Genistein Excitation of Gonadotrophin-Releasing Hormone Neurones in Juvenile Female Mice

We investigated the effects of the phytoestrogen genistein on gonadotrophin-releasing hormone (GnRH) neurones using single-cell electrophysiology on GnRH-green fluorescent protein (GFP) transgenic juvenile female mice. Perforated patch-clamp recordings from GnRH-GFP neurones showed that approximately 83% of GnRH neurones responded to 30 μm genistein with a markedly prolonged membrane depolarisation. This effect not only persisted in the presence of tetrodotoxin, but also in the presence of amino acid receptor antagonists, indicating the direct site of action on postsynaptic GnRH neurones. Using a voltage clamp technique, we found that 30 μm genistein increased the frequency of synaptic current of GnRH neurones clamped at -60 mV in the presence of glutamate receptor blocker but not GABA_A receptor blocker. Pre-incubation of GnRH neurones with 30 μm genistein enhanced kisspeptin-induced membrane depolarisation and firing. GnRH neurones of juvenile mice injected with genistein in vivo showed an enhanced kisspeptin response compared to vehicle-injected controls. The transient receptor potential channel (TRPC) blocker 2-aminoethoxydiphenyl borate (75 μm) blocked the genistein-mediated response on GnRH neurones. These results demonstrate that genistein acts on GnRH neurones in juvenile female mice to induce excitation via GABA neurotransmission and TRPCs to enhance kisspeptin-induced activation.