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Leptin’s Actions on the Reproductive Axis: MECHANISMS OF LEPTIN’S ACTIONS ON REPRODUCTION(3)


Although distribution of Ob-R in the brain varies among those species studied thus far (for discussion see ), all species to date express Ob-R mRNA in the arcuate (Arc) and ventromedial nuclei (VMN) of the hypothalamus (Fig. 2A)—two areasacknowledgedtoinfluencebothfeeding and reproductive behaviors. To elucidate the neuronal pathways by which leptin influences reproductive function, we and others have begun to identify the phenotypes of neurons that are responsive to leptin (i.e., express Ob-R) through double-labeling experiments, using both in situ hybridization and immunohistochemistry. antibiotic levaquin

Since leptin has been shown to stimulate GnRH secretion from the basal hypothalamus, it has been proposed that leptin may signal GnRH-containing neurons directly. However, experiments performed in both the rat and the monkey show little coexpression of Ob-R and GnRH at either the protein or mRNA level. Although this lack of evidence does not rule out the possibility of leptin’s direct stimulation of GnRH release, it seems more likely that leptin exerts its actions on GnRH secretion by acting transsynaptically.
Fig2Leptin's Actions on the
FIG. 2. A) Distribution of leptin receptor (Ob-R) mRNA in the female monkey hypothalamus. Areas in the hypothalamus expressing Ob-R mRNA (seen as clusters of white dots) include the VMN, Arc, median eminence (ME), and lateral hypothalamus (not shown). 3V, Third ventricle. Bar = 500 ^m. B) Ob-R mRNA expression in POMC mRNA-expressing neurons in the Arc of the monkey. POMC mRNA-expressing neurons are filled with purple-black precipitate (arrows), and Ob-R mRNA is seen as clusters of white dots. Almost half of all POMC mRNA-containing neurons in the Arc also express Ob-R mRNA. Bar = 30 ^m.