Rat GnRH Neurons Exhibit Large Conductance Voltage- and Ca²⁺-Activated K⁺ (BK) Currents and Express BK Channel mRNAs

Abstract

Gonadotropin-releasing hormone (GnRH) neurons form the final common pathway for the central regulation of reproduction. Like in other neurons, the discharge pattern of action potentials is important for GnRH neurons to function properly. Therefore, it is important to elucidate the expression patterns of various types of ion channel in these neurons, as these determine cell excitability. To date, voltage-gated Ca²⁺ channels and SK channels have been reported to be expressed in rat GnRH neurons. In this study, we focused on K⁺ channels and analyzed their expression in primary cultured GnRH neurons, prepared from GnRH-EGFP transgenic rats, by means of perforated patch clamp recording. GnRH neurons exhibited a delayed-rectifier K⁺ currents and large conductance voltage- and Ca²⁺-activated K⁺ (BK) currents. Moreover, multi-cell RT-PCR experiments revealed the expression of BK channel mRNAs (α, β1, β2, and β4). The results show the presence of delayed-rectifier K⁺ currents and BK currents in addition to previously reported slow afterhyperpolarization currents. These currents control the action potential repolarization and probably also the firing pattern, thereby regulating the cell excitability of GnRH neurons.