Synaptogenic effect of estrogen on the hypothalamic arcuate nucleus of the adult female rat
Matsumoto, A.; Arai, Y.
Cell and Tissue Research 198(3): 427-433
ISSN/ISBN: 0302-766X PMID: 466679 DOI: 10.1007/bf00234187
To examine the effect of estrogen on the synaptic structures in the hypothalamic arcuate nucleus (ARCN), semiquantitative studies were performed by counting synapses in an 18,000 .mu.m2 area in the middle of the ARCN in each brain. In ovariectomized female rats injected with 2 .mu.g of estradiol benzoate (EB) for 3 wk, the mean numbers of axodendritic and axosomatic synapses were not significantly different from those in the intact and ovariectomized controls. When the medial basal hypothalamus (MBH) including the ARCN was isolated by use of a Halasz knife (MBH island), the mean number of axodendritic synapses was decreased to about half of the controls. EB treatment for 3 wk from the day of surgery effectively restored the axodendritic synaptic population of the deafferented ARCN. Estrogen apparently has a facilitatory effect on axodendritic synapse formation in the deafferented ARCN, presumably by stimulating axonal sprouting and synaptic regeneration of intact axons in the MBH island.