Oxytocin modulates oxytocin neurons in the paraventricular nuclei of female rats throughout pregnancy and parturition

Article Abstract:

Oxytocin neurons that operate by negative feedback in virgin and pregnant rats may switch to a positive feedback mechanism in rats that are in labor or lactating. The hormone oxytocin plays an important role in inducing uterine contractions and lactation. The response of oxytocin neurons to oxytocin was measured in virgin, pregnant and delivering rats. In the virgin rats, the firing rates decreased in response to oxytocin in 12 neurons, increased in one and remained the same in four. On day 21 of pregnancy, firing rates decreased in 20 neurons, increased in two and remained the same in four. In the delivering rats, firing rates increased in seven neurons and only one neuron showed no response to oxytocin. Oxytocin increased the firing rates of oxytocin neurons in lactating rats. Several months after delivery however, firing rates of oxytocin neurons decreased in response to oxytocin.

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Comparison of in vitro and in vivo inhibitory effects of peptide and nonpeptide oxytocin antagonists on radioligand binding and uterine contractility of rats during pregnancy

Article Abstract:

Peptidyl and nonpeptidyl oxytocin may work together to inhibit uterine contractions and may become a treatment for preterm labor. Researchers observed the effects of peptidyl and nonpeptidyl oxytocin and oxytocin blockers in pregnant rats and in the laboratory. Peptidyl oxytocin was found to stop uterine contractions by blocking oxytocin receptors. High levels of nonpeptidyl oxytocin further inhibited contractions. Peptidyl and nonpeptidyl oxytocin did not inhibit uterine contractions in rats in earlier pregnancy, perhaps because oxytocin receptors are fewer in early pregnancy.

Hormone antagonists, Uterus, Uterine contractions

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Oxytocin enhances action potentials in pregnant human myometrium - a study with microelectrodes

Article Abstract:

Oxytocin appears to affect the electrical properties of uterine tissue cells. Uterine tissue samples from 15 patients undergoing full-term cesareans were removed before labor began. Electrical activity was monitored in the samples when exposed to varying levels of oxytocin. Exposure to low levels of oxytocin resulted in either additional electrical spikes, more frequent electrical spikes, or higher and longer electrical spikes. Exposure to higher concentrations of oxytocin reversed the membranes' polarity allowing substances to pass more freely through it.

Measurement, Myometrium, Action potentials (Electrophysiology), Action potentials

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