Activity of 2,3-benzodiazepines at native rat and recombinant human glutamate receptors in vitro : Stereospecificity and selectivity profiles

• Published in: Neuropharmacology 1996-01, Vol.35 (12), p.1689-1702
• Main Authors: BLEAKMAN, D, BALLYK, B. A, LODGE, D, SCHOEPP, D. D, PALMER, A. J, BATH, C. P, SHARPE, E. F, WOOLLEY, M. L, BUFTON, H. R, KAMBOJ, R. K, TARNAWA, I
• Format: Article
• Language: English
• Subjects: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid - pharmacology; Animals; Anti-Anxiety Agents; Benzodiazepines - chemistry; Benzodiazepines - metabolism; Benzodiazepines - pharmacology; Benzothiadiazines - pharmacology; Biological and medical sciences; Cell Line; Cerebellum - physiology; Cerebral Cortex - drug effects; Cerebral Cortex - physiology; Excitatory Amino Acid Antagonists - chemistry; Excitatory Amino Acid Antagonists - metabolism; Excitatory Amino Acid Antagonists - pharmacology; Ganglia, Spinal - physiology; Glutamatergic system (aspartate and other excitatory aminoacids); Humans; Kidney; Medical sciences; Membrane Potentials - drug effects; Molecular Structure; Neurons - drug effects; Neurons - physiology; Neuropharmacology; Neurotransmitters. Neurotransmission. Receptors; Pharmacology. Drug treatments; Purkinje Cells - drug effects; Purkinje Cells - physiology; Rats; Rats, Sprague-Dawley; Receptors, AMPA - biosynthesis; Receptors, AMPA - drug effects; Receptors, AMPA - physiology; Recombinant Proteins - drug effects; Recombinant Proteins - metabolism; Spinal Cord - physiology; Structure-Activity Relationship; Transfection
• ISSN: 0028-3908; 1873-7064
• DOI: 10.1016/s0028-3908(96)00156-6

The activity and selectivity of the glutamate receptor antagonists belonging to the 2,3-benzodiazepine class of compounds have been examined at recombinant human non-NMDA glutamate receptors expressed in HEK293 cells and on native rat NMDA and non-NMDA receptors in vitro. The racemic 2,3-benzodiazepines GYKI52466, LY293606 (GYKI53405) and LY300168 (GYKI53655) inhibited AMPA (10 microM)-mediated responses in recombinant human GluR1 receptors expressed in HEK293 cells with approximate IC50 values of 18 microM, 24 microM and 6 microM, respectively and AMPA (10 microM) responses in recombinant human GluR4 expressing HEK293 cells with approximate IC50 values of 22 microM, 28 microM and 5 microM, respectively. GYKI 52466, LY293606 and LY300168 were non-competitive antagonists of AMPA receptor-mediated responses in acutely isolated rat cerebellar Purkinje neurons with approximate IC50 values of 10 microM, 8 microM and 1.5 microM, respectively. The activity of racemic compounds LY293606 and LY300168 was established to reside in the (-) isomer of each compound. At a concentration of 100 microM, GYKI52466, LY293606 and LY300168 produced < 30% inhibition of kainate-activated currents evoked in HEK293 cells expressing either human homomeric GluR5 or GluR6 receptors or heteromeric GluR6+KA2 kainate receptors. The activity of the 2,3-benzodiazepines at 100 microM was weak at kainate receptors, but was stereoselective. Similar levels of inhibition were observed for kainate-induced currents in dorsal root ganglion neurons. Intact tissue preparations were also used to examine the stereoselective actions of the 2,3-benzodiazepines. In the cortical wedge preparation, the active isomer of LY300168, LY303070, produced a non-competitive antagonism of AMPA-evoked depolarizations with smaller changes in depolarizations induced by kainate and no effect on NMDA-dependent depolarizations. LY303070 was also effective in preventing 30 microM AMPA-induced depolarizations in isolated spinal cord dorsal roots with an approximate IC50 value of 1 microM. Synaptic transmission in the hemisected spinal cord preparation was stereoselectively antagonized by the active isomers of LY300168 and LY293606. In summary, these results indicate that 2,3-benzodiazepines are potent, selective and stereospecific antagonists of the AMPA subtype of the non-NMDA glutamate receptor.