Combined effects of antiorthostatic suspension and ionizing radiation on the behaviour and neurotransmitters changes in different brain structures of rats

•The study of influence of microgravity (model antiorthostatic suspension) and the combined irradiation (gamma-rays and protons in Bragg peak) revealed significant apologies psycho-emotional status and cognitive abilities of experimental animals—rats.•Changes in the content of monoamines and their metabolites, and acetylcholine were detected in the hippocampus, hypothalamus and prefrontal cortex in response to the model of microgravity and ionizing radiation alone, but not in combination.•We retrieved the first evidences that microgravity model’s and ionizing radiation can act antagonistically regarding the psycho-emotional status and the cognitive abilities, which is also associated with a reduction of alterations in the monoamines content in the studied brain structures. Space flight factors (SFF) significantly affect the operating activity of astronauts during deep space missions. In contrast to an orbital flight, leaving the Earth’s magnetic field is fraught with the dangers of exposure to ionizing radiation and more specifically, the high-energy nuclei component of galactic cosmic rays. Microgravity, just another critical non-radiation factor, significantly affects the normal functioning of the CNS. Some morphological structures of the brain, such as the prefrontal cortex and the hippocampus, that are rich in monoaminergic and acetylcholinergic neurones, are the most sensitive to the effects of ionizing radiation and non-radiation spaceflight factors (SFF). In this work we have studied the combined effects of microgravity (in antiorthostatic suspension model, AS) and irradiation (γ-ray and protons in spread-out Bragg peak) on the behaviour, cognitive abilities, and metabolism of monoamines and acetylcholine in the key structures of the rat’s brain. Irradiation (as independently as combined with AS) resulted in the decrease of thigmotaxis in rats. Learning problems, caused by the malfunctioning of the working memory but not the spatial memory, were observed in response to AS as well as to the SFF in combination. Analysis of monoamines metabolism showed that the serotoninergic system was the most affected by the SFF. Concentration of acetylcholine in the hippocampus significantly increased in the groups of irradiated rats, and in the groups which were exposed to the SFF in combination, compared to the rats exposed only to AS.