NPY and NPY Y 1 receptor effects on noradrenaline overflow from the rat brain in vitro

Abstract

Neurotransmitters and neuropeptides play important roles in the regulation of various neuroendocrine functions particularly feeding. The aim of this study was to investigate whether a functional interaction occurs among neuropeptide Y (NPY) at NPY Y 1 receptors and noradrenaline overflow, as this may contribute to the regulation of appetite. The release of endogenous noradrenaline and its metabolite 3,4-dihydroxyphenylglycol (DHPG) were examined from hypothalamic and medullary prisms using the technique of in vitro superfusion and high performance liquid chromatography (HPLC) with coulometric detection. Noradrenaline and DHPG overflow was investigated at rest, in response to NPY (0.1 μM) and in response to the NPY Y 1 receptor agonist, [Leu 31,Pro 34]NPY (0.1 μM). Perfusion with NPY and [Leu 31,Pro 34]NPY significantly reduced noradrenaline overflow from the hypothalamus and medulla. Perfusion with NPY and [Leu 31,Pro 34]NPY was without significant effect on hypothalamic DHPG overflow, while medullary DHPG overflow was significantly reduced by NPY and [Leu 31,Pro 34]NPY. Results from this study provide evidence of NPY Y 1 receptor-mediated inhibition of noradrenaline release in the hypothalamus and medulla, further illustrating a complex interaction between neurotransmitters and neuropeptides within the rat brain.