Profiling γ-Aminobutyric Acid (GABAA) Receptor Subunit mRNA Expression in Postnatal Gonadotropin-Releasing Hormone (GnRH) Neurons of the Male Mouse with Single Cell RT-PCR

Abstract

The present investigation has examined which subunits of the GABA_A receptor are expressed by gonadotropin-releasing hormone (GnRH) neurons in the juvenile and adult male mouse. Cells of defined morphology, located in the medial septum (MS) and rostral preoptic area (POA), were patch-clamped in the acute brain slice preparation and their cell contents extracted. A reverse transcriptase polymerase chain reaction (RT-PCR) procedure using nested primers was used to establish individual GnRH mRNA-expressing cells which were then evaluated for eleven GABA_A receptor (α1–5, β1–3, γ1–3) subunit transcripts. Single and multiple GABA_A receptor subunit mRNAs were detected in approximately 70% of all GnRH neurons. A range of different subunit mRNAs (α1, α2, α5, β1, β2, β3, γ2) were found in juvenile GnRH neurons, with the α1γ2 and α5γ2 combinations encountered most frequently within individual cells. The expression profile in adult GnRH neurons was more extensive than that detected in juveniles with α1, α2, α3, α5, β1, β2, β3, γ1 and γ2 subunits all being detected. The major difference in subunit profile between GnRH neurons located in the MS and POA involved the β subunits. The principal postnatal developmental change was one of increasing overall subunit heterogeneity in maturing POA GnRH neurons. The profile of GABA_A receptor subunit mRNAs detected in male GnRH neurons was quite different to that reported by us for female GnRH neurons in the mouse using the same RT-PCR approach. Together, these findings indicate that postnatal GnRH neurons are likely to express a range of GABA_A receptor subunit mRNAs in a sexually dimorphic and developmentally-regulated manner.