Development of a new telemetry recording system for measuring of gastrointestinal contractile activity in unrestrained and conscious small animals

Abstract

Myoelectrogram, strain gauge force transducer or manometry has been commonly used to record contractile activity of the gastrointestinal (GI) tract in small animals, but protecting the lead wires and tubes is troublesome when conducting experiments. To solve this problem, we have developed a new telementric recorder which can be implanted in the abdominal cavity of a small animal. The elemeter is a cylinder (phi 10 x 35 mm) with a strain gauge force transducer (4 x 3 mm) connected by fine lead wires. The telemeter includes a battery and amplification, transmission and power supply circuit to the transducer. The battery has a 1,500 hr life and is designed to be turned on and off from outside the body by means of a magnetic switch. The device weights 4 g and is waterproofed with silicon. Five male Wister rats weighing 300-400 g were used. Under general anesthesic, the force transducer was sutured onto the serosa in the gastric antrum, and the telemeter was fixed in the corner of the peritoneal cavity. During measurement, the rats were housed in individual cages under unrestrained conditions and the cage was placed on the receiver. Gastric motility could be continuously recorded for up to 60 days, although body movements sometimes affected the recordings slightly due to adhesion. There was no noticeable trouble related to the device implanted in the abdominal cavity. Gastric motility recorded with this telemeter was identical with that measured by other devices, and consisted of two different patterns, the fasted and fed patterns divided into two phases, as reported previously. In the fasted state, cyclic occurrence of intense contractions was observed, and regular phasic contractions were observed in the fed state. Bethanechol induced strong contractions and atropine inhibited contractile activity. The newly developed telemeter is a useful and reliable device to use in measuring GI motility in small animals.