Definition for Inhibitory postsynaptic potential (IPSP)
From Biology Forums Dictionary
1) The response from an inhibitory neurotransmitter hyperpolarizing the postsynaptic membrane, which reduces the likelihood of an action potential.
2) An inhibitory postsynaptic potential is a synaptic potential that decreases the chance that a future action potential will occur in a postsynaptic neuron - inhibitory presynaptic neurons release neurotransmitters which then bind to the postsynaptic receptors; this induces a postsynaptic conductance change as ion channels open or close - inhibits the next neuron and is dependent upon amount of binding of inhibitory transmitmitter substance.