Lack of spontaneous ovarian contractions in the baboon.

Histological observations on the ovaries of various species reveal smooth muscle fibres throughout the stroma and theca interna (Lambertsen, Greenbaum, Wright & Wallach, 1976). Ovarian contractions have been observed and recorded in vitro and in vivo in an equally diverse number of species (Wright, Wallach, Fromm & Jeutter, 1976). Although the physiological significance of spontaneous ovarian contractions is not known it has been suggested that they may be in some way related to the mechanism of ovulation (Lipner & Maxwell, 1960). This speculation is supported by the observation that the frequency of spontaneous ovarian contractions increases about the time of ovulation (Virutamasen, Wright & Wallach, 1973). The methods which have been used to monitor ovarian contractions in vivo are not capable of clearly delineating contractions of ovarian origin from ovarian movement resulting from contrac¬ tions of the supporting mesenteries and ligaments of the ovary. Recent work in our laboratory has led to the development of very small doughnut-shaped carbon-impregnated silicone-rubber (Silastic S-2086, Dow Corning) transducers which are highly sensitive to direct contractile activity and rela¬ tively insensitive to movement. Instrumentation which provides for the biotelemetric transmission of the signal from these transducers permits their use in unrestrained, unanaesthetized animals for long periods of time. Moreover, because of the small size of the sensor (approximately 1200 pm in diameter), recording of contractile activity can be made at a precise location of interest without sig¬ nificant interference from movement of the structure being monitored. The method of making and calibrating the transducers and a description of the dual-channel biotelemetric system used for signal processing has been previously described (Blair & Beck, 1976; Blair, Gilliland & Sauer, 1976). To test the question of whether or not ovarian tissues of the baboon (Papio papio) undergo spontaneous contractions, transducers of this type were positioned within the ovarian stroma of 3 adult baboons and observations were made on the contractile activity over a 30-day period. All 3 females were experiencing normal menstrual cycles. Two transducers were placed in each animal :