THE INTERACTION OF HISTAMIN AND NICOTINE ON THE INTESTINE

The action of nicotine on the intestine has been the subject of a great deal of work and the exact mechanism of its action is not yet entirely clear. That it does not act directly on the muscle is indicated by the work of Magnus (1) who showed that plexus-free intestinal strips of the cat did not react to nicotine, and by Rydin (2) who showed that rabbit intestine inhibited by nicotine still reacted to barium. The latter also showed along with a number of other workers that the action of piocarpine and acetyl-choline was inhibited by nicotine. This seems to show definitely that nicotine must act on the vagus endings. On the other hand Ikeda (3) believes that inhibition of rabbits ’ intestine by nico-tine is due to the stimulation of sympathetic ganglia. The whole subject is further complicated by the fact that nicotine causes a marked contraction of the intestine before inhibition. This con-traction is of short duration and may be due to stimulation of sympathetic or vagus endings or according to Ikeda to stimula-tion of smooth muscle directly. It has been shown (4) that there is a quantitative antagonism between histamin and atropin on guinea pig intestine. It was therefore of interest to see whether a similar relationship held between nicotine and histamin. This was found to be the case although the concentration of nicotine necessary to produce re-laxation after contraction by histamin was much greater than that of atropine