6-Hydroxydopamine, when injected at 14:00 h on Days 21 and 22 of pregnancy in the rat (2 x 50 mg/kg), markedly decreased plasma and uterine noradrenaline concentrations (-60% and -82% respectively; P < 0.001). As a consequence of this treatment, there was severe disturbance in the distribution pattern of parturitions: 61% of rats had suppressed parturition and 31% of rats displayed a lengthened or interrupted labour. A bolus dose of prazosin (3 mg/kg) administered at 12:00 h on Day 22 completely blocked the normal process of parturition throughout the next 6 h, a result which is compatible with the half-life of the drug (2.9 ± 0.8 h). Administration of phentolamine (3 mg/kg) at term induced a significant decrease of uterine activity (frequency x duration of bursts of spike potentials) as revealed by electromyographic recordings in vivo. These results suggest that noradrenaline released from sympathetic nerve terminals interacts with α-adrenoceptors located post-synaptically to improve the overall excitability of the myometrium at the onset of labour.
CITATION STYLE
Legrand, C., & Maltier, J. P. (1986). Evidence for a noradrenergic transmission in the control of parturition in the rat. Journal of Reproduction and Fertility, 76(1), 415–424. https://doi.org/10.1530/jrf.0.0760415
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