Abstract

Glucocorticoids (GCs) secreted by the adrenal glands in response to stress activation of the hypothalamic-pituitary-adrenal axis (HPA) exert a wide spectrum actions that serve to coordinate the organism to a variety of responses in the organism appropriate to the demands of a stressful situation. In a previous study, we have started, using an immunohistochemical process, to map the glucocorticoid receptors (GR) in the diencephalon and in some forebrain regions of the brain of the frog Rana ridibunda. The present study aimed to continue to map GR distribution in the forebrain of the frog, especially in the olfactory bulb and striatum. The results showed that strong labeling was observed in the olfactory bulb areas, notably within the extragranular plexiform layer (EPL), glomerular layer (GL) and mitral cellular layer (ML). Strong immunoreactive cells were also found in the olfactory tubercle (TO) and postolfactory eminence (PE). In addition, GR-immunostained cells were localized in the ventral striatum (VS), in the dorsal striatum (DS), in the medial septum (MS), and in the nucleus accumbenus (NA). In all cases, immunoreaction was observed in both the nucleus and cytoplasm of the neurons and glial cells. These data suggest that GR-expressing neurons of the forebrain components may have a role in mediating the effects of glucocorticoids on frog brain similar to those in mammals and that the regulatory system for modulating the responsiveness of the stress axis (LHPA) may be an evolutionary and ancient regulatory mechanism in all vertebrates.

Key words: Glucocorticoid receptors (GR), Forebrain, LHPA axis, Immunohistochemistry, Rana ridibunda