Urodynamic characteristics during animal hypnosis in the rabbit

Abstract

In animal experiments, in assessing the vesicourethral function, it is desirable to keep the micturition reflex in a physiologic state. Most anesthetics used to immobilize the animals tend to suppress the micturition reflex. An alternative means is decerebration. However, a decerebrate animal is not easily prepared. Instead of anesthesia or decerebration, we applied animal hypnosis to rabbits for immobilization. The urodynamic characteristics during animal hypnosis were compared with those under anesthesia. Twenty male rabbits weighting 2.5 to 3.0 kg were used. Animal hypnosis was produced by placing the rabbit on its back and restraining it in a V-shape trough and maintaining it there until it relaxed. Under hypnosis, cystometry was performed by the suprapubic route. The external sphincter EMG was recorded simultaneously with bladder pressure using a needle electrode. The urethral pressure profile was also measured during hypnosis. These measurements were repeated under anesthesia induced by intravenous pentobarbital injection (30 mg/kg). Furthermore, the hypnotic degree was assessed from respiratory rate and pupil size during these urodynamic measurements. In the rabbit, hypnosis began within 1 min and lasted for 30 to 60 min. During hypnosis, insertion of a catheter, pricking with a needle electrode and suprapubic puncture did not interrupt the immobility. Urodynamic study under animal hypnosis showed that, as bladder volume increased, the sphincter EMG. activity increased and that the EMG activity ceased with bladder contraction. Bladder contraction coincided with the expulsion of saline from the urethral meatus. The maximal bladder pressure during micturition was 23.5 ± 8.0 mmHg. The maximal bladder capacity at which the micturition reflex occurred was 41.4 ± 22.3 ml. EMG amplitude was 110 ± 49 μN. Pentobarbital reduced the amplitude of sphincter EMG to the value of 11.0 ± 8.0 μV. Furthermore, saline was infused into bladder passively from the urethral meatus. Thus, the micturition reflex did not occur under pentobarbital anesthesia. The urethral pressure profile could be measured during animal hypnosis. The maximal closure pressures were 87.6 ± 8.2 mmHg under hypnosis and 58.3 ± 2.36 mmHg under anesthesia. Thus, pentobarbital significantly depressed the pressure profile. Hypnosis was characterized by immobility, myosis and diminution of respiratory rate. These states were not changed during UDS. Compared with bladder and sphincter activity under pentobarbital, animal hypnosis was demonstrated to afford a more physiologic state. Therefore, this method seems to be useful for urodynamic studies in animal experiments. © 1990, THE JAPANESE UROLOGICAL ASSOCIATION. All rights reserved.