negatively regulates negative regulation of biological process excitatory postsynaptic potential biological regulation negative regulation of excitatory postsynaptic potential GO:0090394 Any process that prevents the establishment or decreases the extent of the excitatory postsynaptic potential (EPSP) which is a temporary increase in postsynaptic potential due to the flow of positively charged ions into the postsynaptic cell. The flow of ions that causes an EPSP is an excitatory postsynaptic current (EPSC) and makes it easier for the neuron to fire an action potential. 2010-12-15T01:43:12Z negative regulation of EPSP reduction of excitatory postsynaptic membrane potential negative regulation of excitatory post-synaptic membrane potential modulation of excitatory postsynaptic potential