DHBP inhibits the calcium release induced by 2 mM caffeine and 2 μg/mL polylysine with an IC ₅₀ value of 5 μg/mL and 4 μg/mL, respectively. DHBP inhibits [ ³ H]-ryanodine binding in a dose-dependent manner with an IC ₅₀ of 2.5 μg/mL and 90-100% inhibition at 20-30 μg/mL. Calcium uptake by SR is inhibited in the presence of caffeine and this inhibition is antagonized by concomitant addition of DHBP. Muscle twitches elicited by direct electrical muscle stimulation and contractions induced by either 10 mM caffeine or 1 fLM ryanodine are blocked by pretreatment with DHBP. DHBP blocks the calcium release from SR by direct interaction with the calcium release channel, also known as the ryanodine receptor.