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Effects of Isoflurane on Parasympathetic Vasodilatation in the Rat Submandibular Gland

¹ Division of Dento-Oral Anesthesiology, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba, Sendai, 980-8575, Japan;
² Research Fellow of the Japan Society for the Promotion of Science; and
³ Department of Oral Physiology, School of Dentistry, Health Sciences University of Hokkaido, 1757 Kanazawa, Tobetsu, Hokkaido, 061-0293, Japan

View larger version (20K): [in this window] [in a new window]   Figure 1. Schematic representation of the experimental design and effects of isoflurane on the blood flow increase. (A) Schematic representation of the sites of electrical stimulation and blood flow measurements. Stimulation sites: central cut end of the lingual nerve (LN; A) and peripheral cut end of the chorda-lingual nerve (CLN; B). Blood flow measurement sites: blood flow measurements in submandibular gland (SMG). The broken lines indicate parasympathetic fibers [vasodilator fibers to SMG from the superior salivatory nucleus (SSN)]. The solid and dotted lines indicate trigeminal and facial sensory pathways to and within the brain stem. Abbreviations: CT, chorda tympani; LDF, laser-Doppler flowmeter; NTS, nucleus tractus solitarius; Vsp, trigeminal spinal nucleus; V, trigeminal nerve root; VII, facial nerve root. (B) Typical examples of the blood flow recordings demonstrating the inhibitory effects of isoflurane at concentrations of 1.0% (i) or 2.0% (ii)] on the blood flow (BF) in the SMG (in arbitrary units, a.u.) elicited by electrical stimulation of the central cut end of the lingual nerve (LN; open circles) or the peripheral cut end of the chorda-lingual nerve (CLN; filled circles), and the systemic arterial blood pressure (SABP; shown in mm Hg). The parameters for the electrical stimulation of either the LN or CLN were 20 V, 10 Hz, 2-ms pulse duration for 20 sec. Abscissa: time (min). Arrows indicate the duration of isoflurane inhalation (30 min).

View larger version (24K): [in this window] [in a new window]   Figure 2. Time-course of the concentration-related effects of isoflurane with and without the continuous administration of methoxamine on blood flow increases in the SMG elicited by electrical stimulation of either the central cut end of the lingual nerve (LN) or the peripheral cut end of the chorda-lingual nerve (CLN). (A) LN without methoxamine; (B) CLN without methoxamine; (C) LN with methoxamine; (D) CLN with methoxamine. Electrical stimulation of LN was at supramaximal intensity (20 V, 10 Hz, 2-ms pulse duration) for 20 sec. The inhaled concentration of isoflurane was 1.0% (open and filled circles), 1.5% (open and filled triangles), or 2.0% (open and filled squares). Abscissa: time (min) after the start of isoflurane inhalation. Each value is expressed as a percentage of the pre-treatment blood flow increase (at time 0) elicited by stimulation of the LN or CLN, and is given as mean ± SE. Statistical significance from control (at time 0) was assessed by ANOVA followed by a contrast test (*P < 0.05, **P < 0.01, ***P < 0.001). Number of animals used is shown in parentheses.

View larger version (13K): [in this window] [in a new window]   Figure 3. The concentration-related effects of isoflurane with or without continuous administration of methoxamine on mean arterial blood pressure (MAP). Hatched and open bars indicate MAP with or without the administration of methoxamine throughout the inhalation of isoflurane. Changes in MAP during isoflurane inhalation (for 30 min) are expressed as mean ± SE (mm Hg). Statistical significance from control (at time 0) was assessed by ANOVA followed by a contrast test (*P < 0.05, **P < 0.01, ***P < 0.001). Asterisks (*P < 0.05, ***P < 0.001) indicate significant differences between measurements with and those without methoxamine at the same concentration of isoflurane (unpaired t test). Number of animals used is shown in parentheses.

View larger version (17K): [in this window] [in a new window]   Figure 4. Effects of methoxamine and the GABA antagonist picrotoxin (2 mg/kg iv) on isoflurane (2%)-induced inhibition of either the blood flow increase in the SMG (SMGBF) elicited by electrical stimulation (20 V, 10 Hz, 2-ms pulse duration for 20 sec) of the peripheral cut end of the chorda-lingual nerve (CLN; A), or the change in mean arterial blood pressure (MAP; B). Each of opened, hatched, and gray bars indicates the SMGBF under isoflurane inhalation (for 30 min) without any administration, with continuous administration of methoxamine, and with prior administration of picrotoxin. Vasodilator response elicited by electrical stimulation of CLN during isoflurane inhalation (for 30 min) is expressed as a percentage of the pre-isoflurane response and is given as mean ± SE. Changes in MAP during isoflurane inhalation (for 30 min) are expressed as mean ± SE (mm Hg). Statistical significance of differences from control (at time 0) was assessed by means of ANOVA, followed by a contrast test (*P < 0.05, **P < 0.01, ***P < 0.001). Brackets (P < 0.05, P < 0.001) indicate significant difference between 2 columns (unpaired t test). Number of animals used is shown in parentheses.

Journal of Dental Research, Vol. 85, No. 4, 379-383 (2006)
DOI: 10.1177/154405910608500419


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