The gold standard for interpretation of slow wave frequency in in vitro and in vivo recordings by extracellular electrodes

Abstract

The slow wave in gastric and intestinal smooth muscle is a periodic depolarization that sets up electrical conditions for smooth muscle cells to contract in response to the release of acetylcholine from the myenteric excitatory motor neurons. Accordingly, the smooth muscle cells contract only once during a slow wave. Therefore, the maximum frequency of contractions at a given location in the gastrointestinal tract cannot exceed the frequency of slow wave at that location. Alvarez and colleagues (Alvarez & Mahoney, 1922; Berkson et al. 1932), using extracellular electrodes, were the first to identify the slow wave in the canine stomach and small intestine and noted a one-to-one relationship between slow wave and contraction when the muscles were active. Since then, many investigators have validated the recording of slow wave s by extracellular electrodes and their relationship to the maximum contraction frequency in the gastrointestinal tract of humans and experimental animals. Starting in the sixties, intracellular recordings from smooth muscle cells confirmed slow waves in these cells (Daniel, 1966; el-Sharkawy et al. 1978). Since then the recording of slow waves by extracellular and intracellular electrodes has served as an important tool to understand gut motility function in health and disease.