Lm. Flanagan-cato et al., The synaptic organization of VMH neurons that mediate the effects of estrogen on sexual behavior, HORMONE BEH, 40(2), 2001, pp. 178-182
Estrogen acts in the hypothalamic ventromedial nucleus (VMH) of female rats
to promote sexual behavior, as typified by the lordosis response. Morpholo
gical changes in the VMH, such as increased synaptic profiles and increased
dendritic spines, suggest that estrogen may modulate behavior by altering
VMH synaptic organization. To understand the significance of these changes,
this laboratory has been investigating the functional classes of lordosis-
relevant neurons and their local connectivity. A neurotropic virus, pseudor
abies virus (PRV), was used to transneuronally label the CNS network that c
ontrols the lordosis-producing muscles. When PRV was placed in the lumbar e
paxial muscles, it was sequentially detected in the lumbar ventral horn, th
e medullary reticular formation, the periaqueductal gray, and finally the V
MH. Subsequent analysis showed that the population of VMH neurons that were
initially infected with PRV largely resided beyond the cluster of estrogen
receptor-containing neurons. In a separate study, VMH neurons were visuali
zed with Lucifer yellow, and their morphology was analyzed using confocal m
icroscopy. Such analysis confirmed that estrogen treatment increased dendri
tic spines in the VMH. The particular VMH neurons in this study did not exp
ress nuclear estrogen receptor, which suggests that estrogen can increase s
pine density indirectly. These results represent initial steps toward unrav
eling the local circuit that mediates estrogenic action on a specific repro
ductive behavior. (C) 2001 Academic Press.