Increase of serotonin in plasma during onset of halothane-induced malignant hyperthermia in pigs.

The levels of serotonin (5-HT) were determined in platelet-free and platelet-rich plasma before and during the onset of halothane-induced malignant hyperthermia (MH) in genetically MH-susceptible pigs. During MH onset, the free (i.e. physiologically active) levels of 5-HT in plasma rose concomitantly with the increases in muscle tone, body temperature, venous pCO2 and plasma lactate. Since pharmacological stimulation of 5-HT2 receptors has recently been shown to trigger MH in susceptible pigs, the finding of increased 5-HT plasma levels during onset of halothane-induced MH may indicate that 5-HT is involved in the mechanisms by which volatile anesthetics trigger this myopathic syndrome.