Understanding mechanisms of stress hyporesponsiveness in lactating females. (360G-Wellcome-078955_Z_05_A)

Lactating females show attenuated neuroendocrine and behavioural responses to stress, thereby providing an innate model of stress hyporesponsiveness. We propose that understanding the mechanisms by which neuroendocrine responses to stress are naturally reduced, such as in lactating females, will provide the basis to develop treatments for stress and strategies to avoid stress. We hypothesise that attenuated stress responses during lactation are due to reduced synthesis and secretion of corticotrophin releasing hormone (CRH) and/or arginine vasopressin (AVP) from the hypothalamus as a result of increased negative feedback by cortisols. We also propose that oxytocin produced in the brain facilitates these mechanisms. Previous studies have examined mRNA levels as an index of response, but no-one has measured secretion of CRH and AVP. To test our hypothesis, we will directly measure steady-state levels of CRH and AVP mRNA and secretion of CRH and AVP in lactating and non-lactating females under basal and stress-induced conditions. Furthermore, we will establish the efficacy of cortisol feedback on CRH and AVP synthesis and secretion and will ascertain if oxytocin acts centrally to attenuate neuroendocrine responses to stress.