The Journal of comparative neurology
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Inhibitory synapses with large and gephyrin-rich postsynaptic receptor areas are likely indicative of higher synaptic strength. We investigated the presynaptic inhibitory neurotransmitter content (GABA, glycine, or both) and the presence and subunit composition of GABA(A) and glycine postsynaptic receptors in one example of gephyrin-rich synapses to determine neurochemical characteristics that could also contribute to enhance synaptic strength. Hence, we analyzed subunit receptor expression in gephyrin patches located on Renshaw cells, a type of spinal interneuron that receives powerful excitatory and inhibitory inputs and displays many large gephyrin patches on its surface. ⋯ Significantly, 40% of GABA(A) receptor clusters were opposed to presynaptic boutons that contained only glycinergic markers. We postulate that GABA and glycine corelease, and the presence of alpha3-containing GABA(A) receptors can enhance the postsynaptic current and contribute to strengthen inhibitory input on Renshaw cells. In addition, a certain degree of imprecision in the localization of postsynaptic GABA(A) receptors in regard to GABA release sites onto adult Renshaw cells was also found.