Interleukin-2 regulates monoamine and opioid peptide release from the hypothalamus.

The present study determined whether interleukin-2 (IL-2) and IL-2 receptors are present in the adult rat hypothalamus. In addition, we determined whether IL-2 is involved in the regulation of neurotransmitter release from hypothalamic slices. In the hypothalamus, the highest levels of endogenous IL-2 and IL-2 receptors were localized to the median eminence and arcuate nucleus. Application of exogenous IL-2 to hypothalamic slices produced significant decreases of potassium (25 mM)-evoked [3H]noradrenaline release (24%) without significantly affecting the evoked release of [14C]glutamate, [14C]5-hydroxytryptamine, [3H]dopamine or [3H] gamma-amino butyric acid. In addition, IL-2 increased the potassium-evoked release of methionine-enkephalin (by 78%) and beta-endorphin (by 38%) from hypothalamic slices without affecting the release of leucine-enkephalin. In contrast, the spontaneous release of neurotransmitters and neuropeptides was not affected by exogenous IL-2. Overall, the findings of this study suggest that hypothalamic IL-2 is an endogenous neurokine that may be of consequence to the regulation of hypothalamic function.