Abstract <p>Atony and atrophy of mammalian postural muscles can resultfrom mechanical unloading (weightlessness, hypokinesia). There isreason to believe that calcium-permeable mechanosensitive channelsmay contribute to the development of muscle atrophy caused by mechanicalunloading. The aim of the study was to assess time course changesin the expression of key mechanosensitive channels in rat soleusmuscle under conditions of mechanical unloading. Male Wistar ratswere exposed to hindlimb suspension (HS) for 1, 3, 7 and 14 days.The expression of Piezo1, TRPC1, TRPC3, TRPC6, TRPM3, TRPM7 andTMEM63B mRNA was determined using PCR. Piezo1 protein content wasassessed by Western blotting. Piezo1 mRNA expression transientlyincreased after 24 h of HS, but did not differ from the controlafter 3, 7 and 14 days of unloading. A decrease in Piezo1 proteincontent was observed after 3, 7 and 14 days of HS relative to thecontrol. At the early stages of HS, there was a significant increasein the mRNA expression of TRPC3, TRPM3, TRPM7 and TMEM63B, whileTRPC6 expression was reduced. The level of TRPC1 mRNA expressionwas increased only after 3 days of HS. Seven-day unloading did notcause changes in mRNA expression of TRPC1, TRPC3, TRPM3 and TMEM63B,but led to increased TRPM7 expression. After two weeks of HS, thesoleus muscle exhibited a decrease in mRNA expression of TRPC1,TRPC6, TRPM3 and TMEM63B. Thus, at an early stage of mechanical unloading(1 and 3 days), there occurs a transient increase in mRNA expressionof Piezo1, TRPC1, TRPC3 and TMEM63B, but at a later stage of unloading(14 days), the expression of TRPC1, TRPC6, TRPM3, TMEM63B at themRNA level and Piezo1 at the protein level decreases.</p>