In vivo electrophysiological recordings from spinal parasympathetic preganglionic neurons

Abstract

Parasympathetic preganglionic neurons in the lumbosacral spinal cord have an important role on the micturition reflex. We have developed in vivo patch-clamp and extracellular recording techniques to detect excitation of the parasympathetic preganglionic neurons in the lumbosacral spinal cord in combination with urinary bladder contraction monitoring, and examined neuronal firings and synaptic responses evoked in the preganglionic neurons during micturition. In vivo extracellular recordings from the lumbosacral parasympathetic nucleus showed that spontaneous firing was detected in vivo with characteristic bursts of firing coinciding with the increases in intravesical pressure during micturition. In vivo whole-cell recordings of membrane potentials of spinal parasympathetic preganglionic neurons under current-clamp conditions showed similar bursts of action potentials associated with the increased intravesical pressure. Excitatory synaptic currents having different kinetics were evoked under voltage-clamp conditions in single parasympathetic preganglionic neurons, suggesting that parasympathetic preganglionic neurons make synaptic contacts with different neuronal populations. In this review, we show neuronal mechanisms of spinal parasympathetic preganglionic neurons on micturition, and also describe principles of in vivo electrophysiological recording techniques.