The study of neurotransmission at the level of individual synaptic connections in the central nervous system of highly organized vertebrates is associated with considerable methodological and conceptual challenges. These include the large diversity of neuronal elements and the involvement of numerous modulatory systems within complex neural networks. Therefore, the analysis of synaptic transmission and its plastic properties is most appropriately performed using simplified neuronal networks, particularly co-cultures of pre- and postsynaptic neurons. Certain model systems, such as the dissociated co-culture of dorsal root ganglion (DRG) neurons and dorsal horn (DH) neurons of the rat spinal cord, are capable of reproducing in vivo features of the first functional relay of somatosensory information transfer from the periphery to the CNS. Such model systems represent a valuable tool for experimental analysis of interneuronal interactions, modulation of neurotransmission, and synaptic plasticity. In this article, we present the methodology and advantages of using DRG–DH co-culture in electrophysiological experiments to investigate synaptic transmission in primary somatosensory synapses.