AJP - Gastrointestinal and Liver Physiology, Vol 250, Issue 1 28-G34, Copyright © 1986 by American Physiological Society
Waxing and waning of slow waves in intestinal musculature
N. Suzuki, C. L. Prosser and W. DeVos
Electrical slow waves from cat or rabbit small intestine show more
variability when recorded in vivo than in vitro. One pattern of variation
is waxing and waning of amplitude, or "spindling," during which two rhythms
of slightly different frequency come in and out of phase. Fourier power
analyses of slow waves during spindles show two frequency peaks of slow
waves differing by 0.4-5.0 waves/min and corresponding to measured spindle
durations of 12-150 s. Spindles can be induced in vitro in rabbit intestine
by K depolarization of approximately 15 mV. Histograms of intracellular
recordings of slow nonspindling waves show variation of 0.5-1.0 s on either
side of a mean slow wave duration. Spindles are abolished by treatments
that reduce electrical coupling between cells, e.g., hypertonic sucrose or
lowered pH, but changes in calcium do not alter spindles. Simultaneous
recordings by two electrodes in the longitudinal axis show synchrony of
spindles at 2- to 3-mm but not at 5-mm separation and synchrony
circumferentially to the opposite side of a segment. Contractions, both in
vivo and in vitro, correspond with electrical spindles in amplitude.
Spindle durations were significantly shorter in vivo than in vitro,
indicating a significantly greater difference in vivo in the competing
frequencies at the point of recording (P less than 0.01). Three conditions
favoring waxing and waning are slight depolarization, variation in slow
wave frequency at a point, and electrotonic coupling between muscle fibers.
Spindles provide for rhythms of contractions of a 1- to 2-min period.
