EFFECTS OF ESTROGENS AND PROGESTERONE ON THE SYNAPTIC ORGANIZATION OF THE HYPOTHALAMIC VENTROMEDIAL NUCLEUS

• Type: Article in International Scientific Journal
• Date: 2009

Authors

Sa, SI (Author) FMUP; Lukoyanova, E (Author) Other; Madeira, MD (Author) FMUP

Journal

Title: Neuroscience

Vol. 162

Pages: 307-316

ISSN: 0306-4522

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 25 Citations

Scopus - 25 Citations

Scientific classification

FOS: Medical and Health sciences > Basic medicine

Other information

Authenticus ID: P-003-GPY

DOI: 10.1016/j.neuroscience.2009.04.066

Abstract (EN): The majority of the studies on the actions of estrogens in the ventrolateral part of the hypothalamic ventromedial nucleus (VMNvI) concern the factors that modulate the receptive component of the feminine sexual behavior and the expression of molecular markers of neuronal activation. To further our understanding of the factors that regulate synaptic plasticity in the female VMNvI, we have examined the effects of estradiol and progesterone, and of estrogen receptor (ER) subtype selective ligands on the number of dendritic and spine synapses established by individual VMNvI neurons and on sexual behavior. In contrast to earlier studies that analyzed synapse densities, our results show that exogenous estradiol increases the number of spine as well as of dendritic synapses, irrespective of the dose and regimen of administration. They also reveal that an effective dose of estradiol administered as one single pulse induces the formation of more synapses than the same dose administered as two pulses on consecutive days. Our results further show that both ER subtypes are involved in the mediation of the synaptogenic effects of estrogens on VMNvI neurons since the administration of the selective ER alpha, propyl-pyrazole-triol (PPT), and ER beta, diarylpropionitrile (DPN), agonists induced a significant increase in the number of synapses that, however, was more exuberant for PPT. Despite its relevant role in feminine sexual behavior, progesterone had no synaptogenic effect in the VMNvI as no changes in synapse numbers were noticed in rats treated with progesterone alone, with estradiol followed by progesterone or with the antiprogestin mifepristone (RU486). Except for the sequential administration of estradiol and progesterone, none of the regimens was associated with lordosis response to vaginocervical stimulation. Therefore, from the sex steroids that undergo cyclic variations over the estrous cycle, only estrogens, acting through both ER alpha and ER beta, play a key role in the activation of the neural circuits involving the ventromedial nucleus of the hypothalamus.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10