Regional difference in sexually dimorphic synaptic organization of the medial amygdala.

The existence of sexual dimorphism in synaptic pattern is demonstrated in the molecular layer of the medial nucleus of the rat amygdala by semiquantitative electron microscopic analysis on synaptic density. Sex difference in synaptic number was found in dendritic shaft synapses in the medial part of the molecular layer, whereas the difference occurred in dendrite spine synapses in the ventral molecular layer. The present study also provides evidence for the involvement of sex steroids in the development of sexually dimorphic neuronal circuitry in the molecular layer.