The Neurobiological Effects of the Combined Impact of Anti-Orthostatic Hanging and Different Ionizing Irradiations

—The purpose of this investigation was to study the neurobiological effects of several interplanetary flight factors: hypogravity, which was modeled in a ground-based experiment using the conventional gravitational unloading technique, a 7-day anti-orthostatic hanging (AOH), and synchronous with it long-term gamma irradiation and high-energy protons. We analyzed the animal behavior in a number of tests: the open field, elevated plus maze, passive avoidance, Morris water test, and the exchange of monoamines in key brain structures. The most interesting and paradoxical result of our study is that in some cases effects were mitigated by the combined effect of radiation and microgravity, which manifests itself both in behavior and in neurochemical changes in all five studied brain structures, despite the fact that these structures play different roles in the performance of behavior. However, the isolated treatment with both radiation and AOH caused significant changes.