POTENTIAL NEURONAL MECHANISMS OF ESTROGEN ACTIONS IN SYNAPTOGENESIS AND SYNAPTIC PLASTICITY

1. Studies conducted on the rat arcuate nucleus, an area involved in t he development and control of LH and FSH secretion, have shown the exi stence of hormonally regulated developmental sex differences in synapt ic patterns and estrogen-induced synaptic plasticity during adult life . Several questions raised by these findings are examined in this revi ew: 2. The mechanisms of estrogen-regulated developmental synaptogenes is. These include the role of glycocalyx glycoproteins in neuronal mem branes, neural cell adhesion molecules, and insulin-like growth factor I. 3. The relationship among circulating estrogen, gonadotropin level s, and hypothalamic synaptic plasticity. Recent evidence for the role of GABAergic and dopaminergic synaptic inputs and POMC projections fro m the arcuate nucleus to the GnRH cells is discussed. 4. The synaptolo gic basis of age-related failure of positive feedback. The role of the cumulative effect of repeated preovulatory synaptic retraction and re application cycles on sensescent constant estrus is analyzed.