Excitatory Amino Acid Receptors

Abstract

The potent neuroexcitatory effects of acidic amino acids were first described over 25 years ago (Hayashi, 1954). In the interim, through the sustained efforts of several neurophysiologic laboratories, evidence has accrued that glutamic acid and possibly aspartic acid may serve as excitatory neurotransmitters in the mammalian central nervous system (Curtis et al., 1972; Curtis and Johnston, 1974; Krnjevic, 1974; McLennan, 1975). Prompted by these neurophysiologic observations, neurochemists over the last several years have attempted to identify neuronal pathways in the mammalian CNS that may utilize the acidic amino acids as their neurotransmitters; and neuropharmacologists have begun to explore interactions between drugs and the excitatory amino acids. An overview of this research suggests that the excitatory amino acids may play a fundamental role in brain function that is only beginning to gain wide appreciation. Thus, circumstantial evidence has implicated L-glutamic acid as the neurotransmitter for cortical pyramidal cells (Divak et al., 1977; Lund-Karlsen and Fonnum, 1978), cerebellar granule cells (Young et al., 1974) and primary sensory afferents (Johnson, 1972), in the mechanisms of action of sedatives and anticonvulsants (Richards and Smaje, 1976; MacDonald and Barker, 1979), and in the pathophysiology of certain neurodegenerative disorders (Perry et al., 1977; Coyle, 1979).