PERTUSSIS TOXIN ATTENUATES PRESYNAPTIC INHIBITION OF CHOLINERGIC BUT NOT NONADRENERGIC NONCHOLINERGIC CONTRACTION IN GUINEA-PIG AIRWAYS

Several alpha-2- and opioid receptors exert their intracellular effect s via a pertussis toxin-sensitive G protein. Both cholinergic and nona drenergic noncholinergic nerve-mediated contractions of airways can be reduced by stimulation of presynaptic alpha-2- and opioid receptors. Using guinea pig trachea and bronchi, pretreated with pertussis toxin 100 mu g/kg or 0.9% NaCl, we investigated whether these inhibitory eff ects on airway contractions, evoked by electrical field stimulation, a re mediated via a pertussis toxin-sensitive G protein. The results ind icate a difference between cholinergic and excitatory nonadrenergic no ncholinergic neurotransmission. Inhibition of cholinergic contraction via presynaptic alpha-2- and opioid receptors seems to be mediated via a pertussis toxin-sensitive G protein, whereas inhibition of nonadren ergic noncholinergic contraction is not affected by pertussis toxin.