The overall objectives of this project continue to be the elucidation of mechanisms which serve to coordinate visceral smooth muscle activity. During the next granting period our efforts will be directed toward: a) Studying the effects of estrogen, progesterone and 17-OH-progesterone on the electrical activity, intercellular electrical coupling and mechanical properties of gastrointestinal muscle, both in chronic animal preparations and in vitro. b) Studying the alterations of slow wave activity in the small intestine of the cat produced by the migrating myoelectric complex. c) Studying the changes in electrical and mechanical activity accompanying hypertrophy of intestinal muscle associated with pressure overload caused by chronic obstruction, or volume overload caused by extensive intestinal resection, especally of the upper small intestine. These studies will involve chronic dog and cat preparations, isolated smooth muscle preparations and microelectrode recording.