Lack of effect of botulinum toxin on nonadrenergic, noncholinergic inhibitory responses of the guinea pig fundus in vitro.

The nonadrenergic, noncholinergic inhibitory (NAI) response of guinea pig fundic strip to electrical field stimulation was examined in the presence of botulinum toxin and tetrodotoxin. Tetrodotoxin completely abolished the NAI response while botulinum toxin did not alter it. It is concluded that the mediator of NAI responses is unlikely to be released with acetylcholine from cholinergic nerves or that such release would have to occur by a mechanism resistant to botulinum toxin.