Is there a critical developmental `window' for isolation rearing-induced changes in prepulse inhibition of the acoustic startle response?

Abstract

In a previous study, rats reared in isolation from weaning exhibited normal prepulse inhibition (PPI) before puberty, whilst after puberty (6–8 weeks post weaning) isolation reared rats exhibited deficits in PPI. The developmental timing of the onset of this isolation effect appears to be critical because similar isolation of adult rats has no effect on PPI. The present study examined the time and duration of the period or `window' of isolation necessary to induce these behavioral changes. Male Sprague–Dawley rats were isolated for either only the first 2 weeks from weaning, only the first 4 weeks from weaning, only weeks 3 and 4, or continuously from weaning (ISO group), and compared with rats reared in normal social conditions (SOC group). Eight weeks after weaning, we compared acoustic and airpuff startle reactivity, acoustic and light PPI, and acoustic and airpuff startle habituation across the groups. There were no significant changes in any of the measures in the groups exposed to 2- or 4-week periods of isolation. In the ISO and SOC groups, acoustic or airpuff startle reactivity was similar, while acoustic PPI was reduced significantly in the ISO group. Airpuff startle habituation was increased significantly in the ISO group compared to SOC controls and there was a similar trend with acoustic startle habituation. These results indicate that only animals isolated for more than 4 weeks after weaning display deficits in PPI, and provide evidence that there is no critical pre-pubertal developmental window for inducing PPI deficits, rather, continuous post-weaning isolation is needed to induce the PPI deficit effect.