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THE FREE AMINO ACIDS IN PERIPHERAL NERVES AND IN ISOLATED INHIBITORY AND EXCITATORY NERVE FIBRES OF CANCER MAGISTER 1
Author(s) -
Sorenson Martha M.
Publication year - 1973
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1973.tb00092.x
Subject(s) - inhibitory postsynaptic potential , excitatory postsynaptic potential , axoplasm , amino acid , glutamate receptor , chemistry , biophysics , biochemistry , anatomy , axon , biology , endocrinology , receptor
— Free amino acids in whole nerve and in excitatory and inhibitory fibres isolated from the walking legs of the crab, Cancer mgister , have been determined, using a densitometric method which permits quantitative estimates of 1 nmol of a ninhydrin‐positive substance on paper chromatograms. In confirmation of previous reports, whole nerve contained 5 amino acids at levels greater than 10 mmol/kg wet wt., including two anions (glutamate and aspartate) of major importance. The concentrations of 12 other amino acids were also estimated. The free amino acid fraction contributed about 40% (415 mosmol/kg of cell water) to the osmotic concentration of the tissue. Isolated inhibitory fibres were distinguished by a 15‐fold higher level of GABA than that found in excitatory fibres (46 vs 3·1 mmol/l. of axoplasm). The level of proline also differed in the two types of fibres, but in contrast to GABA it was less concentrated in inhibitory fibres. As a consequence of these and of other smaller differences, the total concentration of free amino acids was slightly less in inhibitory fibres (365 vs 405 mmol/l. of axoplasm in excitatory fibres). The demonstration of the presence of GABA in crab inhibitory axons supports earlier suggestions that it may be the inhibitory transmitter at crab neuromuscular junctions.