The role of the ovarian horn locus in regulation of spontaneous electric activity of myometrial rhythmogenic areas

Abstract

The role of the ovarian area of the uterine horn in coordination of spontaneous activity of myometrial rhythmogenic areas was studied in nonpregnant rats both under normal conditions and following transection of the uterine horn in its middle part to isolate the ovarian locus from the distally located uterine active areas. The effect of oxytocin as a factor that reveals a leading role of the ovarian locus in synchronization of myometrial spontaneous activity was studied under the above conditions. Intravenous oxytocin administration (10–1 μg/kg) under normal conditions promotes a considerable increase in the peak amplitude and mean rise rate in all the three rhythmogenic areas (%; ovarian horn area—by 148.63 ± 6.1, p ≤ 0.001 and 141.04 ± 7.6, p ≤ 0.01; cervical horn area—by 143.85 ± 3.5, p ≤ 0.001 and 146.89 ± 8.5, p ≤ 0.001; uterine corpus—by 146.20 ± 7.2, p ≤ 0.001 and 139.73 ± 8.2, p ≤ 0.05, respectively). Under the same conditions, also there is a similar increase in the active state duration in all the three areas (%; 132.70 ± 4.5, p ≤ 0.05; 124.90 ± 9.6, p ≤ 0.05; 128.03 ± 7.2, p ≤ 0.05, respectively). Following transection of the uterine horn, oxytocin administration causes an increase in all the three activity indicators only in the ovarian horn area (%; 134.86 ± 2.5, p ≤ 0.05; 139.49 ± 4.5, p ≤ 0.001; 123.8 ± 7.3, p ≤ 0.05, respectively). In the cervical horn area and uterine corpus, no appreciable changes in these indicators were detected under both conditions. We believe that the ovarian locus is involved in coordination of activities of all the three myometrial rhythmogenic areas as revealed by oxytocin.