Submandibular responses to stimulation of the parasympathetic innervation in anesthetized sheep.
Submandibular secretory and vascular responses to stimulation of the parasympathetic innervation and the output of vasoactive intestinal peptide (VIP) were investigated in anaesthetized sheep in the presence and absence of atropine (>/=0.5 mg/kg). In the absence of atropine, parasympathetic stimulation caused an increase in the flow of saliva and a decrease in submandibular vascular resistance; the latter response persisted after the administration of atropine and was then significantly reduced at the lowest but not at the higher frequencies tested. The output of VIP from the gland was frequency dependent over the range of 10-20 Hz (continuously) and significantly increased after atropine (P < 0.02). Furthermore, the fall in vascular resistance was linearly related to log VIP output after total muscarinic blockade. Intracarotid infusions of synthetic VIP produced dose-dependent falls in submandibular vascular resistance, together with a corresponding increase in submandibular blood flow. It is concluded that the atropine-resistant vasodilatation that occurs in this gland during parasympathetic stimulation is likely to be due largely, if not entirely, to the release of VIP.
Edwards
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Physiological Laboratory, Downing St., Cambridge CB2 3EG, UK.
Corkery
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Edwards
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D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002320:Cardiovascular Physiological Phenomena; D002339:Carotid Arteries; D002814:Chorda Tympani Nerve / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D004558:Electric Stimulation / Q000379:methods; D007269:Injections, Intra-Arterial; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects; D012463:Saliva / Q000187:drug effects / Q000378:metabolism; D012756:Sheep; D013363:Submandibular Gland / Q000098:blood supply / Q000378:metabolism / Q000502:physiology*; D014655:Vascular Resistance; D014660:Vasoactive Intestinal Peptide / Q000008:administration & dosage / Q000138:chemical synthesis / Q000378:metabolism
D018727:Muscarinic Antagonists; D014660:Vasoactive Intestinal Peptide; D001285:Atropine