ABSTRACT
The smooth muscle of gastrointestinal tract undergoes almost continuous but slow electrical activity. This activity tends to have two basic types of electrical waves. Slow electrical waves are generated in the longitudinal muscle layer of small intestine and are not found in the circular muscle in the absence of longitudinal muscle. The other waves are peristaltic waves which are a reflex response. The purpose of the study was to deal with the mechanism of action involved in determining the therapeutic potential ofPGF2a and its antagonist in gastrointestinal motility. Rabbits of equal weights were brought from the animal house of BMSI and sacrificed in the Pharmacology Research laboratory. Ileum strips were isolated and with a special recommended methodology, longitudinal and circular muscles were separated. Individual muscle strips were then exposed separately to the desired drugs in the organ bath and readings were recorded on the polygraph machine. The study was performed at Basic Medical Sciences Institute, Jinnah Postgraduate Medical Center, Karachi from 1996 to 1998. PGF[2]alpha decreases the contractile effects of longitudinal muscles whether applied before or after the antagonist whereas in circular muscle it increases the amplitude of contraction. Indome-thacin antagonizes the effects of PGF[2]alpha in both longitudinal and circular muscle. Secondly when indomethacin applied directly it causes reduction in the amplitude of contraction in longitudinal muscle and increase in the force of contraction in circular muscle. Prostaglandin has a definite role on the smooth muscle ofileum; hence can be used in the regulation of intestinal motility. New drugs as an analogue or as an antagonist can be developed on the basis of these results