Ionic Conductances in Dissociated Smooth Muscle Cells

Abstract

Conclusion

Gastrointestinal and vascular smooth muscle cells appear to possess similar ion channels in their membranes but differ in how some of these channels are modulated. This, however, is not surprising since they react in a different manner physiologically to autonomic neurotransmitters such as acetylcholine and norepinephrine. Smooth muscle constrictors, norepinephrine in the case of vascular muscle, and acetylcholine in the case of gastrointestinal muscle, appear to share the common property of activating Ca²⁺ channels. However, whether these agents affect the Ca²⁺ channels directly or through second messenger systems remain to be determined. Vasodilators, on the other hand, appear to work via activation of K⁺ channels, specifically, the ATP-sensitive K⁺ channel. The ionic mechanism responsible for norepinephrine's decrease in the motility of gastrointestinal smooth muscle cells remains unknown at the present time.

Thus, a wealth of information has been gathered within the past several years concerning the ionic channels that are present in various types of dissociated smooth muscle cells utilizing the patch-clamp technique. However, a lot of important questions still remain unanswered and will no doubt be an area of fruitful research for the foreseeable future. Another challenge that needs to be addressed in the future would be to apply the knowledge learned from these isolated cells to account for the observations seen in intact tissue.