Interaction of the postsynaptic effects of glycine and GABA on spinal cord neurons in the frog Rana temporaria.

Studies were performed on mechanically isolated spinal cord multipolar cells (presumptive motoneurons) from the frog Rana temporaria using patch-clamp methods in the whole-cell configuration. These experiments showed that the amplitudes of transmembrane currents arising in response to simultaneous application of GABA and glycine were smaller than the sums of the amplitudes of the responses of the same neurons to GABA and glycine applied individually. Investigation of the mechanisms of this occlusion showed that superfusion of neurons with glycine solution (0.2 mM) resulted in complete blockade of responses to application of GABA (5 mM) and vice versa. This phenomenon may have resulted from cross-blockade associated with the existence of a single receptor complex sensitive to both GABA and glycine and from the interaction of GABA and glycine receptors.