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Evidence against vasoactive intestinal polypeptide as the relaxant neurotransmitter in human cavernosal smooth muscle
Author(s) -
Pickard R.S.,
Powell P.H.,
Zar M.A.
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb12831.x
Subject(s) - vasoactive intestinal peptide , neurotransmitter , endocrinology , medicine , muscle relaxant , acetylcholine , muscle relaxation , stimulation , nitric oxide , cyclic guanosine monophosphate , nitroarginine , nitric oxide synthase , chemistry , neuropeptide , biology , receptor , pharmacology , central nervous system
1 The putative role of vasoactive intestinal polypeptide (VIP) as the relaxant neurotransmitter in human cavernosal smooth muscle has been studied in isolated tissue preparations. 2 Consistent neurogenic relaxations were evoked by electrical field stimulation (EFS; 2–64 pulses/train, 0.8 ms pulse duration, 10 Hz). VIP (0.1–3 μ m ) relaxed cavernosal smooth muscle in a dose‐dependent fashion. Relaxant responses to both EFS and VIP were reduced in tissue from impotent men. 3 Neurogenic relaxant responses were not diminished in the presence of the VIP‐inactivating peptidase, α‐chymotrypsin (α‐CT, 2 units ml −1 ). In contrast VIP‐induced relaxations were completely abolished. 4 Inhibition of nitric oxide synthase by N G ‐nitro‐ l ‐arginine (30 μ m ), and of guanylate cyclase by methylene blue (50 μ m ) caused highly significant reductions of neurogenic relaxant responses whereas VIP‐evoked relaxations were unaffected. 5 It is concluded that VIP‐evoked relaxations are not mediated by the NO‐guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) pathway and that VIP release is not essential for neurogenic relaxation of human cavernosal smooth muscle. VIP does not therefore act as the major relaxant neurotransmitter in this tissue.