Uterine Motility of the Estrogenized Rabbit

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Abstract
The amplitude of the uterine contraction elicited by a few seconds stimulation of the hypogastric nerve depends on: (1) the stimulus frequency. the contraction being maximal at 30 to 50 cps; (2) the excitability of the myometrium, being increased in a period from 20 to 60 sec following a preceding stimulus, and; (3) the degree of uterine distension. Whereas stimulation for a few seconds elicits a single contraction, prolonged stimulation (for several minutes) at low frequencies (5–10 cps) evokes a series of rhythmic contractions. Prolonged stimulation at frequencies above 10 cps causes in addition a transient elevation of the minimum pressure. I. v. administration of cocaine does not potentiate the response to hypogastric nerve stimulation, whereas potentiation by cocaine is obtained when the agent are applied intra‐uterinely. This effect, as well as the response to adrenergic blocking agents, indicate the presence of adrenergic fibres in the hypogastric nerve supplying the myometrium. Evidence for cholinergic fibres to uterus in the hypogastric nerve was not obtained. The uterine response to splanchnic nerve stimulation differs from the response to hypogastric nerve stimulation by a longer latency and by a more gradual onset.