Mechano-gated ion channels provide a mechanism for cells to respond directly to changes in their environment and are involved in several key cellular functions including cell division, regulation of volume, muscle tone and muscle.hypertrophy. Neurons, cardiac, and vascular smooth muscle cells have mechano-gated ion channels. However, the presence and significance of mechano-gated ion channels in gastrointestinal smooth muscle is unknown. The objective of this proposal is to establish the physiological importance of mechano-gated ion channels in single human and canine jejunal circular smooth muscle cells. The Preliminary data obtained by the PI suggest that membrane stretch, increase in cell volume, and cytoskeletal manipulation modulate the whole cell current in human and canine jejunal circular smooth muscle cells. Based on these preliminary data the working hypothesis of this proposal is that mechano-gated ion channels are present on smooth muscle cells and that activation of the channels results in changes in ionic flux and membrane potential, ultimately resulting in changes in intestinal contractility. There are three specific aims: (1) to determine if a change in shape or size of human and canine jejunal circular smooth muscle cells activates mechano-gated channels; (2) to determine which ion channel or channels underlies the increase in whole cell current evoked by a change in cell size or shape; and (3), to determine if regulation of mechano-gated ion channel open probability is dependent on the cellular cytoskeleton. The development of a dissociation technique for obtaining healthy human small intestinal smooth muscle cells by the PI will enable the use of patch clamp recordings and immunofluorescent techniques to address the three specific aims. The demonstration of mechano-gated ion channels in gastrointestinal smooth muscle will provide a novel pathway by which small intestinal smooth muscle cells can directly and appropriately respond to changes in their environment. Activation of mechano-gated ion channels may be of physiological significance in the smooth muscle response to changes in intraluminal pressure in normal digestion, and of pathophysiological significance in inflammatory or obstructive diseases such as Crohn's disease and strictures and in irritable bowel syndrome where mechano-gated ion channels may be overexpressed.