Figure 1. Diagram of the three types of preparation used to study the effects of sympathetic nerves on intestinal motility.

A, apparatus used to simultaneously record longitudinal and circular muscle contractions in intact tubes of intestine. A balloon catheter recorded circular muscle activity (as pressure changes, oral end). An isotonic transducer connected to the intestinal wall via a thread and pulley recorded longitudinal muscle length in the same region. Electrodes were used to stimulate both enteric nerves (transmural stimulation) and the perivascular mesenteric nerves. In some experiments an anally placed balloon catheter was used to provide a distension stimulus. B, preparation used to record ascending excitatory reflexes in flat sheets of intestine. A hemispherical balloon set into the base of the bath recorded circular muscle activity (oral end). Distensions were applied via another balloon at the anal end and an electrode used to stimulate the mesenteric nerves. C, apparatus to record ascending EJPs and descending IJPs in the circular muscle. Distensions were applied to the gut wall at two sites in each of two stimulation chambers and reflex responses recorded at the opposite end of the preparation. When the preparation was oriented so that recordings were made at the oral end, ascending EJPs were recorded, and in the opposite orientation the responses seen were IJPs.