CURRENT KNOWLEDGE OF THE STORAGE AND RELEASE OF TRANSMITTER CANDIDATE AMINO ACIDS AND NEUROPEPTIDES

Publisher Summary This chapter discusses storage and release of transmitter candidate amino acids and neuropeptides. For a substance to be considered as a candidate to be a neurotransmitter, it should be stored and released from the presynaptic neuron and show an identity of action with the natural transmitter released by the bstimulation of the presynaptic pathway. The evidence in favor of several amino acids as major neurotransmitters in the mammalian central nervous system (CNS) is now very extensive. The available evidence suggests that glutamic acid (and possibly also aspartic acid) may be the transmitter of a number of neo- and allocortical neurons, while GABA and glycine are candidates for inhibitory transmitters, GABA in neurons throughout the neuroaxis and glycine particularly in the spinal cord. In the case of glutamic acid, aspartic acid, and glycine, these amino acids are involved in general intermediary metabolism so that the recognition of a specific transmitter pool of amino acid may be difficult. For GABA, the situation is simplified as the amino acid is made from glutamic acid by a specific glutamate decarboxylase whose activity is concentrated in GABAergic neurons.