title: Cholinergic and VIPergic vasodilator actions of parasympathetic nerves on the thyroid blood flow in rats.
abstract: The present experiment was performed to investigate the effect of stimulating the parasympathetic superior laryngeal nerve (SLN) on thyroid blood flow and its mediator substances in urethane-chloralose anesthetized rats. Thyroid blood flow was measured by counting number of blood drops from a thin catheter inserted into the thyroid vein. SLNs were cut bilaterally and their peripheral portions were electrically stimulated. Electrical stimulations (intensity, 10 V; pulse duration, 0.5 ms) of SLNs increased thyroid blood flow in a frequency-dependent manner as stimulus frequencies increased from 2 to 40 Hz. The intravenous administration of atropine (0.5 mg/kg) reduced these responses, but did not abolish them. The basal secretion rate of vasoactive intestinal peptide (VIP) from thyroid glands in the resting state was nearly zero (0.25 +/- 0.14 pg/(kg.min)). SLN stimulation increased markedly the VIP secretion rate to 3.40 +/- 0.64 pg/(kg.min). The VIP secretion responses evoked by SLN stimulation remained in atropinized rats. Furthermore, exogenously applied VIP increased the thyroid blood flow dose-dependently. These results suggest that SLN stimulation increases the thyroid blood flow by dilating thyroid blood vessels via activation of cholinergic and non-cholinergic (probably VIP-containing) nerve fibers. Thus, these parasympathetic vasodilation systems may play a supplementary role in regulating the secretion of thyroid hormone by changing the thyroid blood flow in addition to the role of hormonal regulation by the thyroid stimulating hormone (TSH).
authors.affiliation: Department of Physiology, Tokyo Metropolitan Institute of Gerontology, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Ito
authors.forename: K
authors.initials: K
authors.lastname: Matsuda
authors.forename: A
authors.initials: A
authors.lastname: Sato
authors.forename: H
authors.initials: H
authors.lastname: Tohgi
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D007823:Laryngeal Nerves / Q000502:physiology; D008297:Male; D009333:Neck / Q000294:innervation; D010275:Parasympathetic Nervous System / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012039:Regional Blood Flow / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000502:physiology; D013961:Thyroid Gland / Q000098:blood supply* / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D014664:Vasodilation
chemical_list: D014660:Vasoactive Intestinal Peptide