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Biology of Reproduction, Vol 3, 13-22, Copyright © 1970 by Society for the Study of Reproduction
1 Division of Biological and Medical Sciences, Brown University,
Providence, Rhode Island 02912 The effects of hypogastric nerve stimulation on the uterus in the anesthetized guinea
pig in estrus are described. Electrical stimulation at frequencies between 1 and 30 pulses
per second (pps) with an intensity of 1.5 mA and pulse duration of 1.5 msec for periods
up to 5 min causes either an initiation of or an increase in uterine motility. These effects
of nerve stimulation are prevented by an alpha adrenoceptor blocking agent (phentolamine 5 x 10-6 g/kg iv). Uterine responses to nerve stimulation at frequencies above
15 pps were not maintained, probably because of the accompanying vascular changes in
the uterus. Stimulation of the hypogastric nerves at frequencies between 1 and 6 pps and a lower
intensity (1.0 mA) does not elicit uterine contractions per se, but instead increases uterine
sensitivity to oxytocin. This increase in sensitivity is slight during stimulation at 1 pps,
but becomes highly significant (p < .001) during stimulation at 4 and 6 pps. These results
provide indirect evidence that adrenergic nerve impulses can modulate the sensitivity of
the myometrial cells to oxytocin. The increase in uterine sensitivity to oxytocin during hypogastric nerve stimulation at
4 pps (1.0 mA) is abolished by an alpha adrenoceptor blocking agent (phentolamine 5 x
10-6 g/kg iv) and potentiated by a beta adrenoceptor blocking agent (propranolol 5 x
10-6 g/kg iv). Therefore, the increase in sensitivity is mediated by interaction of the
neurotransmitter norepinephrine with alpha (stimulatory) adrenoceptor sites in the
myometrium. The ganglion-blocking agent hexamethonium (5 mg/kg iv) prevents the increase in
uterine sensitivity to oxytocin during hypogastric nerve stimulation. These results show
that the increase in sensitivity is mediated by stimulation of preganglionic fibers in the
hypogastric nerves. One physiological function of adrenergic nerve activity in the myometrium might be a
modulation of myometrial excitability to oxytocin and possibly to other agents as well.
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  M Dupuis, E Houdeau, and S Mhaouty-Kodja Increased potency of {alpha}1-adrenergic receptors to induce inositol phosphates production correlates with the up-regulation of {alpha}1d/Gh{alpha}/phospholipase C{delta}1 signaling pathway in term rat myometrium Reproduction, January 1, 2008; 135(1): 55 - 62. [Abstract] [Full Text] [PDF]
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