Abstract
Barrington's nucleus is a central component of the micturition circuit. Mainly two types of neurones have been identified: one type of neurones increases their firing during micturition contraction, and the other type decreases their firing during this phase (inverse neurones). The present study aims to elucidate a role of the inverse neurone in the regulation of the bladder contractility. [Methods] Single neurones in and around Barrington's nucleus were investigated with glass microelectrodes in anaesthetized cats. Projections of descending axons to the spinal cord were identified antidromically by stimulating the upper lumbar, mid lumbar, and/or lumbosacral levels. [Results] Inverse neurones displayed tonic firing when the bladder relaxes. The firing of most of the neurones began to decrease after the onset of micturition contraction. During micturition contraction, the majority of inverse neurones were completely silent, and the remaining neurones displayed weak tonic firing. When the bladder began to relax, firing rates increased again toward the previous steady level. But this firing increase occurred after the onset of the bladder relaxation. Most of the neurones were not activated antidromically from the spinal cord even when strong stimulus (more than 1 mA) was applied. In conclusion, the firing property (firing increase occurs after the onset of the bladder relaxation), as well as the scarceness of spinal cord-projecting neurones suggested that the inverse neurone in Barrington's nucleus does not trigger bladder relaxation. [Jpn J Physiol 54 Suppl:S197 (2004)]
