Endocrine Abstracts

Enhanced corticosterone release by female compared to male rats under basal and stress conditions has been frequently evidenced (1). The demonstration that gonadectomy enhances stress-induced corticosterone secretion in male rats (2) but reduces such levels in female rats (3) suggests a causal association between gonadal steroids and corticosterone release. The present study examined the corticosterone profile of intact and gonadectomised female and male rats under basal and stress conditions. Accordingly, four groups (n=8) consisting of female sham-operated, female ovariectomised, male sham-operated and male castrated Sprague-Dawley rats were used. An automated sampling system collected blood from each freely moving, unanaesthetised rat every ten minutes i) over a twenty-four hour period ii) following noise stress and iii) following an immune-mediated stress (lipopolysaccharide). Plasma was analysed for corticosterone content using radioimmunoassay. Male shams and ovariectomised females had lower corticosterone release over the twenty-four hour period and after each type of stressor compared to female sham and castrated male rats. These results support earlier findings of sexual dimorphism with regard to corticosterone release characterised by increased basal and stress levels for females compared to males. Additionally, they suggest that gonadal hormones influence such heterogeneous corticosterone levels between the sexes with testosterone having an inhibitory effect and female gonadal steroids having an excitatory effect on corticosterone release.

1. Handa, R.J., Burgess, L.H., Kerr, J.E. & O'Keefe, J.A. (1994). Horm. Behav., 28; 464:476.

2. Viau, V & Meaney, M.J. (1996). J. Neurosci., 16; 1866:1876.

3. Burges, L.H. & Handa, R. J. (1992). Endocrinology, 131; 1261:1269.