AB319. SPR-46 In vivo hypogastric nerve electrical stimulation contracts the canine detrusor

Objective: Our goal was to determine whether electrical stimulation of the hypogastric nerve in dogs with intact bladder innervation results in contraction of the detrusor muscle of the bladder. The effects of the anesthetics isoflurane versus propofol on detrusor pressure with hypogastric nerve stimulation were compared.

Methods: A total of 14 female mixed-breed hounds with intact bladder innervation, body mass of 20–25 kg and 6–8 months of age were used. Maximum changes in detrusor pressures were determined following electrical stimulation (3–10 mA, 20 Hz) of the hypogastric nerves under isoflurane inhalation anesthesia at 1–3% mean alveolar concentration in oxygen (n=14). Five of these same dogs were then transitioned to propofol anesthesia administered intravenously by continuous-rate infusion (0.3–0.5 mg/kg/min). Detrusor pressures were recorded at a sampling rate of 4/s using PowerLab software (AD Instruments) and displayed using LabChart. Following electrical stimulation, hypogastric nerves were harvested from five dogs undergoing decentralization for other experiments. These nerves were cryosectioned and examined for expression of the adrenergic marker enzyme tyrosine hydroxylase (present in sympathetic peripheral nerves) using immunohistochemical methods.

Results: Electrical stimulation of the hypogastric nerve caused an increase in detrusor pressure (2 to 9 cmH₂O) under isoflurane anesthesia in 11 of 14 dogs. Two of the 5 dogs tested under propofol anesthesia showed an increase in detrusor pressure after switching from isoflurane to propofol, another showed no change, and the remaining two showed an absence of bladder contractions in response to hypogastric nerve stimulation under either anesthetic. Each collected hypogastric nerve showed positive tyrosine hydroxylase immunostaining, confirming that the nerves contain sympathetic fibers.

Conclusions: These results indicate that the neuronally intact canine detrusor muscle contracts during hypogastric nerve stimulation under both isoflurane and propofol anesthesia. These results confirm findings by de Groat and colleagues in cats and by Elmer in rats showing that electrical stimulation of hypogastric nerves in animals with intact bladder innervation elicits low-amplitude bladder contractions.

Funding Source(s): NIH-NINDS NS070267

Keywords: Neuromodulation; hypogastric nerve; dog; bladder; immunostaining