Effects of Space Radiation and Combined Impact of Radiation and Other Spaceflight Factors on CNS Functions in Model Experiments on Animals Abstract—The effects of space radiation on the central nervous system, which are the most relevant to the assessment of radiation risk in interplanetary flights, can only be addressed in model ground-based experiments on animals. The article substantiates the methodology and presents the results of such experiments: long-term exposure to radiation was simulated using fractionated gamma irradiation of animals combined with exposure to hypogravity (antiorthostatic suspension of rats), and the specific effects of irradiation with 12C carbon ions and protons were simulated in accelerator experiments. Exposure to 12C ions has been shown to evoke significant changes in the brain monoamine metabolism, with the prefrontal cortex, the nucleus accumbens, and the hippocampus characterized as the most sensitive structures. However, the effects of exposure to high-energy protons in similar doses were almost similar to the effects of gamma radiation and could be characterized as minor.