Abstract
Effects of serotonin one neuromuscular transmission and muscle contraction were studied in the tibialis anterior of rabbits. Serotonin antagonised the Mg++-induced block of transmission, and also provided dual effects on the curare-induced block, anti-curare phase followed by curare-potentiating phase. Independent of transmission processes, serotonin caused a reduction in twitch tension, mainly associated with decreased acceleration of twitch development. These serotonin actions were independent of vascular changes; pharmacological mechanisms are discussed in comparison with those of adrenaline and isoprenaline. A possible role of serotonin in causing a myopathy is proposed.