Conditioned fear-induced changes in neuropeptide Y-like immunoreactivity in rats: the effect of diazepam and buspirone

The study aimed to investigate the influence of conditioned fear, produced in the passive avoidance test, on neuropeptide Y-like immunoreactivity (NPY -LI) and the effect of anxiolytics on NPY-LI in frightened rats. Rats avoid ed the dark chamber, where they were previously subjected to electric foots hock, and they exhibited increased numbers of defecations and gastric ulcer s. Moreover, they showed increased NPY-LI in the amygdala, nucleus accumben s and hypothalamus, and decreased NPY-LI in the frontal cortex. Diazepam (1 or 3 mg/kg) and buspirone (1.5 or 5 mg/kg) dose-dependently inhibited pass ive avoidance and decreased the numbers of defecations, and they also decre ased the number of gastric ulcers. Diazepam reversed while buspirone only a ttenuated the fear-induced changes in NPY-LI in ail regions studied. In the amygdala, the effect of diazepam was dose-dependent. The effect of diazepa m on both behaviour and NPY-LI was antagonized by flumazenil (15 mg/kg). Ap art from supporting the role of the NPY system in fear and anxiety, the res ults of this study suggest that NPY is involved in the anxiolytic effects o f diazepam and buspirone and that the effect of diazepam is mediated by ben zodiazepine receptors. (C) 2000 Harcourt Publishers Ltd.