The action of neuropharmacologic agents on the bladder and urethra during experimental spinal shock

Pressure recordings within the bladder, proximal (U1) and middle (U2) thirds of the urethra have been monitored in anesthetized female mongrel dogs before and just after being made paraplegic, i.e., during the period of spinal shock. In the intact animal, parasympathetic stimulation produces uninhibited waves whereas U2 pressure remains unchanged; during spinal shock, it produces a small rise of intravesical pressure, without uninhibited waves but with a marked increase in U2 pressure. This may explain why bethanechol chloride is not effective in producing bladder emptying during spinal shock. Stimulation of the beta-receptors of the synpathetic nervous system and blockade of the alpha-receptors both singly and in combination produce urethral "sphincter" relaxation during spinal shock. This might allow bladder evacuation during spinal shock with the Credé maneuver or abdominal straining.