the corpus callosum in both genders (down to 33%) compared with the social control group. No si gnificant changes were found in the subregions of the medial prefrontal cor tex and nucleus accumbens. Postweaning social isolation led to a reduced de nsity of NADPH-diaphorase-containing neurons in the corpus callosum in both genders (down to 52%) compared with the social control group. Furthermore, in the precentral medial cortex of female pups, a significant reduction in NADPH-diaphorase-reactive neurons (down to 72%) was detectable. All other regions of the medial prefrontal cortex and the nucleus accumbens remained unchanged. The observed deprivation-induced changes may reflect either an e xcessive reduction in NADPH-diaphorase-positive neurons or a down-regulatio n of the enzyme in neurons that normally express it. Our results indicate a link between early adverse socio-emotional experienc e and the maturation of NADPH-reactive neurons. Further studies are require d to analyse the functional implications of this experience-induced brain p athology. (C) 2000 IBRO. Published by Elsevier Science Ltd. All rights rese rved.