15 research outputs found
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Stimulation of sexual behavior in the male rat by galanin-like peptide
Galanin-like peptide (GALP) is a recently described neuropeptide, which
shares a partial sequence identity with galanin but is derived from a
separate gene. Central injections of GALP stimulate the secretion of
gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) and
induce the expression of Fos in several brain areas known to regulate male
sexual behavior in the rat. We postulated that GALP may also stimulate
sexual behavior in concert with its stimulatory effect on the
hypothalamic-pituitary-gonadal (HPG) axis. To test this hypothesis, we
administered GALP, galanin, or the vehicle (artificial cerebrospinal
fluid, aCSF) alone to sexually experienced male rats and assessed the
effects of these agents on sexual behavior. We observed that compared to
aCSF alone, GALP significantly increased all aspects of male-typical
sexual behavior, whereas galanin inhibited all of these same behaviors. To
examine whether the stimulatory effects of GALP on sexual behavior were
mediated by GALP's stimulatory effects on the HPG axis, we castrated the
same male rats and repeated the behavioral experiment. We found that GALP
maintained its inductive action on male-typical sexual behaviors in the
castrated animals, suggesting that the effects of GALP on sexual behavior
are not the result of GALP's ability to stimulate testosterone secretion.
These observations suggest that GALP neurons are part of the hypothalamic
circuitry controlling sexual behavior in the male rat
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A role for kisspeptins in the regulation of gonadotropin secretion in the mouse
Kisspeptins are products of the KiSS-1 gene, which bind to a G
protein-coupled receptor known as GPR54. Mutations or targeted disruptions
in the GPR54 gene cause hypogonadotropic hypogonadism in humans and mice,
suggesting that kisspeptin signaling may be important for the regulation
of gonadotropin secretion. To examine the effects of kisspeptin-54
(metastin) and kisspeptin-10 (the biologically active C-terminal
decapeptide) on gonadotropin secretion in the mouse, we administered the
kisspeptins directly into the lateral cerebral ventricle of the brain and
demonstrated that both peptides stimulate LH secretion. Further
characterization of kisspeptin-54 demonstrated that it stimulated both LH
and FSH secretion, at doses as low as 1 fmol; moreover, this effect was
shown to be blocked by pretreatment with acyline, a potent GnRH
antagonist. To learn more about the functional anatomy of kisspeptins, we
mapped the distribution of KiSS-1 mRNA in the hypothalamus. We observed
that KiSS-1 mRNA is expressed in areas of the hypothalamus implicated in
the neuroendocrine regulation of gonadotropin secretion, including the
anteroventral periventricular nucleus, the periventricular nucleus, and
the arcuate nucleus. We conclude that kisspeptin-GPR54 signaling may be
part of the hypothalamic circuitry that governs the hypothalamic secretion
of GnRH