Diazepam and buspirone alter neuropeptide Y-like immunoreactivity in rat brain

Neuropeptide Y-like immunoreactivity (NPY-LI) was investigated in naive Spr ague-Dawley rats subjected to acute, subchronic (7 days) or chronic (21 day s) intraperitoneal treatment with diazepam (1 or 3 mg/kg once daily) or bus pirone (1.5 or 5 mg/kg twice daily). NPY-LI was determined by radioimmunoas say in the amygdala, nucleus accumbens, hypothalamus and frontal cortex 24 h after the last dose of the drugs. Amygdala NPY-LI decreased after acute d iazepam (3 mg/kg) or buspirone (1.5 mg/kg) and increased after subchronic t reatment with both doses of diazepam and after chronic buspirone (1.5 mg/kg ) treatment. Both diazepam and buspirone given in subchronic and chronic do ses decreased NPY-LI levels in the nucleus accumbens. Hypothalamic NPY-LI c hanged only after chronic treatment: it decreased after diazepam and increa sed after buspirone (5 mg/kg). NPY-LI content in the frontal cortex decreas ed after subchronic diazepam (3 mg/kg) treatment and slightly increased aft er buspirone. The study has shown that both diazepam and buspirone affect N PY-LI levels in rats. These results suggest that the NPY system in the amyg dala and nucleus accumbens is implicated in the anxiolytic effects of the d rugs studied. (C) 1999 Harcourt Publishers Ltd.