Asymmetrical distribution of hippocampal mineralocorticoid receptors depends on lateralization in mice.

Previous experiments showed that the activation of the hypothalamic-pituitary-adrenal (HPA) axis during stress was associated with behavioral lateralization used as a marker of population heterogeneity in mice. Furthermore, brain asymmetries have been demonstrated in neurotransmitter metabolism and neuroendocrine modulation. As the hippocampus modulates the activity of the HPA axis in stress and basal conditions, we postulated that hippocampal corticoid receptors may be asymmetrically distributed and that asymmetry may differ according to behavioral lateralization of animals. In order to answer these questions, binding capacity of mineralocorticoid (MR) and glucocorticoid (GR) receptors was determined in right and left hippocampi of mice previously selected for paw preference. The results show that regardless of behavioral lateralization, there was a tendency for a right dominance in MR binding capacity in the hippocampus but interestingly, the percentage of right/ total MR binding capacity was inversely correlated with individual paw preference scores. The affinity of MRs did not depend on behavioral lateralization. GR binding capacity was similar in each hemisphere and no relationship was found between GR binding capacity and paw preference scores. These results suggest that hippocampal receptors for corticoids may play an important role in the asymmetrical brain control of immune reactivity.