On the role of nitric oxide as a cellular messenger in brain

The characteristics of the high-affinity uptake of [3H]-L-arginine into cerebellar and cortical synaptosomes were investigated. Uptake into cerebellar synaptosomes was often greater than seen in cortical synaptosomes under similar experimental conditions, and this was reflected by a higher Vmax in synaptosomes from this brain region. Uptake into synaptosomes prepared from both brain regions was markedly enhanced by removing extracellular Na+, adn inhibited by high concentrations of extracellular K+. Depolarisation with 4-aminopyridine or veratridine has no effect on uptake. Uptake was also unaffected by hyperpolarisation. The profile of inhibition of arginine uptake by related amino acids was similar to that seen for the y+ carrier, but the other characteristic alluded to above suggest that the carrier is distinct from the classical y+ system. The possible relationship between the carrier and the metabolism of arginine through the nitric oxide [NO] pathway, and the role of NO in the central nervous system is discussed.