Non-Neurogenic Basis of Bladder Tonus

Abstract

Effects of lesions at various levels of the neural axis on bladder tonus and the micturition reflex in 55 cats were compared. Bladder tonus was defined as that property of the bladder reflected in the slope of the vesical pressure-volume curve on the cystometrogram. The threshold excitability of the micturition reflex was measured as the volume just sufficient to elicit micturition. Micturition reflex excitability was greatly increased by intercollicular decerebra-tion and moderately so by supracollicular decerebration. It was greatly reduced following conversion of a transhypothalamic decerebrate to a supracollicular decerebrate preparation, and greatly increased following conversion of a supracollicular to an intercollicular decerebrate state. Bladder tonus was not affected by any of these conversions. Subcollicular decerebration or spinal transection completely abolished the micturition reflex, but did not affect bladder tonus. These results indicate that bladder tonus is not subject to supraspinal nervous influences. Bilateral sacral rhizotomy in spinal animals did not affect bladder tonus indicating that it is not mediated by a spinal reflex. The ganglionic blocking agent tetra-ethyl ammonium chloride (50 mg/kg body weight, intramuscular) failed to alter bladder tonus in spinal preparations indicating that bladder tonus is not mediated by a peripheral ganglionic reflex. Ether and Nembutal in dosages sufficient to abolish the micturition reflex did not affect bladder tonus. Even 10-20 minutes after the death of an animal, the tonus remained the same as it had been in the intact animal. The results indicate that the influence of the nervous system on the bladder is solely for the control of the micturition reflex and not for the control of tonus. Stretch or distention was the only factor found to influence bladder tonus. Bladder tonus changed progressively following repetitive cystometric determinations. It was concluded that bladder tonus is non-neural in nature, reflecting the physical state of the bladder wall.