Spontaneous electromechanical activity in the rat duodenumin vitro

Abstract

Isolated rat duodenum shows spontaneous mechanical and electrical activities. Mechanical activity consists in changes both in endoluminal pressure and in isometric tension. Electrical activity is characterized by slow waves with superimposed bursts. This spontaneous activity is tetrodotoxin (TTX) resistant and therefore it is myogenic in origin. Indeed, TTX pretreatment, even in the presence of atropine and guanethidine, caused an increase in amplitude and in frequency of the electrical and mechanical activities. This finding indicates the presence of tonically active inhibitory intramural non adrenergic, non cholinergic (NANC) nerves. Duodenal longitudinal strips showed a spontaneous mechanical activity resembling that one recorded from isolated segment. Instead, circular strips are quiescent under resting condition and a contractile activity can be detected only after TTX pretreatment suggesting that: i) the circular smooth muscle layer is tonically inhibited by intramural NANC nerves and, ii) the contractions observed in the rat duodenum are due to the activity of the longitudinal one.

A comparison of the organization of longitudinal and circular contractions during pendular and segmental activity in the duodenum of the rat and guinea pig

“…Our results regarding the rate of occurrence of longitudinal contractions in the duodenum of the rat do not allow such distinction. The frequency of the fast phasic longitudinal contractions obtained in our study was close to that previously reported in an ex vivo manometric study of a 2 cm length of rat duodenum (33.4 ± 1.62 cpm) and to the slow wave frequency in the same preparation (34.2 ± 4.4 cpm) 24 . It was also similar to that in the rat (27 cpm), 36 which was reported to be unmodified following addition of tetrodotoxin.…”

“…Later work showed that segmentation could involve both circular and longitudinal musculature 14 and was induced by nutrients such as decanoic acid 8 . Moreover, it was postulated that segmental contractions are regulated by elements of the enteric nervous system (ENS) 12,22–25 . Work also showed that segmental contractions may be progenitors of peristaltic contraction as some may propagate a short distance along the duodenum while others could propagate for longer distances 8 .…”

Imatinib Blocks Spontaneous Mechanical Activities in the Adult Mouse Small Intestine: Possible Inhibition of c-Kit Signaling

“…The contractions consisted of homogeneous waves. Consistent with previous reports [4,16,17] , we confi rmed that tetrodotoxin (0.1 mol/l) did not abolish spontaneous rhythmic contractions, suggesting the basal mechanical activities were not neuronal in origin (data not shown).…”

Interplay between myogenic pacemakers and enteric neurons determine distinct motor patterns in the rat colon

“…Waxing and waning of slow waves in intestinal musculature results in high (wax) and low (wane) open probability for Ca 2+ channels, and has been previously recorded in other areas of the gastrointestinal tract and species such as the cat small intestine, the porcine ileum, the rat duodenum or the human colon . Diamant and Bortoff already in 1969 suggested that the wax and wane phenomenon could be possibly attributed to the interaction of two competing pacemakers, but they believed these pacemakers were both the slow wave generating pacemakers.…”