Neurogenic relaxation mediated by vasoactive intestinal polypeptide (VIP) in the isthmus of the human fallopian tube |
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Authors: | GH Helm R Håkanson S Leander C Owman N-O Sjöberg B Sporrong |
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Institution: | 1. Department of Histology, University of Lund, Lund, Sweden;2. Department of Pharmacology, University of Lund, Lund, Sweden;3. Department of Obstetrics and Gynecology at Lund and Malmö, University of Lund, Lund, Sweden |
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Abstract: | The smooth musculature of the Fallopian tube is important for normal ovum transport, fertilization and implantation. Little is known about the factors controlling the motor activity of the isthmic sphincter. Studies were performed on smooth muscle preparations from the human tube in vitro. Electrical field stimulation of the nerves in the isthmic region reduced the motor activity, particularly in the circular muscle. The response was unaffected by adrenergic and cholinergic antagonists, but blocked by tetrodotoxin, suggesting a neural involvement. Vasoactive intestinal polypeptide (VIP) was considered a likely candidate for the neural mediation of this response in view of the high density of VIP-containing nerve fibres in this region, and in view of the fact that exogenous VIP causes a marked reduction of the tubal motor activity. To test whether VIP might be the endogenous mediator of this effect, nerve stimulation was carried out in the presence of large amounts of exogenous VIP in order to occupy all VIP receptors; the motor inhibitory action of VIP was counteracted by vasopressin. Under these conditions, nerve stimulation failed to reduce isthmic motor activity. This was not due to vasopressin since reduction occurred in the presence of this peptide alone. The results suggest that VIP is responsible for the neurogenic inhibition of motor activity in the isthmus region of the human Fallopian tube. |
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Keywords: | human Fallopian tube smooth muscle activity transmural nerve stimulation non-adrenergic non-cholinergic relaxation vasoactive intestinal polypeptide |
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