Fasting affects more markedly neuropeptide Y than monoamines in the rat brain.

Monoamine turnover and neuropeptide Y (NPY) levels were evaluated in the CNS of 48- and 72-h-fasting adult, male rats in four brain areas: the hypothalamus, cortex, hippocampus, and striatum. In 48-h-fasted rats, NPY levels increased in the cortex and decreased in the striatum. The dopaminergic turnover increased in the hippocampus. The serotonergic turnover decreased in the hippocampus, striatum, and cortex and was still decreased after 72 h of fasting. In 72-h-fasted rats, an overall significant increase of NPY levels was observed except in the striatum, where it decreased significantly. No relationship appeared between NPY and monoamine levels, suggesting that NPY can act independently in feeding behavior and play, in different brain areas, an important role in its regulation.