Inhibiting effects of morphine, chloroquine, nonsteroidal and steroidal anti-inflammatory drugs on electrically-induced contractions of guinea-pig ileum and the reversing effect of prostaglandins.

Twelve different non steroidal antiinflammatory drugs (NSAID), five steroidal antinflammatory drugs, morphine and chloroquine have been added at various concentrations to in vitro electrically-stimulated preparations of guinea-pig ileum. They all inhibit the electrically-induced contractions. Prostaglandins E as well as nicotine reverse this inhibition. These reversing effects are less evident on totally inhibiting drug concentrations than on partially inhibiting drug concentrations. It is suggested that this inhibiting effect could be due mostly to nervous as well as muscular membrane permeability changes induced by these drugs and not to inhibition of prostaglandin synthesis which could be only proposed as partial explanation for NSAID effects. The reversing action of nicotine could be related to a release of acetylcholine while a sensitization of guinea-pig ileum smooth muscle to acetylcholine could explain the reversing properties of prostaglandins.