α-Chloralose alters autonomic reflex function of the lower urinary tract

The effects of α-chloralose on the micturition reflex were evaluated using an efficiently voiding decerebrate cat model. At laparotomy cannulas were introduced into the urethra and/or bladder for measurement of urethral perfusion pressure and/or bladder pressure during bladder filling and voiding. After establishment of efficient voiding in the anesthetic-free decerebrate cat, chloralose, 50 mg/kg iv, was administered. Parameters assessed before and after anesthetic included bladder pressure at peak of contraction (voiding pressure), intravesical pressure at onset of bladder contraction (threshold pressure), contraction amplitude, duration of bladder contraction, bladder volume at onset of bladder contraction (volume threshold), and residual bladder volume after voiding (postvoid residual). In addition to these parameters, preparations with intact bladder-urethra and with divided bladder-urethra were used to assess effects of chloralose on voiding efficiency and coordination between bladder and urethra, respectively. Chloralose significantly reduced voiding pressure, contraction amplitude, and voiding efficiency. Neither vehicle for the chloralose nor sympathetic denervation of the lower urinary tract affected these reductions. Chloralose had no effect on direct contraction of the bladder and urethra produced by intra-arterial acetylcholine (25-100 μg). Chloralose converted the synergic bladder and urethral responses during voiding to dyssynergic responses. Neuromuscular blockade with gallamine, 10 mg/kg iv, improved voiding efficiency. It is concluded that the adverse effect of chloralose on the reflex function and coordination of the lower urinary tract is primarily due to an effect on the reflex pathways mediating bladder contraction. A secondary adverse effect is on pathways, possibly somatic, mediating vesicourethral coordination.