Decrease of effectivity of 'competing' synaptic input requires protein synthesis

We describe that tetanus-induced long-term increase of the response amplitu de in one input to an identified neuron is accompanied by a decrease, of sy naptic responses in another, non-tetanized input. Induction of the decrease of responses in non-tetanized inputs was prevented by bath application of protein synthesis blockers (anisomycin or cycloheximide). The decrease of r esponses also did not occur in experiments when tetanization was substitute d by short-term serotonin applications or extracellular stimulation of sero tonergic cells known to potentiate investigated synaptic inputs. The result s suggest that the heterosynaptically evoked decrease of synaptic response amplitude may be due to involvement of postsynaptic protein synthesis-depen dent mechanisms. (C) 2001 Elsevier Science B.V. All rights reserved.