Effect of nicotine on the pelvic afferent nerve activity and bladder pressure in rats.

OBJECTIVES: To record afferent nerve activity and bladder pressure in anesthetized male rats and to investigate whether increased afferent nerve activity induced by nicotine is able to evoke reflex bladder contractions.
METHODS: Using continuous infusion cystometrography, bladder pressure was measured via a bladder cannula. Afferent activity was recorded in the uncut L6 dorsal root. Nicotine was injected intra-arterially through a cannula placed near the bifurcation of the internal iliac artery a few minutes after micturition.
RESULTS: Nicotine (0.15-1.5 micromol) evoked a marked elevation of afferent discharge without a simultaneous increase in bladder pressure. Bladder contractions appeared about 43 and 19 s after bolus injection of nicotine at 0.45 and 1.5 micromol, respectively. Firing rates of afferent nerves were reduced when the contraction appeared. Continuous infusion of nicotine at 0.75 micromol/min for 20 min evoked marked elevation of afferent discharge, which was maintained during infusion of nicotine and after it had been withdrawn. Repetitive contractions were observed thereafter and disappeared when the L6 dorsal roots were bilaterally resected.
CONCLUSIONS: A transient increase in afferent discharges induced by bolus injection of nicotine was unable to evoke reflex bladder contraction. Repetitive bladder contractions after withdrawal of continuous nicotine infusion were induced in a reflex manner by the increased afferent activity.