COMPUTER-ASSISTED MAPPING OF BASIC FIBROBLAST GROWTH-FACTOR IMMUNOREACTIVE NERVE-CELL POPULATIONS IN THE RAT-BRAIN

We have performed a mapping of basic fibroblast growth factor (bFGF) i mmunoreactive (ir) glial and nerve cell populations in the male rat br ain using a rabbit antibody raised against a synthetic peptide of bovi ne bFGF. Regional morphometric and microdensitometric analysis of the bFGF ir neuronal profiles in coronal brain sections was carried out by means of an automatic image analyser. The density and intensity of th e bFGF ir glial profiles were subjectively evaluated. The bFGF immunor eactivity (IR) was detected within the cytoplasm of neurons, except wi thin the pyramidal neurons of hippocampal CA2 region, the fasciola cin erea and the indusium griseum, where bFGF IR was present in the nucleu s. In contrast, in glial cells bFGF IR was always found in the nucleus , Neuronal and glial IR was no longer observed after absorption of the bFGF antiserum with recombinant bFGF. Basic FGF IR was found in neuro nal and glial cell populations throughout the brain as well as in the choroid plexus and in the ependymal cells lining the ventricles, Basic FGF ir nerve cells were found in all layers of both the neocortex and allocortex. Within the caudate putamen and the nucleus accumbens a lo w density of weak bFGF ir neuronal profiles was detected, The majority of the thalamic nuclei showed medium to high densities of moderate to strong bFGF ir neuronal profiles. All the hypothalamic nuclei, with t he exception of the anterior and lateral hypothalamic area and of the ventral hypothalamic nucleus, contained a high density of bFGF ir prof iles, The pens and the medulla oblongata were characterized by the pre sence of a large number of nuclei containing moderate to high densitie s of strong bFGF ir profiles. The Purkinje cell layer of the cerebella r cortex contained a high density of moderately bFGF ir profiles. A mo derate density of strong bFGF ir nerve cell profiles was observed with in all the laminae of the spinal cord, except within the II and III la minae where a high density of strongly ir profiles was found. Histogra m analysis of total immunoreactivity showed that the distribution of b FGF ir profiles within the telencephalon and mesencephalon tend to be similar with regard to the central tendency and spread. Using Kendall' s tau, a significant correlation between intensity and density values was obtained only in the diencephalon. The cytoplasmic bFGF IR found i n distinct nerve cell populations all over the rat brain and spinal co rd may represent forms of bFGF which can be released from the nerve ce lls via non-exocytotic mechanisms in view of the absence of an intrace llular signal peptide in bFGF. The presence of nuclear bFGF IR within the glial cells all over the central nervous system (CNS) suggests an intracellular function of bFGF, such as the promotion of mitogenesis a nd/or participation in the transcriptional regulation of various genes .