Abstract

PIP: Rhesus monkeys weighing 6-8 kg and demonstrating regular menstrual cycles were used to delineate the relationships between the circadian patterns in spontaneous uterine activity, the urinary excretion of 2 catecholamines, norepinephrine and epinephrine, and the alterations in adrenergic neuroreceptors. In Experiment 1 norepinephrine and epinephrine concentrations were determined by the Zuspan and Cooley method. These values were correlated with the circadian patterns of spontaneous uterine activity. In Experiment 2 the effect on the circadian pattern evidenced by spontaneous uterine activity of pharmacologic depletion of catecholamines as well as selective blocking of alpha and beta adrenergic receptors, were evaluated. Constant iv infusion of reserpine was used to suppress catecholamines as well as selective blocking of alpha and beta adrenergic receptors, were evaluated. Constant iv infusion of reserpine was used to suppress catecholamines. In Experiment 1, lowest values occurred in the secretory phase during the periods of darkness, and highest values occurred in the proliferative phase during periods of light. Intrauterine pressure and norepinephrine excretion consistently exhibited diurnal variations conforming to sine curves and were statistically correlated (r = .838, p less than .001). In Experiment 2 the continuous infusion of reserpine produced a dose-related reduction in the average values and circadian patterns of uterine activity and norepinephrine and epinephrine excretion. Baseline resting pressures were reduced by phentolamine infusion. The frequency of contractions were also reduced and the diurnal variations of uterine activity abolished. Beta blockade increased the resting pressure and the amplitude of contractions. The results suggest that adrenergic receptors and catecholamines have a causal role in the occurrence of spontaneous variations in and the establishment of the circadian pattern of uterine activity.