[Effect of the psychostimulants caffeine and methylphenidate on the efficiency of physical activity in rats exposed to ionizing radiation].

The authors carried out studies on 267 male rats and examined the effect of ionizing irradation (single irradation with 737 roentgens) on the duration of swimming and on the alteration of this effect by psychic stimulators caffeine and methylphenidate, administered in overthreshold doses (30 and 50 mg/kg of body weight for caffeine and 5 and 10 mg/kg of body weight for methylphenidate). On the 7th day after irradiation there was statistically significant shortening of the duration of swimming in the control animals. The mentioned doses (statistically significant for the larger dose) were used in nonirradiated animals and the two psychic stimulators also shortened the duration of swimming in comparison with the control nonirradiated animals. This effect could be explained by hyperexcitatory action of these doses of caffeine and methylphenidate. As a result of this, desoptimization of the cerebral activity occurred and as a consequence of which was the diminution of the efficiency of the physical activity. Together with this they observed that both psychic stimulators partially counteracted the shortening of the duration of swimming of rats, caused by ionizing irradiation itself. This effect, especially for caffeine, could be explained by the induced of the ionizing irradiation increase in the sensitivity of cerebral phosphodiesterase of rats to its inhibitor caffeine as a result of which under these conditions the effect of caffeine on the level of cerebral cyclic AMP was reinforced. The cyclic AMP is presumed to have some protective effect against ionizing irradiation.