Mechanisms of Interaction between GABA- and Glycine-Medicated Responses of Frog Spinal Cord Neurons

摘要

Whole-cell patch-clamp recordings were made from isolated frog (R. temporaria) spinal cord neurons to study the interaction between processes evoked by application of glycine and GABA. When GABA and glycine were applied simultaneously, neuron responses were always smaller than the sum of the responses to separate application of these neurotransmitters. The mechanisms underlying this occlusion phenomenon were identified. Firstly, GABA could activate glycine receptors (EC_(50) = 1.2 mM) in frog spinal cord neurons relatively effectively. Secondly, studies of the effects of application of glycine on the course of “rundown” of GABA-mediated responses showed that activation of glycine receptors facilitated inhibition of GABA_A receptors. Both of these mechanisms of interaction of neuron responses are presumptively mediated via simultaneous release of the neurotransmitters glycine and GABA in synapses.