ActivatIon of Calcium binding protein-ir neurons IN MEDIAL AMYGDALA during chemosignal processing

Functional connectivity of intercalated nucleus with medial amygdala: A circuit relevant for chemosignal processing

Medial amygdala processes social/reproductive chemosensory input, and its projections to preoptic and hypothalamic areas evoke appropriate behavioral and physiological responses. We and others have shown that different chemosensory signals elicit differential responses in medial amygdala subregions and in adjacent main intercalated nucleus (mICN). The largely GABAergic mICN receives no direct chemosensory input but, as we show, mICN has functional circuit connections with medial amygdala that could be responsible both for mICN chemosensitivity and for a feedforward inhibitory effect on posterior medial amygdala; which, in turn would affect chemosignal response. mICN is subject to inhibition by dopamine and is probably regulated by neuropeptides and input from frontal cortex. Thus, mICN is in position to modify chemosensory processing in medial amygdala and behavioral responses to social signals, according to internal brain state. Patch-clamp recordings from neurons in each relevant nucleus in horizontal brain-slices, with electrical stimulation in adjacent nuclei, reveal multiple functional connections between medial amygdala subregions and mICN. We highlight a triangular circuit which may underlie mICN chemosensitivity and its potential for modifying chemosensory information transmitted to basal forebrain. Anterior medial amygdala, which receives most of the chemosensory input, connects to posterior medial amygdala directly and both areas send information on to basal forebrain. Anterior medial amygdala can also modulate posterior medial amygdala indirectly via the mICN side-loop, which also provides a pathway for modulation by cortical input or, when inhibited by dopamine, could allow a more automatic response - as proposed for other amygdala circuits with similar ICN side loops.

Hypothalamic cellular and molecular plasticity linked to sexual experience in male rats and mice

Male sexual behavior is subject to learning, resulting in increased efficiency of experienced males compared to naive ones. The improvement in behavioral parameters is underpinned by cellular and molecular changes in the neural circuit controlling sexual behavior, particularly in the hypothalamic medial preoptic area. This review provides an update on the mechanisms related to the sexual experience in male rodents, emphasizing the differences between rats and mice.