The concentration of fibroblast growth factor (FGF), which is found in cerebrospinal fluid (CSF), markedly increases after the start of feeding. Food intake was dose-dependently suppressed by picomole doses of FGF and facilitated by anti-FGF antibody. This suppression was caused by activation of protein kinase C in glucose-sensitive neurons in the lateral hypothalamus. In situ hybridization by use of cDNA showed that acidic (a)FGF was produced in ependymal cells. The ependymal cells released aFGF by responding to glucose increase in CSF after feeding. Released aFGF diffused into the brain parenchyma and was taken by neurons. Passive avoidance was significantly more reliable after aFGF infusion into CSF. Clamping cerebral arteries in the gerbil induced ischemia, which damaged neurons in the CA1 layer of the hippocampus. Pretreatment with aFGF prevented this damage. Thus, aFGF is not only the most potent substance yet found for the suppression of feeding, but it is also extremely effective as a neurotrophic and memory facilitating substance.
Basic fibroblast growth factor (bFGF) has a neurotrophic effect on mesencephalic dopaminergic neurons in vitro and in vivo. To explore whether an abnormality in bFGF expression occurs in Parkinson's disease (PD), we examined the substantia nigra (SN) of six PD and eight control cases immunohistochemically using a monoclonal antibody to bFGF. The mean number of melanin-positive neurons in sections of PD SN was 30.3% of the control mean, but the number of bFGF-immunopositive neurons was only 4.7% of the control mean. bFGF-immunoreactivity was present in only 8.2% of PD, but in 93.7% of control melanin-positive neurons. These results suggest a profound depletion of bFGF in surviving dopaminergic neurons of the SN in PD, and this depletion may be related to the disease process.
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