The action of ciliary neurotrophic factor (CNTF) on intercellular free Ca2+ concentrations [Ca2+]1 induced by glutamate (Glu) in primary cultured hippocampal neurons were detected with Fura2/AM, a Ca2+-sensitive fluorophore. and the morphological influence of G-protein on it was ob-jected. Glu could induce rapid increase of [Ca2+]1 in hippo-campal neurons. CNTF had no significant action on [Ca2+]1 in resting hippocampal neurons. However, after incubation of CNTF for 5 min, the increase of [Ca2+]1 in hippocampal neurons rapidly induced by Glu was inhibited. Pretussis toxin (PTX)-sensitive G protein could block the action. These results indicate that a new non-genomic rapid sideway might exist in the upper stream of CNTF signal transduction pathway, which was related to Ca2+ signal transduction. The action of ciliary neurotrophic factor (CNTF) on intercellular free Ca 2+ concentration [Ca 2+] 1 induced by glutamate (Glu) in primary cultured hippocampal neurons were detected with Fura 2 / AM, a Ca 2+ -sensitive fluorophore. And the morphological influence of G-protein However, after incubation of CNTF for 5 min, the increase in [Ca 2+] 1 in hippo-campal neurons. CNTF had no significant action on [Ca 2+] 1 in resting hippocampal neurons. However, of [Ca2 +] 1 in hippocampal neurons rapidly induced by Glu was inhibited. Pretussis toxin (PTX) -sensitive G protein could block the action. These results indicate that a new non-genomic rapid sideway might exist in the upper stream of CNTF signal transduction pathway, which was related to Ca2 + signal transduction.