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This Article Full Text Full Text (PDF) All Versions of this Article: 293/2/R729    most recent 00866.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Ishii, H. Articles by Izumi, H. Search for Related Content PubMed PubMed Citation Articles by Ishii, H. Articles by Izumi, H.

NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Inhibitory effects of excess sympathetic activity on parasympathetic vasodilation in the rat masseter muscle

¹Department of Oral Physiology, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido, Japan; and ²Department of Pain Control, Tohoku University, Graduate School of Medicine, Sendai, Japan

Submitted 13 December 2006 ; accepted in final form 30 May 2007

The present study was designed to examine the effect of sympathetic tonic activity on parasympathetic vasodilation evoked by the trigeminal-mediated reflex in the masseter muscle in urethane-anesthetized rats. Sectioning of the superior cervical sympathetic trunk (CST) ipsilaterally increased the basal level of blood flow in the masseter muscle (MBF). Electrical stimulation of the peripheral cut end of the CST for 2 min using 2-ms pulses ipsilaterally decreased in a dependent manner the intensity (0.5–10 V) and frequency (0.1–5 Hz) of the MBF. The CST stimulation for 2 min at <0.5 Hz with 5 V using 2-ms pulses seems to be comparable with the spontaneous activity in the CST fibers innervating the masseter vasculature, because this stimulation restored the basal level of the MBF to the presectioned values. Parasympathetic vasodilation evoked by electrical stimulation of the central cut end of the lingual nerve in the masseter muscle was markedly reduced by CST stimulation for 2 min with 5 V using 2-ms pulses in a frequency-dependent manner (0.5–5 Hz). Intravenous administration of phentolamine significantly reduced the vasoconstriction induced by CST stimulation in a dose-dependent manner (0.1–1 mg/kg), but pretreatment with either phentolamine or propranolol failed to affect the sympathetic inhibition of the parasympathetic vasodilation. Our results suggest that 1) excess sympathetic activity inhibits parasympathetic vasodilation in the masseter muscle, and 2) - and -adrenoceptors do not contribute to sympathetic inhibition of parasympathetic vasodilation, and thus some other types of receptors must be involved in this response.

superior cervical sympathetic trunk; vasoconstrictor fiber; adrenoceptors; trigeminal-mediated reflex; jaw muscle