Effect of procaine and oxethazaine on muscarinic receptors of parietal cells.

: Several reports have shown that local anesthetics have a high affinity for muscarinic receptors and competitively inhibit the effects induced by cholinergic agents in various tissues, but there have been no reports on the muscarinic receptors of parietal cells. The effects of five doses of procaine (10(-8)M approximately 10(-4)M) and seven doses of oxethazaine (10(-8)M approximately 10(-5)M) on 14C-aminopyrine accumulation in isolated parietal cells of guinea pigs induced by 10(-4)M carbachol were studied. Procaine showed a potentiating effect with peak potentiation at a dose of 10(-5)M, while oxethazaine showed an inhibitory effect in a dose-dependent manner at doses higher than 3 x 10(-8)M and suppression below the control levels at doses higher than 3.5 x 10(-7)M. Procaine alone increased 14C-aminopyrine accumulation with peak response at a dose of 10(-5)M, while oxethazaine alone showed an inhibitory effect in a dose-dependent manner at doses higher than 3 x 10(-8)M. Oxethazaine shifted the carbachol dose-response curves to the right with suppression of maximal response. In conclusion, in parietal cells, procaine appears to display roughly similar action to carbachol through muscarinic receptors, while oxethazaine displays inhibitory action mainly by mechanisms other than inhibition at the muscarinic receptor site.