Effect of anesthetics on reflex micturition in the chronic cannula-implanted rat

It is well known that urethane is a suitable anesthetic for acute studies a nd has been extensively recommended for investigations related to micturiti on physiology. This is mainly because of the capability of urethane anesthe sia to spare reflex micturition as well as its easily established long-last ing and stable anesthetic level. However, urethane anes thesia is usually r estricted to acute experiments due to its potential toxicity. This study se arched for an alternative to urethane that would be suitable for studies in which recovery from anesthesia was needed. The list of administered drugs was as follows: pentobarbital, thiobutabarbital, ketamine-acepromazine, ket amine-diazepam, tiletamine-zolazepam, fentanyl-droperidol, alphaxalone-alph adolone, propofol, isoflurane, methoxyflurane, azaperone, tribromoethanol, and buprenorphine. Among these drugs, only tiletamine-zolazepam spared the reflex micturition contractions. However, the duration of this anesthesia w as too short (approximately 30 minutes) to complete the necessary testing a nd additional dosing of the anesthetic generally obliterated the micturitio n reflex. On the other hand, rats given i.v. urethane infusion (10% solutio n in 0.9% saline, 3.2-4.0 mg/kg/min, total dose 0.56-1.03 g/kg) maintained a stable anesthesia that permitted both reflex micturition and stereotaxic procedures. Rats moved spontaneously 3-16 hours after cessation of i.v. ure thane anesthesia and completely recovered in 2 days without significant aft er-effects. Bladder function was normal. No pathological changes were seen 1 week later. The present results suggest that urethane is the most suitabl e anesthetic for acute and chronic physiological experiments that require d emonstration of reflex micturition. (C) 2000 Wiley-Liss, Inc.