223 COMPARISON OF VARIOUS PARASYMPATHOMIMETICS FOR PRODUCTION OF CHOLINERGIC ATRIAL FIBRILLATION.

Application of acetylcholine (Miochol-E) and gentle rubbing of the atrial surface successfully induced atrial fibrillation (AF) in a number of species. In the 25-30 kg pig ( Sus scrofa domesticus ), episodes lasted 4 ± 1.3 min. We investigated the use of carbachol, Urecholine, and Prostigmin, chemicals with analogous structures or physiological roles, for their ability to generate similar episodes of AF at a concentration of 1:100. After exposing the atrium through a left thoracotomy and pericardiotomy, gentle trauma without pretreatment with a drug was unsuccessful in mechanically inducing AF. A control exposure with application of 0.25 cc acetylcholine produced AF lasting 5 minutes. A larger amount of carbachol (0.5 cc) had to be placed on the atrium in order to produce comparable episodes of AF. Both Urecholine and Prostigmin were ineffective in producing AF. To verify that the atrium was still capable of AF, another control with acetylcholine was performed, which again resulted in AF. We conclude that the use of carbachol at higher amounts in the pig induced episodes of AF equivalent to episodes produced by acetylcholine. In contrast, the drugs Urecholine and Prostigmin were not capable, in the concentration used, of provoking AF in this model.