Effect of the parasympathetic vasodilation on temperature regulation via trigeminal afferents in the orofacial area

Figures

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  Fig. 1. Schematic representation of the electrical stimulation sites and measurement sites of both local blood flow (BF) and temperature (Tm) in rats. The stimulation sites were as follows: (i) central cut end of the lingual nerve (LN) and (ii) peripheral cut end of the superior cervical sympathetic trunk (CST). Local BF and Tm were measured in the (iii) lower lip (Real image), using laser speckle imaging (LSI) and a thermometer, respectively. The continuous lines indicate a trigeminal sensory inputs to the trigeminal spinal nucleus (Vsp) in the brainstem and b parasympathetic vasodilator fiber to the lower lip from the salivatory nuclei (SN). The dashed lines indicate sympathetic vasoconstrictor fiber to the lower lip from the superior cervical ganglion (SCG) of the superior CST (c). OG otic ganglion, TG trigeminal ganglion, V trigeminal nerve root, VII facial nerve root, IX glossopharyngeal nerve root. Modified from Ishii et al. [17]

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  Fig. 2. Relationships between hemodynamics and the Tm during trigeminal afferent inputs in the orofacial tissues in the rat. a Illustration of the area in the mandibular including lower lip in a supine rat. b Typical example of the real image and speckle images of the BF in the lower lip at the basal level (rest) and produced by left LN stimulation (LN stim.) for 20 s with a supramaximal voltage (20 V) at 20 Hz using 2-ms pulses. Scale bars represent 3.5 mm. c Changes in BF (a.u.; arbitrary units), vascular conductance (VC; a.u./mmHg) and Tm (°C) in the lower lip extracted from a region of interest (ROI) indicated by the white circles in b, and systemic arterial blood pressure (SABP; mmHg) evoked by LN stimulation (arrow head with dashed line). The white traces indicate the mean VC and Tm at the measuring site. d Mean ± standard error of the mean (SEM) of ∆BF, ∆VC, and ∆Tm in the lower lip (black symbols) and the skin of the dorsum of the foot (gray symbols) evoked by LN stimulation at 20 V and various frequencies (1–20 Hz; n = 6 in each group). The responses evoked by LN stimulation were determined by calculating the difference between the maximum value during the 10 min after…

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  Fig. 3. Effects of pharmacological blocking agents on the increase in BF and Tm evoked by LN stimulation in the lower lip. Typical examples of the effects of intravenous administration of hexamethonium (C6) at 10 mg/ml (a) and atropine (b) at 100 μg/ml for 10 min (0.1 ml/min) on changes in the BF, VC, and Tm in the lower lip on the left side evoked by left LN stimulation (20 s, 10 V, 20 Hz, 2-ms). c Mean ± SEM of changes in the ∆BF, ∆VC, and ∆Tm in the lower lip evoked by LN stimulation with administration of C6 (black bars) and atropine (gray bars; n = 6 in each group). The responses evoked by LN stimulation with C6 and atropine were determined by calculating the differences between the maximum values during 10 min after stimulation with C6 and atropine and the baseline values. Each value is expressed as a percentage of the response before treatment (control). Statistical significance was assessed by ANOVA followed by a post-hoc test (Fisher’s PLSD). *P < 0.001 vs. control

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  Fig. 4. Effects of an exogenously applied VIP agonist on the hemodynamics and Tm in the lower lip. a Typical examples of the effects of intravenous administration of VIP agonist (VIP-A) at 5 μg/ml for 10 min (0.1 ml/min) on changes in BF, VC, and Tm in the lower lip on the left side. b Mean ± SEM of changes in the ∆BF, ∆VC, and ∆Tm in the lower lip evoked by the drug at 0.05–5 μg/ml (n = 6 in each group). The responses evoked by the administration of a VIP agonist were determined by calculating the difference between the maximum value during the 10 min after its administration and the value at baseline. *P < 0.05, **P < 0.01 vs. base value

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  Fig. 5. Sympathetic effects on the hemodynamics and Tm in the lower lip, and SABP. a Typical examples of changes in BF, VC, and Tm in the lower lip on the left side, extracted from the ROI indicated by the white circles in Fig. 2b, and SABP evoked by electrical stimulation of the peripheral cut end of the left CST (CST stim.; horizontal bar with dashed lines) for 2 min with a supramaximal voltage (10 V) at 5 Hz using 2-ms pulses. b Mean ± SEM of ∆BF, ∆VC, and ∆Tm in the lower lip (black symbols) evoked by CST stimulation at 10 V and various frequencies (0.5–5 Hz; n = 6 in each group). The responses evoked by CST stimulation were determined by calculating the difference between the maximum value during the 10 min after stimulation and the baseline value. *P < 0.05, **P < 0.01, ***P < 0.001 vs. base value

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  Fig. 6. Interactions between trigeminally mediated parasympathetic vasodilation and sympathetic vasoconstriction in the regulation of the hemodynamics and Tm in the orofacial area. a Typical examples of the changes in BF, VC, and Tm in the lower lip on the left side, and SABP evoked by left CST stimulation (CST stim.) alone (2 min, 10 V, 5 Hz, 2-ms; control) and in combination with left LN stimulation (20 s, 20 V, 20 Hz, 2-ms). Changes (∆) in the parameters were assessed by calculating the sum of the maximum ( +) and minimum (−) values from the baseline in the responses. b Mean data ± SEM of ∆BF, ∆VC, and ∆Tm in the lower lip (black bars) evoked by left CST stimulation alone (control) and in combination with LN stimulation (CST + LN stim.; n = 6 in each group). Statistical significance of the differences from control was assessed by paired Student’s t test. *P < 0.001 vs. control