Aortic coarctation hypertension induces fibroblast growth factor-2 immunoreactivity in the stimulated nucleus tractus solitarii.

The actions of neurotrophic factors i.e. basic fibroblast growth factor (bFGF, FGF-2) to neurons are related not only to neuronal development and maintenance but also to synaptic plasticity regarding neurotransmission. We analyzed here the levels of FGF-2 immunoreactivity in the nucleus tractus solitarii (NTS) of Wistar Kyoto rats in response to alterations of neuronal activity promoted by the stimulation of the baroreceptor reflex following an aortic coarctation-induced-hypertension. The FGF-2 immunoreactivity (IR) was found in the cytoplasm of the neurons and in the nuclei of the glial cells in the NTS. A large number of NTS neurons expressed FOS immunoreactivity 4 h after coarctation, as an indication of neuronal activity. Stereological methods showed an increased number of FGF-2 immunoreactive (ir) neuronal profiles (90%) and glial profiles (149%) in the NTS of the 72 h aortic coarctated rats. 1-week later, FGF-2 ir neurons were still increased (54%) but no change was found in the number of FGF-2 ir glial profiles. The double immunoperoxidase method revealed that the majority of the FGF-2 ir glial cells was glial fibrillary acidic protein (GFAP) positive astrocytes. GFAP immunohistochemistry showed an astroglial reaction at 72 h time-interval (55%) but not 1 week after stimulation. The number of the cresyl violet positive neurons and OX42 ir profiles (marker of activated microglia) in the NTS of coarctated rats were not different from control by 1 week and 1 month after the surgery, indicating a lack of NTS injury in this period following coarctation hypertension. FGF-2 may be an important neurotrophic factor in areas involved in the control of blood pressure. The increased FGF-2 IR in the NTS cells following neuronal stimulation may represent trophic and plastic adaptive responses in this nucleus in an autocrine/paracrine fashion.