Crossed antagonism between muscarinic and group I mGlu receptors. A, LTP induced by OxoM (5 μm; gray circles) coupled to a postsynaptic hyperpolarization, was suppressed by the mGluR1/5 antagonists MPEP and LY367385 (red circles). Top, Schematic showing the arrangement of stimulating and recording electrodes. Inset, Representative sample traces from a single neuron before (black) and after (red) the pharmacological activation of the mAChR paired with a postsynaptic hyperpolarization. B, The LTP induced by coupling postsynaptic hyperpolarization and the type I mGluR agonist, DHPG (gray circles), was suppressed by the application of the mAChR antagonist telenzepine (75 nm; blue circles). Inset, Representative sample traces from a single neuron before (black) and after (red) the pharmacological activation of the mGluR paired with a postsynaptic hyperpolarization. Symbols in A and B represent an average of EPSP slope from 20 events elicited at 15 s intervals and the bars show SEM. Time t = 0 corresponds to the induction procedure.