title: Differential effects of (D)- and (L)-homocysteic acid on the membrane potential of cat caudate neurons in situ.
abstract: The enantiomers of homocysteic acid have been applied by microiontophoresis to neurons of the cat caudate nucleus in situ. The (L)-enantiomer elicited a bursty firing pattern similar to the one caused by N-methyl-D-aspartate, but differing from the N-methyl-D-aspartate pattern inasmuch as (L)-homocysteate induced depolarization shifts were shorter and had a smaller amplitude. (L)-Homocysteate induced excitations could be strongly inhibited by the selective N-methyl-D-aspartate antagonist 2-amino-7-phosphonoheptanoic acid but they were less sensitive to this antagonist than N-methyl-D-aspartate itself. (D)-Homocysteate elicited a more regular firing pattern similar to the one caused by non-N-methyl-D-aspartate excitatory amino acids such as quisqualate. These excitations were only rarely inhibited by 2-amino-7-phosphonoheptanoic acid. Our results suggest that (L)-homocysteate, a transmitter candidate at central mammalian synapses, is a mixed excitatory amino acid agonist with a strong preference for N-methyl-D-aspartate receptors in the cat caudate nucleus, while (D)-homocysteate has a predominant action at non-N-methyl-D-aspartate excitatory amino acid receptors.
authors.affiliation: Sandoz Research Institute, Berne, Switzerland.
authors.forename: P L
authors.initials: PL
authors.lastname: Herrling
authors.forename: J
authors.initials: J
authors.lastname: Maeder
authors.forename: C L
authors.initials: CL
authors.lastname: Meier
authors.forename: K Q
authors.initials: KQ
authors.lastname: Do
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000031:analogs & derivatives*; D000200:Action Potentials / Q000187:drug effects; D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D002415:Cats; D002421:Caudate Nucleus / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology*; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D006710:Homocysteine; C007956:homocysteic acid; D015763:2-Amino-5-phosphonovalerate; C031231:2-amino-7-phosphonoheptanoic acid