Evidence from animal studies has led to the proposal that neuropeptide Y (NPY) has anxiolytic-like effects in rats after intracerebroventricular (i.c.v.) administration. The purpose of the present study was to extend these observations by examining the behavioral effects of a series of NPY receptor agonists including NPY, peptide YY (PYY), the NPY fragment 2-36 (NPY(2-36)), the Y(1) agonist [Leu(31), Pro(34)]-NPY and the Y(2) agonist NPY fragment 13-36 (NPY(13-36)), in two established anxiety models in rats: the elevated plus-maze and the fear-potentiated startle procedures. In the elevated plus-maze procedure, i.c.v. PYY (0.07-2.3nmol), NPY (0.07-2.3nmol), NPY(2-36) (0.07-2.3nmol). [Leu(31), Pro(34)]-NPY (0.7-7nmol), but not NPY(13-36) (0.7-7nmol), increased preference for the open arms of the plus-maze in a dose-dependent manner. In an acoustic startle paradigm, NPY, PYY and NPY(2-36) inhibited fear-potentiated startle over the dose-range of 0.23-2.3nmol. [Leu(31), Pro(34)]-NPY (2.3-13.2nmol) also attenuated fear-potentiated startle, whereas NPY(13-36) (up to 13.2nmol) had no effect. Taken together, these findings demonstrate that NPY, PYY and NPY(2-36) have anxiolytic-like effects that are likely mediated by Y(1) receptors.