 Neurotensin-deficient mice display defects in responses to several antipsychotic drugs consistent with the idea that neurotensin signaling is a key component underlying at least some antipsychotic drug actions.These mice exhibit modest defects in prepulse inhibition (PPI) of the startle reflex, a model that has been widely used to investigate antipsychotic drug action in animals.Antipsychotic drug administration augments PPI under certain conditions.