Electrophysiological and pharmacological actions of N-acetylaspartylglutamate intracellularly studied in cultured chick cerebellar neurons.

The electrophysiological and pharmacological actions of N-acetylaspartylglutamate (NAAG) in cultured chick cerebellar neurons were intracellularly investigated in comparison with L-aspartate (ASP) and L-glutamate (GLU). Iontophoretically applied NAAG dose-dependently induced depolarizations associated with increases in spike discharge and changes in membrane conductance. Relative excitatory potencies seemed to be GLU greater than ASP greater than or equal to NAAG. The voltage-dependent increase in input resistance observable in the presence of Mg ions was most notable for ASP, moderate for NAAG and least for GLU. The reversal potential of NAAG-induced depolarization was at about 0 mV and similar to that for ASP or GLU, indicating primary concern of Na+/K+-conductances to the NAAG action. Mg ions depressed the actions of ASP and NAAG more strongly than the GLU action. 2-Amino-5-phosphonovalerate (APV) and D-alpha-aminoadipate antagonized the actions of ASP and NAAG more effectively than the GLU action. 2-Amino-4-phosphonobutyrate (APB) and glutamic acid diethylester showed rather non-selective antagonisms to NAAG, ASP and GLU. These results suggest that NAAG is excitatory to cultured chick cerebellar neurons and functionally resembles ASP or is intermediate between ASP and GLU, and may also support the suggested candidacy of NAAG for a neurotransmitter in the CNS.