A spinal cord slice preparation for analyzing synaptic responses to stimulation of pelvic and pudendal nerves in mature rats

Abstract

The dorsal commissural nucleus (DCN) in the lumbosacral spinal cord (L6–S1) receives primary afferent fibers from both pelvic and pudendal nerves in rats. However, the physiological and pharmacological properties of synaptic responses of the DCN neurons to stimulation of those nerves remain unclear. We have developed a longitudinal spinal cord (L6–S1) slice preparation from mature rats that retained both nerves attached. Blind whole-cell recordings were made from the DCN neurons in this preparation. In most neurons, mono- and/or poly-synaptic fast excitatory postsynaptic potentials (EPSPs) were evoked by electrical stimulation of either the pelvic or pudendal nerve. These EPSPs were mediated by activation of Aβ/Aδ and/or C fibers (conduction velocities, 0.5–17.3 m/s), and were abolished by CNQX. Fast EPSPs elicited by either pelvic or pudendal nerve stimulation were occasionally accompanied by bicuculline- and strychnine-sensitive IPSPs. In one-third of the neurons tested, mono- and/or poly-synaptic EPSPs were elicited by the stimulation of both the pelvic and pudendal nerves, indicating convergence of the visceral and somatic primary afferent inputs from the pelvic region onto the DCN neurons. The preparation is applicable to study the mechanism of the integration of the visceral and somatic inputs in the spinal cord.