Effects of neonatal maternal separation on HVR are no longer present in middle‐aged female rats.

Abstract

Neonatal maternal separation (NMS) disrupts normal neurological development in mammals. The hypoxic ventilatory response (HVR) of adult male rats previously subjected to NMS is ∼25% greater than controls while the response of NMS females is reduced by ∼30% (Genest et al., 2004). To address the role of ovarian hormones on the respiratory phenotype observed in NMS females, we compared the HVR of adult (10–14 weeks old) with that of more mature females (53–60 weeks old) in which circulating estradiol and progesterone levels are significantly reduced. Pups subjected to NMS were placed in an incubator 3h/day for 10 consecutive days (P3 to P12). Controls were undisturbed. Rats were then reared normally until adulthood or middle age when HVR was measured with plethysmography (12% O2, 20 min). The HVR of middle‐aged females was greatly reduced compared to adults. The effects of NMS on HVR were attenuated in middle‐aged compared to younger adult females. Middle‐aged NMS females tended to have a higher HVR than controls, as observed in adult NMS males vs. controls. These results highlight the interaction between endogenous hormones and the respiratory phenotype observed in NMS animals. Supported by the CIHR.