Atracurium and vecuronium block nicotine-induced carotid body chemoreceptor responses

Background: Vecuronium depresses carotid body chemosensitivity during hypoxia. We hypothesized that this is caused by inhibition of cholinergic transmission of the carotid body. Methods: The carotid body with its sinus nerve was removed en bloc from thiopentone-anaesthetized adult male New Zealand rabbits and perfused in vitro with modified Tyrodes buffer solution at constant perfusion pressure, temperature, a buffer pH of 7.4 and normocapnia. Chemoreceptor discharge and spike frequencies (fx) were recorded from the whole sinus nerve after administration of 500mug nicotine, given as duplicated controls and thereafter following 30 min perfusion of equipotent concentrations of atracurium (28.1 muM) or vecuronium(10 muM), after 30 min of neostigmine perfusion. (9.2 muM) and finally after 30min wash-out with buffer solution only. A short-lasting hypoxic test 0 was performed before and at the end of the experimental period to confirm the responsiveness and validity of the preparation. Results: Atracurium (n = 7) and vecuronium (n = 6) reduced chemoreceptor responses to nicotine by 70+/-30% and 66+/-19% (SEM) (P<0.05). Chemoreceptor discharges showed full recovery after neostigmine in the atracurium group and partial recovery in the vecuronium group (P<0.05). Finally, after wash-out the chemoreceptor responses to nicotine had fully recovered in both groups. Conclusion: Atracurium and vecuronium in equipotent concentrations block nicotine-induced chemoreceptor responses of the carotid body.