Journal of Neuroscience, Vol 13, 3090-3094, Copyright © 1993 by Society for Neuroscience
Membrane potential changes in sphincter motoneurons during micturition in the decerebrate cat
B Fedirchuk and SJ Shefchyk
Department of Medicine, University of Manitoba, Winnipeg, Canada.
Intracellular recordings from external urethral sphincter (EUS) and
external anal sphincter (EAS) motoneurons were obtained during micturition
in the decerebrate cat. The neural circuitry mediating micturition was
activated by distension of the bladder or by electrical stimulation of the
pontine micturition center (PMC). During micturition, the membrane
potential of EUS motoneurons hyperpolarized 3- 9 mV, during which time the
motoneuron somatic membrane conductance increased. The membrane
hyperpolarization could be reversed with passive diffusion or active
ejection of chloride from the intracellular microelectrode into the
motoneuron. In contrast, the membrane potential of EAS motoneurons either
depolarized slightly or showed no change during micturition. We have shown
that the neural circuitry mediating micturition can influence the EUS and
EAS independently. In addition, stimulation of the PMC provides a valuable
tool for identifying spinal neurons mediating the postsynaptic inhibition
of EUS motoneurons during micturition.