CENTRALLY INJECTED NERVE GROWTH-FACTOR MODULATES PERIPHERAL IMMUNE-RESPONSES IN THE RAT

The effect of the intracerebroventricular (icv) and intravenous (iv) i njection of nerve growth factor (NGF) on peripheral immunity was studi ed in the rat. Icy administration of NGF (5, 25, 50, 250 and 500 ng/ra t) significantly enhanced phytohemagglutinin (PHA)-induced splenocyte proliferation 30 min after treatment. Icy pretreatment with an anti-NG F antibody completely prevented the effect, while iv injection of anti -NGF antibody did not block the effect of icy NGF. On the contrary, NG F at doses of 0.5, 2.5, 5, 25 and 50 ng/rat decreased splenocyte natur al killer (NK) activity. When injected iv, NGF enhanced splenocyte pro liferation only at doses of 50 and 500 ng/rat, while it did not affect NK activity. These effects on immunity do not appear mediated by acti vation of the hypothalamus-pituitary-adrenal axis, since NGF did not m odify plasma corticosterone concentrations at the doses used. These re sults indicate that NGF participates in the complex network of neuroim mune interactions.