Magnesium selectively inhibits N-methyl-aspartic acid-induced hypermotility after intra-accumbens injection.

The excitatory amino acids, N-methyl-aspartic acid, kainic acid and quisqualic acid have been shown to produce a marked increase in locomotor activity after bilateral injection into the rat nucleus accumbens. The intra-accumbens injection of magnesium inhibited the hypermotility response produced by N-methyl-aspartic acid in a dose-dependent manner. However, magnesium had no significant inhibitory effect on the increase in motility produced by either kainic acid or quisqualic acid. In contrast to magnesium, calcium produced a weak inhibitory action on N-methyl-aspartic acid-induced hypermotility. These data suggest that in the nucleus accumbens, at least two receptor types (N-methyl-aspartic acid/magnesium-sensitive and non-N-methyl-aspartic acid/magnesium-insensitive receptors) are present which can mediate the stimulation of locomotor activity produced by excitatory amino acids.