Nervous Control of Urinary Bladder in Cats: II. The expulsion phase

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Abstract
Edvardsen, P. Nervous control of urinary bladder in, cats. II. The expulsion phase. Acta physiol. scand. 1968. 72. 172–182.The volume threshold for micturition is altered by transection of the brain stem at variousu levels and also by section of the sympathetic nerves to the bladder. The aim of the present experiments has been to investigate whether the supraspinal influences are brought about by means of changes in peripheral sympathetic mechanisms. Mostly male cats were investigated using the ‘direct cystometry’ method. Cystometrograms obtained preoperatively were compared with those obtained after peripheral sympathectomy and during the phase of increased motility following laparotomy. Then the effects of brain stem transection on the micturition threshold in the. presence and absence of sympathetic innervation were compared. The peripheral factor responsible for eliciting the micturition reflex was found to be the tension in the bladder wall as assessed from the intravesical pressure. The lower volume threshold found after sympathectomy is due to the hypertonicity of the bladder following this procedure. The tonic supraspinal influence on the micturition reflex, on the other hand, was not altered by interruption of the sympathetic nerve supply to the bladder. Thus, the expulsion of urine is controlled by two different mechanisms, namely a peripheral regulation of the tension in the bladder wall and a supraspinal regulation of the micturition reflex threshold.