Seasonal changes in basal and stress-induced cortisol levels in the subterranean rodent Ctenomys talarum: differences between sexes and reproductive condition

VERA, FEDERICO; ZENUTO, ROXANA; ANTENUCCI, CARLOS DANIEL

Alessandría

Congreso; 27th ESCPB Congress; 2010

New European Society for Comparative Physiology

The activation of the hypothalamic-pituitary-adrenal (HPA) axis is one of the hallmarks of the stress response in vertebrates. The resulting secretion of glucocorticoids (GCs) is used to monitor stress in natural populations because they reflect physiological adjustments to changing environmental conditions, intra and inter-specific interactions and human disturbance. Despite changes in HPA activity influence survival and reproduction; studies on GCs are scarce in free-ranging animals. Here, we evaluated seasonal changes in basal and stress-induced cortisol levels in Ctenomys talarum, to assess differences between sexes and reproductive condition, and their utility as indicators of stress. During reproductive and non-reproductive seasons we obtained, in the field, baseline blood samples and also subjected other animals to immobilization to obtain cortisol levels in response to stress. We also determined leukocyte profiles to address the significance of seasonal changes in cortisol levels. Both sexes had higher basal plasma cortisol levels during the breeding season, but cortisol levels were 2–3-fold higher in females than males during the breeding cycle. In spite of their high basal cortisol concentration during the reproductive season, females respond to acute stress reaching very high cortisol concentrations after the treatment in this season. These results suggest physiological differences in the HPA axis between sexes and show that adjustments in the output of this neuro-endocrine axis occur seasonally concurrently with changes in reproductive activity. We show that GC concentrations should be coupled with the determination of other stress indicators (leukocyte profiles) to allow a broad understanding of seasonal variation in HPA axis activity