Temporal and spatial rhythmicity of jejunal wall motion in rats.

Isolated segments of jejunum of fasted rats exhibit regular rhythmic contractions at the same frequency as slow-waves. The aim of the present study was to search for a possible spatial rhythmicity of this activity. Using a video imaging technique, jejunal segments of 50 rats were studied. Only experiments (n=76) with no propagated contractions at visual inspection were included in the study. After the measurement, a spectral analysis of the diameter variations was performed. The bands were characterized by four parameters: level, main frequency, amplitude and phase. At each level, the phase varied, suggesting that the same rhythmic phenomenon occurred, but with a delay as a function of the spatial position. In 58 measurements, the rhythmic activity had a frequency near 0.50 Hz and in 18, near 0.25 Hz. Phase difference was found in 32 segments (42%). The variation with distance was linear as a function of time and its length was greater for the low-frequency group than for the high-frequency group (25.6 +/- 9.4 vs. 33.3 +/- 5.2 mm, P=0.015). By contrast, the speed of propagation was not significantly different. The wavelength lambda of the spatial rhythmicity was 27.7 +/- 23.2 and 9.8 +/- 4.2 mm (P=NS) in the high- and low-frequency groups, respectively. This corresponds to a speed of propagation of v=lambda*f, where f is the frequency of the wall motion (7.0 +/- 5.2 vs. 5.2 +/- 2.2 mm sec-1, P=NS).