Action of interleukin-2 and interleukin-4 on CRF mRNA in the hypothalamus and POMC mRNA in the anterior pituitary.

We have used the technique of in situ hybridization histochemistry to determine corticotropin-releasing factor (CRF) mRNA in the hypothalamic paraventricular nucleus (PVN) and proopiomelanocortin (POMC) mRNA in the anterior pituitary of rats given a single ip injection of either interleukin (IL)-2 or IL-4. IL-2 increased POMC mRNA in the anterior pituitary in a dose-dependent manner. The effect was apparent both at 4 and 24 h after injection. No effect of IL-2 on CRF mRNA in the PVN was detected in these animals, suggesting that the increase in POMC mRNA was not driven by an increase in CRF. IL-4 was without effect at the hypothalamic level although this cytokine did result in a decrease in POMC mRNA in the anterior pituitary.