Volume 17, Issue 39, January - June, 2023

The effect of the imidazoline receptor agonist rilmenidine on visceral and thermal nociceptive pain in mice

Omar ME Abdel-Salam^1♦, Amany A Sleem²

¹Department of Toxicology and Narcotics, Medical Research and Clinical Studies Institute, National Research Centre, Cairo, Egypt
²Department of Pharmacology, Medical Research and Clinical Studies Institute, National Research Centre, Cairo, Egypt

^♦Corresponding author
Department of Toxicology and Narcotics, Medical Research and Clinical Studies Institute, National Research Centre, Dokki, Cairo, Egypt

ABSTRACT

The effect of the centrally acting imidazoline agonist rilmenidine was examined in acute visceral and thermal nociceptive pain models, Porsolt's forced swimming test and rotarod test in mice. Rilmenidine given intraperitoneally (i.p.) at doses of 0.25, 0.5, 1, 2 or 4 mg/kg dose-dependently inhibited the development of abdominal constrictions evoked by i.p. injection of dilute acetic acid, reducing the number of writhes by 38.4-99.8%. The antinociceptive effect of rilmenidine (1 mg/kg, i.p.) was reduced by atropine, the non-selective beta-adrenoceptor blocker propranolol, the a-2 adrenoceptor antagonist yohimbine and the ATP-sensitive potassium channel blocker glibenclamide. The antinociception caused by rilmenidine was enhanced by the a1-adrenoceptor antagonist prazosin and the sympathetic blocker guanithidine. The drug at the dose of 1 or 2 mg/kg produced significant increases in response latencies in the hot plate test. Rilmenidine (0.5-2 mg/kg, i.p.) did not alter the immobility time in the Porsolt's forced-swimming test or time spent on rotarod testing. The number of spontaneous movements was not significantly affected by rilmenidine at 0.5, 1 or 2 mg/kg, i.p. These results indicate that rilmenidine exerts antinociceptive action in thermal and visceral inflammatory pain models in mice. The visceral pain inhibitory action of rilmenidine may involve ß-adrenergic, cholinergic and KATP channels.

Keywords: Rilmenidine, imidazoline receptors, visceral pain, thermal pain, hotplate, writhing

Drug Discovery, 2023, 17(39), e1dd1001

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DOI: https://doi.org/10.54905/disssi.v17i39.e1dd1001

Published: 12 January 2023