title: Kisspeptin depolarizes gonadotropin-releasing hormone neurons through activation of TRPC-like cationic channels.
abstract: Kisspeptin and its cognate receptor, GPR54, are critical for reproductive development and for the regulation of gonadotropin-releasing hormone (GnRH) secretion. Although kisspeptin has been found to depolarize GnRH neurons, the underlying ionic mechanism has not been elucidated. Presently, we found that kisspeptin depolarized GnRH neurons in a concentration-dependent manner with a maximum depolarization of 22.6 +/- 0.6 mV and EC(50) of 2.8 +/- 0.2 nM. Under voltage-clamp conditions, kisspeptin induced an inward current of 18.2 +/- 1.6 pA (V(hold) = -60 mV) that reversed near -115 mV in GnRH neurons. The more negative reversal potential than E(K)(+) (-90 mV) was caused by the concurrent inhibition of barium-sensitive, inwardly rectifying (Kir) potassium channels and activation of sodium-dependent, nonselective cationic channels (NSCCs). Indeed, reducing extracellular Na(+) (to 5 mM) essentially eliminated the kisspeptin-induced inward current. The current-voltage relationships of the kisspeptin-activated NSCC currents exhibited double rectification with negative slope conductance below -40 mV in the majority of the cells. Pharmacological examination showed that the kisspeptin-induced inward currents were blocked by TRPC (canonical transient receptor potential) channel blockers 2-APB (2-aminoethyl diphenylborinate), flufenamic acid, SKF96365 (1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride), and Cd(2+), but not by lanthanum (100 microM). Furthermore, single-cell reverse transcription-PCR analysis revealed that TRPC1, TRPC3, TRPC4, TRPC5, TRPC6, and TRPC7 subunits were expressed in GnRH neurons. Therefore, it appears that kisspeptin depolarizes GnRH neurons through activating TRPC-like channels and, to a lesser extent, inhibition of Kir channels. These actions of kisspeptin contribute to the pronounced excitation of GnRH neurons that is critical for mammalian reproduction.
authors.affiliation: Department of Physiology and Pharmacology, Oregon National Primate Research Center, Oregon Health & Science University, Portland, Oregon 97239-3089, USA.
authors.forename: Chunguang
authors.initials: C
authors.lastname: Zhang
authors.forename: Troy A
authors.initials: TA
authors.lastname: Roepke
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Kelly
authors.forename: Oline K
authors.initials: OK
authors.lastname: Rønnekleiv
mesh_terms: D000818:Animals; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism* / Q000502:physiology; D059648:Kisspeptins; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000378:metabolism* / Q000502:physiology; D050052:TRPC Cation Channels / Q000819:agonists* / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000502:physiology*
chemical_list: C106628:KISS1 protein, human; D059648:Kisspeptins; D050052:TRPC Cation Channels; D025521:Tumor Suppressor Proteins; D007987:Gonadotropin-Releasing Hormone