Analgesic effects of amiodarone in mouse models of pain

Figures

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  Figure 1. Analgesic responses induced by amiodarone. (A) Acetic acid-induced writhing test. At doses of 50 mg/kg and higher, amiodarone significantly reduced nociceptive responses in a dose-dependent manner. (B) Formalin test, phase I. At doses of 100 and 200 mg/kg, amiodarone significantly reduced nociceptive response. (C) Formalin test, phase II. At doses of 100 and 200 mg/kg, amiodarone significantly reduced nociceptive response. (D) Tail withdrawal test. At doses of 100 and 200 mg/kg, amiodarone significantly increased the withdrawal latency. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001. Abbreviation: AMD, amiodarone.

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  Figure 2. Effects of amiodarone on hemodynamic status and spontaneous activity. (A) Heart rate 1 h after administration of either normal saline (control group) or amiodarone (amiodarone groups). (B) Mean blood pressure 1 h after the administration of either normal saline (control group) or amiodarone (amiodarone groups). (C) Number of squares crossed during the open-field test. *p<0.05, **p<0.01. Abbreviation: AMD, amiodarone.

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  Figure 3. Effects of each selective agonist on analgesic responses induced by amiodarone during the acetic acid-induced writhing test. (A) Veratrine, a voltage-gated sodium channel opener. (B) BAYK8644, an L-type calcium channel opener. (C) NS1643, voltage-gated potassium channel (Kv 11.1) opener. (D) Isoproterenol, a β-adrenergic receptor agonist. The analgesic effects of amiodarone (100 mg/kg) were abolished by veratrine but not by BAYK8644, NS1643, or isoproterenol. When administered alone, veratrine, BAYK8644, NS1643, and isoproterenol did not affect nociceptive responses in the writhing test. *p<0.05, **p<0.01, ***p<0.001 compared with the control group. †p<0.05, ††p<0.01, †††p<0.001, ††††p<0.0001 compared with the amiodarone alone group. Abbreviations: N, NS1643; A, amiodarone; V, veratrine; B, BAYK8644; I, isoproterenol.

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  Figure 4. Effects of veratrine on analgesic responses induced by amiodarone during the formalin test and tail withdrawal test. (A) Formalin test, phase I. (B) Formalin test, phase II. (C) Tail withdrawal test at 55 °C. Veratrine 2 mg/kg reversed the antinociceptive effects of amiodarone in the formalin test and tail withdrawal test. *p<0.05 . Abbreviations: A, amiodarone; V, veratrine.