Progesterone and allopregnanolone enhance the miniature synaptic release of glycine in the rat hypoglossal nucleus

The study investigated the effects of progesterone on glycinergic neurotransmission in rat hypoglossal motoneurons. It was found that a 20-minute superfusion with progesterone increased the frequency of glycinergic miniature currents, an effect that was not observed when 5α-reductase was blocked, indicating that the effect was due to progesterone's metabolism into allopregnanolone. Allopregnanolone itself also increased glycine release, while epiallopregnanolone did not. The study suggested that these effects were due to the potentiation of presynaptic GABA receptor channels, which could reduce neuronal excitability and protect against excitotoxicity.