Nifedipine-induced inhibition of parasympathetic-mediated vasodilation in the orofacial areas of the cat.
In anesthetized cats, we 1) compared the effects of antihypertensive agents (nifedipine, clonidine, phentolamine, propranolol, and nitroprusside) on the parasympathetic vasodilations elicited by lingual nerve (LN) stimulation in the lower lip and tongue and 2) investigated the mechanisms underlying the inhibitory effect of nifedipine on parasympathetic lower lip vasodilation. At the doses used, each antihypertensive agent reduced systemic arterial blood pressure by approximately 20 mmHg; however, the parasympathetic vasodilation elicited by LN stimulation was significantly reduced only by nifedipine. This inhibitory effect of nifedipine was not seen when LN was stimulated during ongoing repetitive stimulation of the superior cervical sympathetic trunk at 1-Hz frequency. This suggests that the ability of lip and tongue blood vessels to relax to parasympathetic stimulation is not directly impaired by this calcium channel blocker and that the inhibitory effects of nifedipine seen here probably resulted from an action on postsynaptic sites in vascular smooth muscle that caused a reduction in preexisting sympathetic vasoconstrictor tone (by inhibiting calcium influx into the vascular smooth muscle cell).
Izumi
H
H
Departments of Autonomic Neuroscience and Hospital Pharmacy, Tohoku University School of Dentistry, Sendai 980-8575, Japan. izumi@physiol.dent.tohoku.ac.jp
Nakamura
I
I
D000286:Administration, Sublingual; D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000008:administration & dosage; D002415:Cats; D004558:Electric Stimulation; D005145:Face / Q000098:blood supply / Q000294:innervation / Q000502:physiology*; D007262:Infusions, Intravenous; D008036:Lingual Nerve / Q000502:physiology; D008046:Lip / Q000098:blood supply / Q000294:innervation / Q000502:physiology; D009543:Nifedipine / Q000008:administration & dosage*; D010275:Parasympathetic Nervous System / Q000187:drug effects* / Q000502:physiology; D010276:Parasympatholytics / Q000008:administration & dosage; D012039:Regional Blood Flow; D017783:Superior Cervical Ganglion / Q000502:physiology; D013565:Sympatholytics / Q000008:administration & dosage; D014059:Tongue / Q000098:blood supply / Q000294:innervation / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology; D014665:Vasodilator Agents / Q000008:administration & dosage*
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D002121:Calcium Channel Blockers; D010276:Parasympatholytics; D013565:Sympatholytics; D014665:Vasodilator Agents; D009543:Nifedipine