Journal: The Journal of Neuroscience
Article Title: Circulating Insulin-Like Growth Factor I Mediates Effects of Exercise on the Brain
Figure Lengend Snippet: Physical exercise and intracarotid injection of IGF-I produce similar effects in the brain. A , The same brain areas show labeling of neurons with IGF-I after treadmill running ( a–c ) and intracarotid injection of IGF-I ( d–f ). Three representative areas are shown. Nonexercised, saline-injected rats show almost undetectable brain IGF-I staining ( B ). Str , Striatum; Cx , cerebral cortex; RN , red nucleus. Biotinylated anti-rabbit IgG followed by Cy3-streptavidin was used after incubation with a polyclonal anti-IGF-I antibody. B , Digoxigenin ( DIG ) and IGF-I colocalize within the same neurons after intracarotid injection of DIG–IGF-I. A representative field in the brainstem is shown. a , Low magnification (10×) of IGF-I staining in the inferior olive nucleus ( IO ) of a saline-injected rat. Note the absence of signal. Inset , Higher magnification (40×) of the IO field. b , The same field showing IGF-I staining in an IGF-I-injected rat. Inset , High magnification showing IGF-I-positive cells. c , High magnification (40×) of IO neurons stained with a monoclonal anti-DIG antibody ( green ). d , The same field stained with a polyclonal anti-IGF-I antibody ( red ). e , Colocalization of DIG and IGF-I within the same IO neurons. Scale bars: a , b , 500 μm; c – e , 50 μm. Primary antibody incubation was followed by an anti-rabbit Cy2 and anti-mouse Cy5, respectively. C , Exercise or intracarotid injection of IGF-I elicits a similar pattern of increased c-Fos staining throughout the brain. Only the piriform cortex ( Pir ) is shown as a representative area. a , Control animals show no c-Fos staining. b , c-Fos staining after 1 hr of intracarotid injection of IGF-I. c , c-Fos staining after 1 hr of running. Scale bar ( a – c ): 500 μm. d , Higher magnification of the field in c showing nuclear localization of the c-Fos signal. Scale bar, 50 μm. Arrows indicate immunoreactive cells. A monoclonal anti-c-Fos antibody followed by a biotinylated anti-mouse IgG and Cy3-streptavidin was used. D , Blockade of the exercise-induced capture of IGF-I by brain cells results in absence of c-Fos labeling after exercise. a , IGF-I labeling in the hippocampus of a rat that ran for 1 hr. c , Chronic intracerebroventricular delivery of a combination of an anti-IGF-I antibody and an IGF-I receptor antagonist results in absence of IGF-I staining after 1 hr of running exercise. Scale bar ( a , c ): 50 μm. b , c-Fos staining is induced in the hippocampus by 1 hr of running. c , No c-Fos labeling is seen in exercised animals in which brain uptake of IGF-I is blocked. Scale bar ( b , d ): 500 μm. The hippocampus is shown as a representative area, but absence of labeling for IGF-I and c-Fos was found in all brain areas. E , Expression of BDNF in the hippocampus is increased by running and by intracarotid injection of IGF-I. Control: background BDNF RNA staining in brain slices incubated with excess unlabeled probe. Saline: animals injected with saline show weak BDNF expression in the hippocampus. Exercise: running induces increased expression of BDNF in the hippocampus. IGF-I: injection of IGF-I produces a similar increase in hippocampal expression of BDNF. Cx , Cortex; Hy , hippocampus.
Article Snippet: The secondary antibodies that were used were biotinylated goat anti-mouse IgG (1:1000) (Jackson ImmunoResearch, West Grove, PA) or anti-rabbit IgG (1:250–1:1000) (Pierce, Rockford, IL).
Techniques: Injection, Labeling, Staining, Incubation, Expressing