Presence of neuropeptide Y in the rat seminal vesicle and its effects on noradrenaline- and nerve-induced contractions.
1. Immunohistochemical and functional studies have been performed to localize and determine the effects of neuropeptide Y (NPY) in the rat seminal vesicle. 2. An abundant presence of NPY-immunoreactive nerves, mainly concentrated in the smooth muscle layer of the seminal vesicle was found. Chronic 6-hydroxydopamine treatment (four doses of 50 mg kg-1 i.p. on days 1, 2, 4 and 6; rats killed one week after the last injection) led to a large reduction but not abolition of the NPY-immunoreactivity. 3. NPY (1-250 nM) did not affect the resting tone of the seminal vesicle. 4. The seminal vesicle was contracted by electrical field stimulation (EFS) and by exposure to 5 microM noradrenaline (NA). These contractions were abolished by phentolamine (1 microM). Tetrodotoxin (0.5 microM) abolished EFS-evoked contractions but did not affect NA-evoked contractions. 5. Seminal vesicles, from animals chronically-treated with reserpine (5 mg kg-1 i.p. on days 1 and 2; rats killed on day 3), were contracted by NA but not by EFS. 6. NPY (0.25-250 nM), concentration-dependently, inhibited EFS-evoked contractions by up to 70% maximum inhibition. Contractions evoked by EFS with short trains of pulses were inhibited by NPY to a greater degree than those with longer trains. 7. NPY had no significant effect on NA-evoked contractions. 8. These data provide strong evidence that the motor transmission in rat seminal vesicle is predominantly if not exclusively, adrenergic. It is further concluded that a rich NPY-containing innervation is present in the smooth muscle layer of rat seminal vesicle. The primary effect of NPY is modulation of adrenergic motor transmission by a prejunctional inhibition of NA release.
Department of Pharmacological Sciences, Medical School, University of Newcastle upon Tyne.
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Iravani
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D000818:Animals; D002118:Calcium / Q000378:metabolism; D004558:Electric Stimulation; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009478:Neuropeptide Y / Q000032:analysis / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012669:Seminal Vesicles / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology
D009478:Neuropeptide Y; D002118:Calcium; D009638:Norepinephrine