Organizational action of estrogen on synaptic pattern in the amygdala: implications for sexual differentiation of the brain.

Estrogen markedly promotes the specific formation of dendritic shaft synapses in the medial amygdaloid nucleus (AMN) of the rat when given in early postnatal days. The high incidence of this type of synapse permanently persists until sacrifice at adult ages. The data provide evidence for the synaptic plasticity of the developing amygdala to estrogen and suggest a possible morphological mechanism for sexual differentiation of the brain.