domoic-acid and 3-5-dihydroxyphenylglycine

The effects of a novel vasopressin fragment analog NC-1900 (pGlu-Asn-Ser-Pro-Arg-Gly-NH2 acetate) were studied on learning and/or memory impairment in passive avoidance task and on cell damage of cultured cerebro-cortical neurocytes induced by glutamic acid. A small dose of NC-1900 (1 ng/kg, s.c.) ameliorated impairments of learning and/or memory induced by intracisternal injection of 467.6 micrograms of 10 microliters glutamic acid. NC-1900 also ameliorated the impairments induced by intracisternal NMDA, AMPA-antagonist CNQX and by metabotropic receptor (mGluR1) agonist 3,5-dihydroxyphenylglycine but not by kainate agonist domoic acid nor MK-801 in mice. NC-1900 (100 pM, 1nM) ameliorated the cell damage of cultured rat cerebro-cortical neurocytes induced by 100 and 1000 microM of glutamic acid. These results suggest that NC-1900 may serve as a remedies in various patients with certain brain disorders induced by excess glutamic acid.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Arginine Vasopressin; Avoidance Learning; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Glutamic Acid; Glycine; Kainic Acid; Learning Disabilities; Male; Memory Disorders; Mice; Mice, Inbred Strains; N-Methylaspartate; Neuromuscular Depolarizing Agents; Oligopeptides; Pyrrolidonecarboxylic Acid; Rats; Rats, Sprague-Dawley; Resorcinols

The effect of acute ethanol on Ca2+ signals evoked by ionotropic (iGluR) and metabotropic (mGluR) glutamate receptor (GluR) activation and K+ depolarization was examined in cultured rat cerebellar Purkinje neurons to assess the ethanol sensitivity of these Ca2+ signaling pathways. Mature Purkinje neurons approximately 3 weeks in vitro were studied. iGluRs were activated by (RS)-alpha-amino-3-hydroxyl-5 methyl-4-isoxazolepropionic acid (AMPA; 1 and 5 microM) and domoate (5 microM). mGluRs were activated by (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD; 300 microM) and (R,S)-3,5-dihydroxyphenylglycine (DHPG; 200 microM). These agents and K+ (150 mM) were applied from micropipettes by brief (1 s) microperfusion pulses. Ca2+ levels were monitored at 2-3 s intervals during pre- and post-stimulus periods using microscopic digital imaging and the Ca2+ sensitive dye fura-2. iGluR and mGluR agonists and K+ produced abrupt increases in intracellular Ca2+ that slowly recovered to baseline resting levels. Acute exposure to ethanol at 33 mM (150 mg%) and 66 mM (300 mg%) significantly reduced the amplitude of the Ca2+ signals to iGluR agonists and K+ with little or no effect on Ca2+ signals to mGluR agonists. In contrast, acute ethanol at 10 mM (45 mg%) had no effect on the Ca2+ signals to the iGluR agonist AMPA but significantly enhanced the Ca2+ signals to the mGluR agonist DHPG. These results show that ethanol modulates Ca2+ signaling linked to GluR activation in a receptor subtype specific manner, and suggest that Ca2+ signaling pathways linked to GluR activation and membrane depolarization may be important mechanisms by which ethanol alters the transduction of excitatory synaptic signals at glutamatergic synapses and thereby affects intercellular and intracellular communication in the CNS.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Calcium; Cells, Cultured; Cerebellar Cortex; Cycloleucine; Embryo, Mammalian; Ethanol; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Glycine; Kainic Acid; Membrane Potentials; Potassium; Purkinje Cells; Rats; Receptors, Glutamate; Receptors, Metabotropic Glutamate; Resorcinols