Propagation of individual spikes as "patches" of activation in isolated feline duodenum

Asynchrony of spikes has made it difficult to study the spatial and tempora l behavior of spikes in the gastrointestinal system. By simultaneously reco rding from a large number of closely spaced electrodes, we investigated the propagation of individual spikes. Recordings were performed from the seros al surface of the isolated feline duodenum at 240 sites simultaneously. Ana lysis of the tracings made it possible to reconstruct the propagation of in dividual spikes. Spikes propagate in the longitudinal and circumferential d irections in self-limiting areas or "patches." Conduction within patches ma y occur in the orad or aborad direction irrespective of the direction of th e slow wave. Most of the patches are smaller (<40 mm(2)), although inhomoge neous activation by the preceding slow wave may increase their size. Stimul ation by ACh, TTX, or tetraethylammonium does not affect the average patch size but does increase significantly their number and distribution in the d uodenum [from 26% (control) to 56%, 61%, and 72%, respectively]. In conclus ion, individual spikes activate limited areas or patches in the small intes tine, and pharmacological stimulation increases the number and distribution of these patches. In the small intestine, this pattern of activation would induce localized contractions. Contraction could be modulated by the size, number, and distribution of spike patches.