Neurotensin is a 13 amino acid peptide that induces hypothermia and mediates analgesia when administered centrally, and also mediates the behavioral effects of antipsychotic drugs in rodents. In addition, several intestinal functions, such as contractility and inflammation, are mediated by neurotensin. The actions of neurotensin are mediated by two GPCRs, NTR1 (or NTS1) and NTR2 (or NTS2). NTR1 knockout mice are resistant to the hypothermic, analgesic and contractile effects of neurotensin, indicating that NTR1 is the primary mediator of these effects. Small molecule antagonists, including SR48692 and SR142948A, that are partially selective for NTR1 also interfere with the biological effects of neurotensin.