Neuropeptide Y receptor subtypes in the basolateral nucleus of the amygdala modulate anxiogenic responses in rats

The behavioral effects induced by intra-amygdala stimulation of the neuropeptide Y (NPY) Y 2 and the NPY Y 5 receptor subtypes were assessed in the social interaction (SI) test. Microinjections of NPY 3–36, an NPY Y 2 preferring agonist, into the basolateral nucleus of the amygdala (BLA) produced bi-directional dose–response curve. At low doses NPY 3–36 has an anxiogenic effect while at higher doses it produced an anxiolytic effect. Pretreatment with the NPY Y 5 receptor antagonist Novartis 1(1 nmol), an analog of CGP71683A synthesized by Eli Lilly and Company, IN, blocked the anxiolytic effects of NPY 3–36 (80 pmol), while pretreatment with BIBO 3304 (200 pmol), a Y 1 antagonist, had no effect, suggesting that the Y 5, but not the Y 1 receptor was involved in the anxiolytic behavior produced following intra-amygdalar NPY 3–36 administration. In addition, the Y 5 antagonist had no behavioral effect when given alone at 1.0 nmol. These findings support the hypothesis that amygdalar Y 2 receptors may play a role in mediating anxiogenic effects, while Y 5 receptors may be involved in the anxiolytic behaviors of NPY.