Effects of metabotropic glutamate receptor agonists on excitatory and inhibitory transmissions in cultured rat hippocampal neurons.

Effects of the metabotropic glutamate receptor agonist, trans-ACPD (tACPD), on the excitatory and the inhibitory transmissions were examined with cultured rat hippocampal neurons, by recording monosynaptic excitatory (EPSCs) and inhibitory postsynaptic currents (IPSCs) evoked by electrical stimulation of single presynaptic neurons. EPSCs were suppressed reversibly by application of 100 microM tACPD in almost all the tested neuron pairs with excitatory connections. Effects of tACPD on IPSCs were variable. Application of tACPD did not affect IPSCs in 15 pairs, suppressed them in eight pairs and enhanced them in the remaining eight pairs out of 31 neuron pairs with inhibitory connections. The study demonstrated that in the hippocampus the activation of metabotropic glutamate receptors modulated the inhibitory transmission differently at different synapses, whereas it always suppressed the excitatory transmission.