Double immunofluorescence and laser confocal microscopy showing co-localization (yellow) of the dopaminergic marker TH (green; A.-D., the astroglial marker GFAP (green), E., F. or the microglial marker OX-42 (green), G.-J., and IGF-1 (red), A., C., E., G., I. or IGF-1R (red), B., D., F., H., J. Dopaminergic neurons in primary cultures and MES 23.5 dopaminergic neurons showed immunopositivity for IGF-1 A., C. and IGF-1R B., D.. Immunolabelling for IGF-1 and IGF-1R was also detected in primary astrocytes E., F. and more intense immunolabeling for both IGF-1 and IGF-1R was observed in primary microglia G., H. and the N9 microglial cell line I., J.. The relative intracellular levels of IGF-1 and IGF-1R was estimated by computer-assisted fluorescence intensity measurements K., L.. Data represent means ± SEM. *p < 0.05 compared with control group (N9 microglial cells); #p < 0.05 relative to primary microglia; $p < 0.05 relative to primary dopaminergic (DA) neurons; &p < 0.05 relative to MES 23.5 DA neurons. One-way ANOVA and Holm Sidak post-hoc test. Scale bars: 10 μm. GFAP, glial fibrillary acid protein; IGF-1-R, IGF-1 receptor; TH, tyrosine hydroxylase; primary NG, primary neuron-glia mesencephalic cultures.