Effects of acupuncture to the sacral segment on the brainstem micturition center in rats

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Acupuncture to the sacral segment clinically improves urinary incontinence and increases bladder capacity in the patients of overactive bladder. To make clear this mechanism we examined effects of acupuncture to the sacral segment on the bladder activity and the neurons that are considered to be involved micturition. Experiments were performed in adult male rats under urethane anesthesia. Bladder pressure was recorded through a polyethylene catheter inserted from the dome into the urinary bladder, and saline was injected to the bladder from the catheter until it induced spontaneous contraction. Single neuronal activity was recorded through a glass pipette microelectrode in and around the Barrington's nucleus. The electrode was angled posteriorly by 30 ℃ and lowered through the cerebellum. We searched neurons that fired with relation to the bladder contraction. Three types of neurons were recorded. First was neuron almost silent during quiescent period and started to fire period to the bladder contraction. Second was those fired in close relation with bladder contraction. The third was those active during bladder relaxation and became inactive during contraction. When the neuronal activity accompanying spontaneous bladder contraction was recorded, acupuncture was applied. An acupuncture needle (stainless steel, outer diameter ; 0.3 mm) was positioned at the periosteum of sacral segment, and was rotated manually at a speed of about 3 turn/sec for 1 min.During the bladder contraction was suppressed by the acupuncture, activity of all three types of neurons was suppressed. These results suggest that the acupuncture produced suppression of activity of micturition center neurons, Which in turn caused suppression of bladder activity.