Estrogen priming affects active membrane properties of medial amygdala neurons.

The medial nucleus of the amygdala (MNA) in the rat is a target tissue for estrogen binding and a sexually dimorphic structure. We used an in vivo slice preparation and intracellular recording techniques to study the effects of beta-estradiol priming on active and passive membrane properties of MNA neurons. Two groups of adult female rats were used; ovariectomized (OVX) non-primed rats and OVX rats that were estrogen-primed at least 24 h prior to recording. Estrogen priming increased the occurrence of spontaneous excitatory postsynaptic potentials (EPSPs) in MNA neurons, and of depolarizing afterpotentials (DAPs) observed with a cathodally triggered action potential, and was associated with a lack of accommodation in these cells. Overall, long-term exposure to estrogen markedly increased the spontaneous activity and excitability of the MNA neurons.