Abstract
Barrington's nucleus, or pontine micturition center, has been shown to project directly to the sacral area using neuron tracing technique: the area involves preganglionic neurons (PGN) that innervate the bladder muscle. We examined using electrophysiological technique whether this nucleus connects directly to sacral PGNs, and whether the efferent inputs from this nucleus are modulated by micturition cycle, i.e., voiding phase and relaxation phase, in cats anesthetized with α-chloralose. 1. Intracellular recordings were made from sacral PGNs that were identified by antidromic activation from the sacral ventral root. Single to three electrical shocks to Barrington's nucleus (up to 100 μA, 200Hz) evoked weak or no excitatory postsynaptic potentials (EPSPs) in PGNs during relaxation phase. On the other hand, clear EPSPs with latencies of 9-48 ms were evoked during voiding phase. Latencies of EPSPs were not fixed in any PGNs, indicating that EPSPs were evoked polysynaptically. 2. Stimulous effects of Barrington's nucleus on bladder contraction were examined. Stimulation was much more effective during voiding phase: a few train pulses were enough to evoke further bladder contraction. While during relaxation phase, 30-50 train stimulation was needed to evoke bladder contraction. The observations suggest that there is no direct connection between Barrington's nucleus and sacral PGNs, and that this descending pathway to sacral PGNs is facilitated during voiding cycle. [J Physiol Sci. 2007;57 Suppl:S240]
