Neuropeptide Y (NPY) (13-36) is a C-terminal fragment of NPY, a neuropeptide involved in controlling appetite, blood pressure, cardiac contractility, and intestinal secretion. NPY (13-36) is an agonist of the NPY receptor Y2 with Ki values of 1.28 and 2.62 nM for the rat recombinant receptor in CHO cells and in rat jejunal crypt cell membranes, respectively. It inhibits forskolin-induced cAMP accumulation with EC50 values of 300, 2.2, >1,000, and 20 at Y1, Y2, Y4, and Y5 receptors, respectively, in vitro. NPY (13-36) inhibits basal short circuit currents (EC50 = ~2 µM) and electrical field stimulated-secretory responses in isolated rat jejunal mucosa (EC50 = ~200 nM) but does so less potently than NPY . NPY (13-36) also reduces the frequency of spontaneous excitatory postsynaptic currents (EPSCs) in the CA3 region of hippocampal slices from wild-type but not Y5 receptor knockout mice.