A dual mechanism for intestinal motor effects of methyl methacrylate vapor

The influence of methyl methacrylate (MMA) vapor on the motor activity of the isolated guinea pig ileum is summarized in this report. MMA vapor was delivered to innervated and denervated strips via the tissue bath air supply at a concentration of 755 +/- 38 ppm. Innervated strips usually showed spontaneous motor activities (sma) which developed shortly after the muscle was mounted. None of the denervated strips exhibited sma. Upon exposure to MMA vapor, there was a rapid and significant decrease in sma and in the contractile responses to electric field stimulation and 0.01 mg acetylcholine administration. Denervated strips demonstrated a similar reduction in response magnitude to electric field and drug stimulation but required a longer time period. The persistence of the MMA-induced inhibitory response of the denervated strips indicates that the inhibitory effect is partly due to a direct action of the agent upon the contractile mechanism of the small intestine.