Svend Treppendahl

(S)‐Carboxy‐3‐Hydroxyphenylglycine, an Antagonist of Metabotropic Glutamate Receptor (mGluR)1a and an Agonist of mGluR2, Protects Against Audiogenic Seizures in DBA/2 Mice

Abstract: The in vivo anticonvulsant effects and in vitro metabo‐tropic glutamate receptor selectivity of (S)‐4‐carboxy‐3‐hydroxy‐phenylglycine [(S)‐4C3HPG] were examined. Intracerebroventricular injection of (S)‐4C3HPG dose‐dependently antagonized audiogenic‐induced clonic and tonic convulsions in DBA/2 mice with ED60 values of 76 and 110‐nmol per mouse, respectively. (S)‐4C3HPG dose‐dependently inhibited the spontaneously evoked epileptic spikes in a cingulate cortex‐corpus callosum slice preparation. (SJ‐4C3HPG displaced the binding of [3H]glutamate in membranes prepared from baby hamster kidney (BHK) cells expressing the metabotropic glutamate receptor mGluR1a with an EC50 of 5 β 1 uM. (S)‐4C3HPG dose‐dependently antagonized glutamate‐stimulated phosphoinositide hydrolysis in BHK cells expressing mGluR 1a with an IC50 of 15 β 3 μM. (S)‐4C3HPG was, however, an agonist at mGluR2 with an EC60 of 21 β 4 μM for inhibition of forskolin‐stimulated cyclic AMP formation in BHK cells expressing the mGluR2. (S)‐4C3HPG had no effects at mGluR4a. These data suggest that the anticonvulsant action of (S)‐4C3HPG is mediated by combined antagonism of mGluRIa and agonism of mGluR2. These results suggest the importance of mGluR1a and/or mGluR2 in the control of epileptic activity.

Synthesis and structural determination of stereoisomers of muscarinic ligands of the (3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicycloalkane type

Methods for the synthesis of each of the four stereoisomers of 6-(3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[3.2.1]oc tane (10, 11, 12, and 13) and 3-(3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[2.2.1]he ptane (18, 19, 20, and 21), and the two stereoisomers of 3-(3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[2.2.2]oc tane (27 and 28) were developed. The relative configuration of the compounds was determined on the basis of previously described 1H NOE experiments, and the absolute configuration of 6-(3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[3.2.1]oc tanes (10, 11, 12, and 13) and 3-(3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[2.2.2]oc tane (27 and 28) was determined by single crystal X-ray crystallography. Optical purity was determined by capillary electrophoresis (CE) using chiral selectors as trimethyl-beta-cyclodextrin and heparin dissolved in the running buffer. All the 3-(3-propylthio-1,2,5-thiadiazol-4-yl)-1-azabicycles had low nanomolar affinity for muscarinic receptors as determined by displacement of radiolabelled oxotremorine-M (3H-Oxo-M) and pirenzepine (3H-Pz) from cortical rat brain homogenates. The binding assay discriminated between diastereomers, but only a minor degree of enantioselectivity was observed in the binding assays.