Effects of valine, leucine, isoleucine, and a balanced amino acid solution on the seizure threshold to picrotoxin in rats.

During infusion of branched-chain amino acids (BCAAs) in humans, changes in ventilatory drive, sleeping pattern, and appetite have been reported. The mechanism by which BCAA exerts their effects on CNS remains unclear. An infusion of a BCAA solution (300 mg/kg) has previously been found to increase the seizure threshold in rats to the proconvulsant drug picrotoxin, an antagonist on the GABA-benzodiazepine receptor complex. In this study, each of the BCAAs given separately (valine, leucine, isoleucine; 300 mg/kg) (n = 10) increased the mean latency time to onset of seizures vs. placebo as an indication of an increased seizure threshold. A balanced amino acid solution (Vamin-Glucose) had no effect on the seizure threshold. Thus, these CNS effects are specific for BCAAs and occur with all three.