Potent and specific action of the mGlu1 antagonists YM-298198 and JNJ16259685 on synaptic transmission in rat cerebellar slices.
OBJECTIVE
Specific and selective inhibitors for mGlu1 receptors are presently inadequate. A new generation of non-competitive mGlu1 antagonists with low nanomolar potencies is emerging. We evaluated two new compounds, YM-298198 and JNJ16259685, for effectiveness, potency and specificity for the first time in a brain slice preparation.


METHODS
Patch-clamp recording of Purkinje neurones in cerebellar slices were obtained. The slow mGlu1-mediated EPSP was used to establish a concentration-response curve. Fast excitatory synaptic inputs were tested for non-specific effects.


RESULTS
YM-298198 and JNJ16259685 inhibited the synaptic activation of mGlu1 in a concentration-dependent manner (IC(50) values of 24 nM and 19 nM, respectively). The antagonists were slow to inhibit and to reverse on washout, probably due to their lipophilic nature. There were no non-specific effects on fast AMPA receptor-mediated synaptic transmission in the cerebellum.


CONCLUSIONS
These compounds are more than a thousand-fold more potent than previously available compounds. Their selectivity and specificity will be very useful for studying the role of mGlu1 receptors both in vitro and in vivo.
Fukunaga
I
I
Department of Physiology, University College London, Gower Street, London, UK.
Yeo
C H
CH
Batchelor
A M
AM
D000818:Animals; D001562:Benzimidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials; D057927:Hydrophobic and Hydrophilic Interactions; D066298:In Vitro Techniques; D020128:Inhibitory Concentration 50; D011689:Purkinje Cells / Q000187:drug effects* / Q000502:physiology; D011804:Quinolines / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors*; D009435:Synaptic Transmission / Q000187:drug effects*; D013844:Thiazoles / Q000008:administration & dosage / Q000494:pharmacology*
C495417:(3,4-dihydro-2H-pyrano(2,3)b-quinolin-7-yl)-(cis-4-methoxycyclohexyl) methanone; C505455:6-amino-N-cyclohexyl-N,3-dimethylthiazolo(3,2-a)benzimidazole-2-carboxamide; D001562:Benzimidazoles; D011804:Quinolines; D018091:Receptors, AMPA; D018094:Receptors, Metabotropic Glutamate; D013844:Thiazoles; C104077:metabotropic glutamate receptor type 1