Characterization of neuropeptide Y, Y(2) receptor knockout mice in two animal models of learning and memory processing.

Neuropeptide Y (NPY) and, in particular, the Y2 receptor subtype, has been suggested to be involved in learning and memory processing. However, the precise role of Y2 receptors in learning and memory remains unclear. In the present study, mice lacking NPY Y2-type receptors were assessed in two animal models of learning and memory processing. We found that NPY Y2-/- mice displayed a deficit on the probe trial in the Morris water maze task, whereas acquisition performance, swim speed, and visible platform performance did not differ significantly between groups. In addition, NPY Y2-/- mice exhibited a marked deterioration in object memory 6 h, but not 1 h, following initial exposure in the object recognition test. Both groups of mice showed similar locomotor activity profiles in a low-stress, open field test. These data support the hypothesis that Y2 receptors are involved in the regulation of learning and memory processing.