Levels of free amino acids in excitatory, inhibitory and sensory axons of the walking limbs of the lobster

Using a gas chromatography procedure, the levels of several amino acids were determined in individual excitatory and inhibitory axons, in bundles of sensory fibers, and in muscle tissue from the walking limb of the lobster, $\text{Homarus}$$\text{americanus}$. In addition, the levels of amino acids in the hemolymph were also determined. Of the amino acids assayed in the excitatory and inhibitory axons and in the sensory fibers the level of aspartate was highest whereas in hemolymph and muscle, aspartate had one of the lowest values. The levels of glutamate, glycine and proline were significantly higher in the excitatory axons than in the inhibitory axons. GABA was present in inhibitor axons and in the muscle tissue which these axons innervate and was not detected in the other axons assayed nor in the hemolymph. β-Alanine was present at low levels in hemolymph and in muscle but was not detected in the excitatory nor in the inhibitory axons.