Localization of olfactory cyclic nucleotide-gated channels in rat gonadotropin-releasing hormone neurons

The GT1 GnRH cell Lines express all three subunits of the cyclic nucleotide-gated (CNG) channels (CNG2,4.3 and 5) expressed in olfactory neurons. We investigated using in situ hybridization and double immunofluorescence whether endogenous GnRH neurons in the rat also express CNG channel subunits. Sections from male and female adult rats were hybridized with a digoxigenin-labeled riboprobe made to regions of rat GnRH CNG2, CNG4.3 or CNG5 cDNAs. In both sexes, 70-80%. of GnRH neurons contained mRNAs for CNG2, CNG43 and CNG5. Similarly, double immunofluorescence staining for GnRH and CNG-2, CNG4.3 or CNG5 confirmed that 70-80% of GnRH perikarya contained all three CNG subunit proteins. Moreover. die distribution of the immunostaining of CNG subunits in the extemal layer of the median eminence overlapped with GnRH staining. These findings demonstrate that endogenous GnRH neurons, like GT1 cells, express all three subunits necessary to form cANP-gated cation channels, findings consistent with the presence of functional cANP-gated cation channels. The presence of CNG channel subunits in the median eminence supports the notion that coordination of the excitability of the scattered GnRH perikarya my occur at the level of the nerve terminals.