Progesterone and Allopregnanolone Enhance the Miniature Synaptic Release of Glycine in the Rat Hypoglossal Nucleus

The study explored the effects of progesterone and its metabolite allopregnanolone on glycinergic neurotransmission in rat hypoglossal motoneurons. Using whole-cell patch-clamp techniques, researchers found that a 20-minute superfusion with progesterone increased the frequency of glycinergic miniature currents. This effect was not observed when 5α-reductase was blocked, indicating that the effect of progesterone is likely due to its conversion to allopregnanolone. Allopregnanolone itself also increased glycine release, while epiallopregnanolone did not. The study suggested that these effects might be due to the potentiation of presynaptic GABA receptor channels, which could reduce neuronal excitability and offer neuroprotection against excitotoxicity.