Synaptogenesis in Co-Culture of Neurons of Dorsal Root Ganglia and Spinal Cord

In co-culture of spinal cord and dorsal root ganglion (DRG) neurons, we studied at different terms of culturing postsynaptic currents in DRG neurons evoked by direct electrical stimulation of single spinal neurons using a voltage-clamp technique in the whole-cell configuration. According to the reversal potential and sensitivity to bicuculline, these currents were classified as inhibitory postsynaptic currents (IPSC) carried by Cl^- ions through GABA_A receptors. During neuronal development in dissociated co-culture, the amplitude of evoked IPSC and their time to peak significantly increased. The time to peak of spontaneous IPSC (sIPSC) in DRG neurons remained unchanged, while the frequency of these currents increased with increasing culturing time. It is concluded that under culturing conditions spinal neurons establish inhibitory synaptic contacts with the somata of DRG neurons, and the number of such functional contacts increases in the course of culturing. Our findings show that in dissociated co-culture the process of formation of inhibitory synapses on the axon terminals of primary afferent neurons is akin to that realized in vivo, but with dissimilar topography of distribution of such synapses.