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

Abstract

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) alpha- and beta-adrenoceptors do not contribute to sympathetic inhibition of parasympathetic vasodilation, and thus some other types of receptors must be involved in this response.

Interactions between β-adrenergic vasodilation and cervical sympathetic nerves are mediated by α2-adrenoceptors in the rat masseter muscle

“…2 a, 3 ). The increased level of the MBF is comparable with the spontaneous activity in the CST fibers innervating the masseter vasculature as electrical stimulation of the peripheral cut end of the CST restored the basal level of the MBF to pre-sectioned values, as also demonstrated previously [ 6 ]. The increases in the basal level of the MBF were caused by either high or low spontaneous activity (5:2) in the CST (Fig.…”

Interactions between β-adrenergic vasodilation and cervical sympathetic nerves are mediated by α2-adrenoceptors in the rat masseter muscle

“…2 a, 3 ). The increased level of the MBF is comparable with the spontaneous activity in the CST fibers innervating the masseter vasculature as electrical stimulation of the peripheral cut end of the CST restored the basal level of the MBF to pre-sectioned values, as also demonstrated previously [ 6 ]. The increases in the basal level of the MBF were caused by either high or low spontaneous activity (5:2) in the CST (Fig.…”

GABAB receptors in the NTS mediate the inhibitory effect of trigeminal nociceptive inputs on parasympathetic reflex vasodilation in the rat masseter muscle

“…These observations suggest that the evoked MBF increases as a result of "vasodilation." Although blood vessels in the masseter muscle are innervated with sympathetic postganglionic neurons derived from the superior cervical ganglion, these neurons did not contribute to the observed MBF increases evoked by cVN stimulation, since bilateral sectioning of the CST in the present study cuts the preganglionic inputs to the superior cervical ganglion, which projects postganglionic fibers to the cranial circulation (see MATERIALS AND METHODS), and electrical stimulation of the CST consistently reduced MBF, as reported by our previous reports (14,15). Therefore, we hypothesize that the cVN stimulationinduced vasodilation in the masseter muscle is mediated by a mechanism involving a parasympathetic reflex.…”

The identification and neurochemical characterization of central neurons that target parasympathetic preganglionic neurons involved in the regulation of choroidal blood flow in the rat eye using pseudorabies virus, immunolabeling and conventional pathway tracing methods

“…The selectivity of our labeling, however, provides insight into the circuitry and mechanisms specifically underlying parasympathetic control of choroidal blood flow (ChBF) via SSN. As discussed below in more detail, the cell groups in which we observed labeled neurons after injections of PRV restricted to choroid have previously been implicated in the parasympathetic control of other cranial autonomic functions, including blood flow in other cranial structures (Jansen et al, 1992 ; Haxhiu et al, 1993 ; Izumi and Karita, 1994 ; Agassandian et al, 2003 ; Ishii et al, 2007 ), and in the sympathetic control of the peripheral systemic circulation (Strack et al, 1989a , b ; Kerman et al, 2003 ).…”

Interactions between β-adrenergic vasodilation and cervical sympathetic nerves are mediated by α2-adrenoceptors in the rat masseter muscle

“…2 a, 3 ). The increased level of the MBF is comparable with the spontaneous activity in the CST fibers innervating the masseter vasculature as electrical stimulation of the peripheral cut end of the CST restored the basal level of the MBF to pre-sectioned values, as also demonstrated previously [ 6 ]. The increases in the basal level of the MBF were caused by either high or low spontaneous activity (5:2) in the CST (Fig.…”

GABAB receptors in the NTS mediate the inhibitory effect of trigeminal nociceptive inputs on parasympathetic reflex vasodilation in the rat masseter muscle

“…These observations suggest that the evoked MBF increases as a result of "vasodilation." Although blood vessels in the masseter muscle are innervated with sympathetic postganglionic neurons derived from the superior cervical ganglion, these neurons did not contribute to the observed MBF increases evoked by cVN stimulation, since bilateral sectioning of the CST in the present study cuts the preganglionic inputs to the superior cervical ganglion, which projects postganglionic fibers to the cranial circulation (see MATERIALS AND METHODS), and electrical stimulation of the CST consistently reduced MBF, as reported by our previous reports (14,15). Therefore, we hypothesize that the cVN stimulationinduced vasodilation in the masseter muscle is mediated by a mechanism involving a parasympathetic reflex.…”

The identification and neurochemical characterization of central neurons that target parasympathetic preganglionic neurons involved in the regulation of choroidal blood flow in the rat eye using pseudorabies virus, immunolabeling and conventional pathway tracing methods

“…The selectivity of our labeling, however, provides insight into the circuitry and mechanisms specifically underlying parasympathetic control of choroidal blood flow (ChBF) via SSN. As discussed below in more detail, the cell groups in which we observed labeled neurons after injections of PRV restricted to choroid have previously been implicated in the parasympathetic control of other cranial autonomic functions, including blood flow in other cranial structures (Jansen et al, 1992 ; Haxhiu et al, 1993 ; Izumi and Karita, 1994 ; Agassandian et al, 2003 ; Ishii et al, 2007 ), and in the sympathetic control of the peripheral systemic circulation (Strack et al, 1989a , b ; Kerman et al, 2003 ).…”

Interactions between β-adrenergic vasodilation and cervical sympathetic nerves are mediated by α2-adrenoceptors in the rat masseter muscle

“…2 a, 3 ). The increased level of the MBF is comparable with the spontaneous activity in the CST fibers innervating the masseter vasculature as electrical stimulation of the peripheral cut end of the CST restored the basal level of the MBF to pre-sectioned values, as also demonstrated previously [ 6 ]. The increases in the basal level of the MBF were caused by either high or low spontaneous activity (5:2) in the CST (Fig.…”

GABAB receptors in the NTS mediate the inhibitory effect of trigeminal nociceptive inputs on parasympathetic reflex vasodilation in the rat masseter muscle

“…These observations suggest that the evoked MBF increases as a result of "vasodilation." Although blood vessels in the masseter muscle are innervated with sympathetic postganglionic neurons derived from the superior cervical ganglion, these neurons did not contribute to the observed MBF increases evoked by cVN stimulation, since bilateral sectioning of the CST in the present study cuts the preganglionic inputs to the superior cervical ganglion, which projects postganglionic fibers to the cranial circulation (see MATERIALS AND METHODS), and electrical stimulation of the CST consistently reduced MBF, as reported by our previous reports (14,15). Therefore, we hypothesize that the cVN stimulationinduced vasodilation in the masseter muscle is mediated by a mechanism involving a parasympathetic reflex.…”

The identification and neurochemical characterization of central neurons that target parasympathetic preganglionic neurons involved in the regulation of choroidal blood flow in the rat eye using pseudorabies virus, immunolabeling and conventional pathway tracing methods

“…The selectivity of our labeling, however, provides insight into the circuitry and mechanisms specifically underlying parasympathetic control of choroidal blood flow (ChBF) via SSN. As discussed below in more detail, the cell groups in which we observed labeled neurons after injections of PRV restricted to choroid have previously been implicated in the parasympathetic control of other cranial autonomic functions, including blood flow in other cranial structures (Jansen et al, 1992 ; Haxhiu et al, 1993 ; Izumi and Karita, 1994 ; Agassandian et al, 2003 ; Ishii et al, 2007 ), and in the sympathetic control of the peripheral systemic circulation (Strack et al, 1989a , b ; Kerman et al, 2003 ).…”