The effects of chronic ganglion blockade and chronic cholinesterase inhibition on the sensitivity of rabbit stomach muscularis to cholinergic and adrenergic agonists.

The EC50 values, KA values and efficacies (e) of selected agonists have been determined in strips of stomach muscularis from control, chlorisondamine-pretreated and O, O-diethyl S[2(ethylthio)ethyl]phosphodithioate (disulfoton)-pretreated rabbits. Strips from chlorisondamine-pretreated animals were supersensitive to carbachol but normosensitive to phenylephrine; the e but the KA of carbachol was affected by this treatment. The KB of atropine was unchanged. Strips from animals treated with disulfoton were subsensitive to phenylephrine but normosensitive to amidephrine and carbachol; both the e and KA of phenylephrine appeared to be elevated by this pretreatment. The KB of phentolamine remained unchanged. These results indicate that the chlorisondamine-induced supersensitivity is the result of a change beyond the level of the cholinergic receptors. In contradistinction, the subsensitivity to phenylephrine after disulfoton pretreatment may result at least in part, from a qualitative change in the alpha adrenergic receptors in the stomach muscularis.