The effect of a nanosecond pulse-periodic X-rays on the activity of the brain of mice

The effects of а nanosecond pulse-periodic X-ray on brain activity of mice were investigated. 108 white male mice weighing 25-30 g were irradiated by 4000 pulses of repetitive pulsed X-ray (maximum photon energy of 100 keV, pulse duration of 4 ns, pulse repetition frequency of 3-22 pps, and dose 0.2 and 1 Gy) daily for 10 days. The source of repetitive pulsed X-rays was the electron accelerator ''Sinus 150'', developed at the Institute of High Current Electronics SB RAS (Tomsk). Single exposure duration ranged from 3 to 20 minutes depending on the pulse repetition frequency. The behavioural components were assessed in the ''open field'' (horizontal and vertical components, hole-dipping activities, grooming and defecation) and recorded using a webcam. Then recorded files were examined and analysed, and all the behavioural responses were quantified. It was found that exposure of mice with the dose of 0.2 Gy at 16 and 22 pps increased the vertical activity by 20 and 30% respectively. Exposure with the same dose, but with frequencies of 13 and 22 pps increased the number of bowel movements by 60 and 25%. In addition, following the cranial irradiation of mice with a repetition rate of 13 pps and of 0.2 Gy the active searching and passive defensive behaviour components were activated. Exposure with the dose of 1 Gy was biologically effective for all pulse repetition. After exposure with low repetition rates (3 and 6 pps) the active searching component was activated by increasing the horizontal and vertical activity (5-10% and 20-30%, respectively). The effect is the opposite after exposure with a high repetition rate (8, 13, 16, 22 pps). In these conditions, the active searching component significantly inhibited in the form of reduced horizontal (30-40%) and hole-dipping activities (25-60%), but the passive-defence component was constant. It may indicate inhibition of excitation or activation of inhibition in the reticulo-cortical structures, but not the limbic ones. It is now known that a moderate dominance in the structure of the behaviour of the active searching component indicates the optimal behaviour on the whole, which is designed to meet the dominant need through interaction with the environment. In these experiments, the optimisation of mice behaviour in the ''open field'' was observed after exposure of the mice heads by repetitive pulsed X-ray with the dose of 0.2 Gy and repetition rate of 16 pps, and with the dose of 1 Gy at 3 and 6 pps. The rest of the repetition rates can be seen as maladaptive.

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