Quantitative assessment of oxytocin-stimulated oviduct contractions of the ewe by optoelectronic measurements.

Abstract

An optoelectronic instrument, developed to record the muscular activity of the oviduct was used to monitor the effects of oxytocin on oviductal contractions in intact ewes. The transducer consisted of one light emitting diode opposed by two phototransistors and their associated lead wires molded into a “C” shaped cuff in a clear orthodontic resin. The resulting optoelectronic transducer was attached extraluminally to the ampullary region of the oviduct with a cyanoacrylate tissue glue. Lead wires were exteriorized through the flank and connected to the external system electronics to record changes in the light transmittance (LT) resulting from contractions of the oviduct. Recordings from an in vitro experiment using simultaneous force and optoelectronic transducers confirmed that changes in oviduct contractile activity induced by oxytocin were accurately reflected in the optoelectronic transducer signal. Four ewes were instrumented to test how oxytocin treatment during the luteal phase altered the frequency of oviductal contractions. Twenty-four hours after implanting the cuff, logarithmically increasing doses of oxytocin were administered via jugular catheter at 5-hr intervals to each ewe. The ampullary contraction frequency before treatment ranged from 12 to 18 cycles per minute. This contraction frequency increased, and its amplitude decreased within the first min post-oxytocin injection. The mean of the maximum increase in the contraction frequency following injection was 1, 4, 7, 11, 20, 56, 58 and 71 cycles per min corresponding to injections of saline, .11, .33, 1, 3, 9, 27 and 81 USP units of oxytocin. A semi-log plot of the frequency change vs the oxytocin dose exhibited a typical sigmoid dose-response curve. These results illustrate the utility of the optoelectronic transducer as a tool for quantitatively assessing the effects of drugs on oviduct activity in intact unanesthetized animals.