Proceedings of The Physiological Society

Physiology 2016 (Dublin, Ireland) (2016) Proc Physiol Soc 37, PCA247

Poster Communications

Hypothalamic c-Fos/CRF activations during acute stress and expression of β-endorphin fibers in an animal model of perimenopause

A. P. Arikawe1,2, R. Rorato2, L. Elias4, J. Anselmo-Franci3

1. Department of Physiology, University of Lagos, Idi Araba, Lagos, Lagos, Nigeria. 2. Department of Physiology, University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil. 3. Department of Morphology, Physiology and Basic Pathology, University of Sao Paulo, Ribeirao Preto, Sao Paulo, Brazil. 4. Department of Physiology, University of Sao Paulo, School of Medicine, Ribeirao Preto, Sao Paulo, Brazil.


Perimenopause is characterized by neuroendocrine changes that may be involved in how women react to stressful situations. Using an animal model of perimenopause i.e. rats treated with 4-vinylcyclohexene diepoxide (VCD), this study aimed to explore the association of the main central nuclei of stress system (Paraventricular nucleus-PVN and Locus Coeruleus-LC) with acute stress. Progesterone increases the amount of β-endorphin fibers in the LC which inhibit its neurons. As we demonstrated in this animal model that progesterone levels are lower while the response of LC to stress is higher than control rats, we aimed to correlate the neuronal stress response of LC with the amount of β-endorphin fibers. Also, PVN response to stress was analyzed by c-FOS expression. Female rats from 28 days old were injected (SC) daily with VCD (160 mg/kg; VCD group) or Corn oil (2.5 µl/g BW, Control group) for 15 days. At 85-95 days of age at diestrus morning, rats were exposed to 30 min restraint stress followed by 60 min of recovery. Rats were then anaesthetized with a solution of ketamine hydrochloride (55mg/kg BW, IP) associated with xylazine (10 mg/kg BW, IP) and then perfused. Brains were processed immunohistochemically for c-FOS/CRF in PVN and density of β-endorphin fibers in the LC. The increase in number of c-Fos/CRF positive neurons induced by stress in PVN was higher (P < 0.05) while density of β-endorphin fibers in the LC was lower (P < 0.05) in the VCD treated compared to Control rats. These results show that neurons of the stress systems are overactive and suggest that during perimenopause the over reaction of the LC neurons may be due to the lower progesterone levels that induce a decrease of β-endorphin inhibition of LC neurons.

Where applicable, experiments conform with Society ethical requirements