L-homocysteic acid but not L-glutamate is an endogenous N-methyl-D-aspartic acid receptor preferring agonist in rat neocortical neurons in vitro.
The effects of ionophoretically applied L-homocysteate (L-HCA), L-glutamate (L-Glu) and N-methyl-D-aspartate (NMDA) were compared in rat neocortical neurons recorded intracellularly in vitro. The firing pattern and the time course of membrane depolarization induced by L-HCA resembled those of NMDA responses. Action potentials evoked by NMDA and L-HCA were superimposed upon slow depolarizations in a burst-like pattern, while L-Glu elicited single spike discharges. Ionophoretically applied D-2-amino-5-phosphonovalerate (2-APV) at doses sufficient to abolish NMDA responses, markedly reduced the L-HCA induced depolarizations but had no detectable effect on the L-Glu responses. The present findings are consistent with a possible role of L-HCA as an NMDA receptor preferring neurotransmitter in the rat frontal cortex.
D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology*; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D016202:N-Methylaspartate; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000502:physiology*
D005971:Glutamates; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D006710:Homocysteine; C007956:homocysteic acid; D001224:Aspartic Acid; D018698:Glutamic Acid; D016202:N-Methylaspartate