Figure 1.

Experimental setups. (A) Effect of a fecal pellet on the CMMC. An epoxy-coated fecal pellet attached to a silk thread was inserted into an isolated segment of colon and was fixed in position with a pin when it reached the middle of the colon. Isometric tension transducers monitored CM tension before and after insertion of the pellet. (B) Partitioned bath. An epoxy-coated fecal pellet was held in position between the 2 partitions by attaching a thread via a pulley to a tension transducer. (C) Mucosal and stretch reflex. A section of the colon was cut open and pinned with the mucosa uppermost, allowing mechanical stimulation with a brush. Circumferential stretch was applied to one edge of the opened region by attaching it to a pulley system to which weights could be added. Tension transducers monitored contractile activity. (D) Microelectrode recordings made on either side of a fecal pellet. Two 10-mm sections of colon were cut open, on either side of a fecal pellet, and pinned circumferentially, with the serosa uppermost, so that electrical activity could be recorded from the underlying CM. (E) Microelectrode recordings from preparations without the mucosa. The mucosa was dissected away from the colon, which was pinned circumferentially. Microelectrode recordings were made 10-mm anal of transmural stimulating electrodes (tms).