抄録
The functional significance of the sympathetic nerves is still unclear since no sympathetically mediated vasoconstrictor responses have been found to occur reflexly in orofacial tissues in response to a variety of stimuli. We studied the modulating effect of ongoing sympathetic activation on the vasoconstrictor response elicited by brief stimulation of the cervical superior sympathetic trunk (CST) and on that sometimes elicited by electrical stimulation of the peripheral end of the inferior alveolar nerve (IAN). The blood flow increase (antidromic vasodilatation) elicited by inferior alveolar nerve (IAN) stimulation was not affected by ongoing repetitive CST stimulation over the frequency range examined (0.2ms, 10 Hz), although reflex parasympathetic vasodilatation was attenuated. The vasoconstrictor responses elicited by IAN stimulation in some preparations were reduced in a frequency dependent manner (at 0.2ms, 1 Hz) during ongoing CST stimulation (and replaced by vasodilator responses). The vasoconstrictor response evoked directly by brief CST stimulation was attenuated, but not transformed to a vasodilator response, by ongoing CST stimulation. Thus in the cat lower lip 1) sympathetic stimulation attenuated one type of vasodilator response (parasympathetic-mediated vasodilatation), but not another (antidromic vasodilatation), and 2) ongoing sympathetic (CST) stimulation at low frequencies (<1 Hz) prevented further sympathetic-mediated vasoconstriction. [Jpn J Physiol 54 Suppl:S199 (2004)]
