Background: Acid-sensing ion channels (ASICs) have a significant role in the sensation of pain and constitute an\r\nimportant target for the search of new antinociceptive drugs. In this work we studied the antinociceptive\r\nproperties of the BM-21 extract, obtained from the sea grass Thalassia testudinum, in chemical and thermal models\r\nof nociception in mice. The action of the BM-21 extract and the major phenolic component isolated from this\r\nextract, a sulphated flavone glycoside named thalassiolin B, was studied in the chemical nociception test and in\r\nthe ASIC currents of the dorsal root ganglion (DRG) neurons obtained from Wistar rats.\r\nResults: Behavioral antinociceptive experiments were made on male OF-1 mice. Single oral administration of\r\nBM-21 produced a significant inhibition of chemical nociception caused by acetic acid and formalin (specifically\r\nduring its second phase), and increased the reaction time in the hot plate test. Thalassiolin B reduced the licking\r\nbehavior during both the phasic and tonic phases in the formalin test. It was also found that BM-21 and thalassiolin B\r\nselectively inhibited the fast desensitizing (t < 400 ms) ASIC currents in DRG neurons obtained from Wistar rats, with\r\na nonsignificant action on ASIC currents with a slow desensitizing time-course. The action of thalassiolin B shows no\r\npH or voltage dependence nor is it modified by steady-state ASIC desensitization or voltage. The high concentration\r\nof thalassiolin B in the extract may account for the antinociceptive action of BM-21.\r\nConclusions: To our knowledge, this is the first report of an ASIC-current inhibitor derived of a marine-plant\r\nextract, and in a phenolic compound. The antinociceptive effects of BM-21 and thalassiolin B may be partially\r\nbecause of this action on the ASICs. That the active components of the extract are able to cross the blood-brain\r\nbarrier gives them an additional advantage for future uses as tools to study pain mechanisms with a potential\r\ntherapeutic application.
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