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

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 developm ental timing of the onset of this isolation effect appears to be critical b ecause similar isolation of adult rats has no effect on PPI. The present st udy examined the time and duration of the period or 'window' of isolation n ecessary to induce these behavioral changes. Male Sprague-Dawley rats were isolated for either only the first 2 weeks from weaning, only the first 4 w eeks from weaning, only weeks 3 and 4, or continuously from weaning (ISO gr oup), and compared with rats reared in normal social conditions (SOC group) . Eight weeks after weaning, we compared acoustic and airpuff startle react ivity, acoustic and light PPI; and acoustic and airpuff startle habituation across the groups. There were no significant changes in any of the measure s in the groups exposed to 2- or 4-week periods of isolation. In the ISO an d SOC groups, acoustic or airpuff startle reactivity was similar, while aco ustic PPI was reduced significantly in the ISO group. Airpuff startle habit uation was increased significantly in the ISO group compared to SOC control s and there was a similar trend with acoustic startle habituation. These re sults indicate that only animals isolated for more than 4 weeks after weani ng display deficits in PPI, and provide evidence that there is no critical pre-pubertal developmental window for inducing PPI deficits, rather, contin uous post-weaning isolation is needed to induce the PPI deficit effect. (C) 1999 Elsevier Science B.V. All rights reserved.