NEUROPHYSIOLOGICAL MODELING OF VOIDING IN RATS - BLADDER PRESSURE ANDPOSTGANGLIONIC BLADDER NERVE ACTIVITY

A model was developed that describes the relations between bladder pre ssure and both efferent and afferent nerve activity in postganglionic bladder nerves in urethan-anesthetized rats. Nerve activity was calcul ated as the 100-ms time integral of the rectified nerve signal. Affere nt and efferent nerve signals were measured separately by crushing the nerve proximally or distally. A linear relation was found between bla dder pressure and afferent nerve activity (fit error < 7%), and the re lation between bladder pressure and efferent nerve activity was descri bed by a low-pass filter (fit error < 9%). In most experiments, combin ed (efferent and afferent) nerve activity was measured. Absence of eff erent nerve activity was assumed during the pressure decrease immediat ely after voiding. From this episode, the afferent nerve activity was estimated for the entire measurement. Efferent nerve activity was then estimated assuming linear addition in the bidirectionally conducting nerves. The model described the measured data very well (fit error < 7 %), and the model parameters showed a good reproducibility in each rat (SD was similar to 30% of the mean).