Does the guinea-pig ileum obey the law of the intestine?
1. We report the first simultaneous mechanical reflex responses of the longitudinal muscle (LM) and circular muscle (CM) layers of the guinea-pig ileum following mucosal stimulation and distension in vitro. 2. Dissection techniques were used to prevent mechanical interaction between the LM and CM layers both oral and anal to a stimulus site. 3. All graded stimuli produced graded contractions of both the LM and CM orally and anally to the stimulus. Contractions occurred synchronously in the LM and CM and under no circumstances were inhibitory responses recorded in either muscle layer, despite the presence of ongoing cholinergic tone in both the LM and CM. Contractions were abolished by tetrodotoxin (1.6 microM). 4. Local brush stroking of the mucosa evoked a peristaltic wave which readily conducted distally over 13 cm, without the presence of fluid in the lumen. No descending relaxation was observed. 5. Apamin (300 nM) disrupted evoked peristaltic waves and significantly increased the r
