An investigation of the single and combined effects of hypogravity and ionizing radiation on brain monoamine metabolism and rats' behavior.

Background: Ionizing radiation and hypogravity can cause central nervous system (CNS) dysfunctions. This is a key limiting factor for deep space missions. Up until now, the mechanisms through which they affect the neural tissue are not completely understood.

Objectives: We studied how the combination of hypogravity (antiorthostatic suspension model, AS) and ionizing radiations (γ-quanta and H together, R) affects the CNS.

Methods: We applied separately and in combination AS and R to determine the influence of these factors on behavior and metabolism of monoamines in Wistar rat's brain.

Results: We found out that R has a slight effect on both the behavior and metabolism of monoamines. However, when applied in combination with AS the former was able to reduce the negative effects of the latter. The combined effect of ionizing radiation and hypogravity led to the recovery of locomotor activity, orientation and exploratory behavior, and long-term context memory impaired under the impact of hypogravity only. These changes came together with an increase in the serotonin and dopamine turnover in all of the brain structures that were studied.

Conclusions: We received the first evidence of interferential interaction between the effects of ionizing radiation and hypogravity factors with regard to a behavior and monoamine turnover in the brain. Further studies with heavy nuclei at relevant doses (<0.5 Gy) are needed.