Inhibition of the bladder cooling reflex in the awake state: an experimental study in the cat.

Purpose: We assessed the bladder cooling reflex in the awake cat. The bladder cooling reflex is consistently observed in anesthetized adult cats but not in awake, neurologically normal humans. This discrepancy could indicate a state dependant control of the reflex or a species difference. This study was designed to differentiate between these alternatives,

Materials And Methods: Under ketamine-xylazine 5 animals had an indwelling catheter inserted into the bladder. The cooling reflex was tested by injections of cold saline into the bladder (4C to 8C), lowering its wall temperature to about 30C to 32C. The volume used (5 ml) was subthreshold for the Adelta micturition reflex, as confirmed by control injections of body warm saline. The procedure was repeated with the animals fully awake and it was well tolerated by all of them. Reflex responses were assessed by induced bladder pressures.

Results: Typical bladder cooling reflexes with peak pressures greater than 3 kPa were evoked in all cats when in narcotic sleep (group mean +/- CI 7.4 +/- 3.1 kPa). No such reflexes were elicited when the animals were awake (2.0 +/- 1.0 kPa). The difference was significant at the level of individual animals.

Conclusions: The bladder cooling reflex is suppressed in adult cats during wakefulness, as in humans. This state dependent control of the bladder cooling reflex adds to its resemblance to the extensor plantar response (Babinski's sign).