Kisspeptin cells in the ewe brain respond to leptin and communicate with neuropeptide Y and proopiomelanocortin cells

Cannabinoids and Reproduction: A Lasting and Intriguing History

Starting from an historical overview of lasting Cannabis use over the centuries, we will focus on a description of the cannabinergic system, with a comprehensive analysis of chemical and pharmacological properties of endogenous and synthetic cannabimimetic analogues. The metabolic pathways and the signal transduction mechanisms, activated by cannabinoid receptors stimulation, will also be discussed. In particular, we will point out the action of cannabinoids and endocannabinoids on the different neuronal networks involved in reproductive axis, and locally, on male and female reproductive tracts, by emphasizing the pivotal role played by this system in the control of fertility.

Kisspeptin directly regulates neuropeptide Y synthesis and secretion via the ERK1/2 and p38 mitogen-activated protein kinase signaling pathways in NPY-secreting hypothalamic neurons

Kisspeptin is a key component of reproduction that directly stimulates GnRH neurons. However, recent studies indicate that kisspeptin can indirectly stimulate GnRH neurons through unidentified afferent networks. Neuropeptide Y (NPY) is another key reproductive hormone that is an afferent stimulator of GnRH neurons. Herein, we report kisspeptin receptor Kiss1r mRNA expression in native NPY neurons FAC-sorted from NPY-GFP transgenic mice. Thus, we hypothesized that kisspeptin indirectly stimulates GnRH neurons through direct regulation of NPY neurons. Using hypothalamic NPY-secreting cell lines, we determined that kisspeptin stimulates NPY mRNA expression and secretion in the mHypoE-38 cells, but not the mHypoE-42 cells, using quantitative RT-PCR and enzyme immunoassays. Furthermore, agouti-related peptide, ghrelin, neurotensin, or Kiss1r mRNA expression was not changed upon exposure to kisspeptin in either cell line. These results concur with our previous work identifying the mHypoE-38 cell line as a putative reproductive NPY neuron and the mHypoE-42 cell line as a potential feeding-related NPY neuron. In the mHypoE-38 cells, kisspeptin activated the ERK1/2 and p38 MAPK kinases as shown by Western blot analysis. Moreover, inhibiting the ERK1/2 and p38 pathways with U0126 and SB239063, respectively, prevented kisspeptin induction of NPY mRNA expression and secretion. Altogether, we find that kisspeptin directly regulates NPY synthesis and secretion via the ERK1/2 and p38 MAPK pathways in a NPY-secreting cell line, and we propose NPY neurons as an afferent network by which kisspeptin indirectly stimulates GnRH secretion.

Hypothalamic expression of KISS1 and gonadotropin inhibitory hormone genes during the menstrual cycle of a non-human primate

Kisspeptin, the product of the KISS1 gene, stimulates gonadotropin-releasing hormone (GnRH) secretion; gonadotropin inhibitory hormone (GnIH), encoded by the RF-amide-related peptide (RFRP) or NPVF gene, inhibits the reproductive axis. In sheep, kisspeptin neurons are found in the lateral preoptic area (POA) and the arcuate nucleus (ARC) and may be important for initiating the preovulatory GnRH/luteinizing hormone (LH) surge. GnIH cells are located in the ovine dorsomedial hypothalamic nucleus (DMN) and paraventricular nucleus (PVN), with similar distribution in the primate. KISS1 cells are found in the primate POA and ARC, but the function that kisspeptin and GnIH play in primates has not been elucidated. We examined KISS1 and NPVF mRNA throughout the menstrual cycle of a female primate, rhesus macaque (Macaca mulatta), using in situ hybridization. KISS1-expressing cells were found in the POA and ARC, and NPVF-expressing cells were located in the PVN/DMN. KISS1 expression in the caudal ARC and POA was higher in the late follicular phase of the cycle (just before the GnRH/LH surge) than in the luteal phase. NPVF expression was also higher in the late follicular phase. We ascertained whether kisspeptin and/or GnIH cells project to GnRH neurons in the primate. Close appositions of kisspeptin and GnIH fibers were found on GnRH neurons, with no change across the menstrual cycle. These data suggest a role for kisspeptin in the stimulation of GnRH cells before the preovulatory GnRH/LH surge in non-human primates. The role of GnIH is less clear, with paradoxical up-regulation of gene expression in the late follicular phase of the menstrual cycle.