Multiple G-protein-coupled receptors mediate presynaptic inhibition at single excitatory synapses in the rat visual cortex

Modulation of excitatory synaptic transmission by agonists for several neur otransmitter receptors was investigated at intrinsic cortical synapses deri ved from single presynaptic neurons. Excitatory postsynaptic currents (EPSC s) were recorded from layer 5 pyramidal neurons in the rat visual cortex in response to minimal stimulation within the same layer. 5-hydroxytryptamine , adenosine, baclofen, carbachol and DCG-IV all suppressed EPSCs with an in crease in paired-pulse ratio. These agonists reduced the frequency of minia ture EPSCs without significantly affecting their amplitude distribution. Th ese results suggest that glutamatergic excitatory transmission in the neoco rtex is under the control of presynaptic inhibition mediated by multiple ne uromodulator receptors co-expressed in single presynaptic terminals. (C) 20 01 Elsevier Science Ireland Ltd. All rights reserved.