Gastrointestinal Peptide Binding and Function in the Brain: Emphasis on Peptide YY

Restraint stress potentiates neuropeptide Y-mediated impairment on spatial memory in rats

Memory is the ability to store, retrieve and use information that requires a progressive time-dependent stabilization process known as consolidation to be established. The hippocampus is essential for processing all the information that forms memory, especially spatial memory. Neuropeptide Y (NPY) affects memory, so in this study we investigated the participation and recruitment of NPY receptors during spatial memory consolidation in rats. Using the water maze test, we show that NPY (1 pmol) injected into the dorsal hippocampus impaired memory consolidation and that previous restraint stress (30 min) potentiates NPY effects, i.e. further impaired memory consolidation. Using selective antagonists for NPY Y₁ and Y₂ receptors we demonstrate that both receptors play a key role on spatial memory consolidation. Our data suggest that NPY modulates aversive and adaptive memory formation by NPY receptors activation.

Neuropeptide Y produces anxiety via Y2-type receptors

In the present study, the effects of intracerebroventricular (ICV) NPY, [Leu31, Pro34]NPY and NPY13-36 have been evaluated with respect to anxiety in mice in the elevated plus maze. NPY had opposing effects on behavior, depending on the doses used. NPY decreased the normal preference for the closed arms of the maze at 0.7 nmol, indicating an anxiolytic effect; however, at 7 pmol NPY further increased the preference for the closed arm, indicating an anxiogenic effect. [Leu31, Pro34]NPY, a Y1-type receptor agonist, significantly reduced the preference for the closed arms at 70 pmol. NPY13-36, a Y2-type receptor agonist, significantly intensified the preference at 20 pmol. It has been demonstrated that NPY produces not only an anxiolytic effect via Y1-type receptors, but also an anxiogenic effect via Y2-type receptors. The time course of these NPY actions are quite different and the anxiogenic effect was observed only shortly after ICV NPY injection.