Spontaneous electrical activity was recorded with bipolar electrodes from the gastrointestinal tracts of unanesthetized fasted cats (upper and lower cut-off frequencies: 35 and 3 Hz). In addition to slow waves (SWs) and spike potentials (SPs), the following three patterns of activity were recorded that are not observed in vitro. 1) Intense bursts of SPs (migrating spike complexes, MSCs) migrate caudally at a velocity of approximately 1 mm/s. MSCs resemble migrating myoelectric complexes (MMCs) in their velocity and by their traversal of intestinal anastomoses. SWs are usually suppressed during and immediately after the MSC, and, on their return, propagate at a higher velocity than they do prior to the MSC. Unlike its effect on MMCs, motilin does not appear to elicit MSCs, a finding consistent with the fact that MSCs occur infrequently in the duodenum and not at all in the antrum. 2) Bursts of SPs are found in the absence of recorded SWs. The SP bursts are of variable duration and occur virtually simultaneously at several recording sites, or propagate at 1-2 cm/s in either direction along the jejunum. The more usual caudally propagating SPs occur when SWs reappear. 3) "Minute rhythms," periods of spiking SWs, occur simultaneously over long lengths of upper bowel, sometimes including antrum, at intervals of about 1-2 min. It is proposed that, despite their differences, the cat MSC may be the functional counterpart of the MMC, that cat SWs are not omnipresent, and that the minute rhythms described here are of central origin.
Spontaneous Electrical Activity and Rhythmicity in Gastrointestinal Smooth Muscles
