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

Background Little is known of the spatiotemporal organization of pendular duodenal contractions. Methods We used longitudinal and radial spatiotemporal mapping to examine and compare pendular and segmental contractile activity in the proximal duodenum of the rat and guinea pig when the lumen was perfused with saline or micellar decanoic acid. Key Results Isolated phasic longitudinal contractions occurred along the rat duodenum with a frequency of 36 +/- 2 cpm and strain rate amplitude of 26.8 +/- 8.0% s-1. These contractions occurred at fixed locations along the duodenum forming columns on the longitudinal strain rate map. The strain rate activity had local maxima at 46 points spaced at 7.7 +/- 4.0 mm intervals along the duodenum and were uncoordinated between neighboring domains. Similarly disposed, less distinct, longitudinal contractions occurred in the guinea pig duodenum at a frequency of 25.2 +/- 6.6 cpm with amplitude 6.8 +/- 3.6% s-1 but these were generally accompanied by numerous circular contractions that were distributed over 45 fixed locations and occurred with a frequency of 9 +/- 3 cpm. Isolated static circular muscle contractions also occurred but at a lower rate in the rat than the guinea pig. Both types of contractions propagated after dosage with tetrodotoxin, lidocaine, atropine, or apamin. Conclusions & Inferences Localized contractions during segmental and pendular activity had some features of the spike patches that are normally associated with slow wave propagation. However, the commencement of propagation following administration of neural blocking agents and cholinergic inhibitors indicates their localization is maintained by inhibitory elements of the enteric nervous system.