Hippocampal glucocorticoid receptor and behavior: a correlative study in rats and mice

A correlation has been demonstrated between binding capacity for [3H]corticosterone in the hippocampus and the performance in passive and active avoidance in the rat, and impaired behavior in adrenalectomized rats by exogenous corticosterone is restored. On this basis we have studied the possible correlation between strain-dependent behavioral differences and the glucocorticoid binding capacity in the hippocampus in mice and rats. In Naples high- (NHE) and low-excitability (NLE) rat strains, genetically selected on the basis of divergent locomotor activity upon forced exposure to a spatial novelty situation, no differences were found in glucocorticoid maximal binding capacity while both strains had a lower capacity than Naples random-breed (NRB) control rats. However, the intra-strain correlative analysis of hippocampal glucocorticoid receptors number and behavioral scores demonstrated that motor and emotional indexes of arousal to novelty were positively correlated in NLE-and negatively in NHE- while no correlation was present in NRB rats. Using two inbred strains of mice, C57BL/6 and Balb/c, extensively investigated for learning abilities, the lower active avoidance score of C57BL/6 was associated with a lower binding capacity for [3H]corticosterone in the hippocampus. Altogether the above results support the involvement of the hippocampal glucocorticoid receptor in the modulation of some adaptive behavioral responses, while do not prove that genetic differences in behavior rest on parallel differences in binding capacity for glucocorticoid hormone.