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The experiments were carried out on 104 male white rats and the effects of pyracetamat, aniracetamat and 2 newly synthesized pirolidine derivatives P-CL, P-p as well as of cytidin-diphosphat choline (cyticholine) were examined on training in a water maze. All investigated substances were administered immediately after morning training orally in a dose of 100 mg/kg for a period of 5 days. Ten trainings were undertaken each day twice. Two parameters were determined: time of stay of the rat in the water maze (in seconds) and the number of mistakes (entrance of blind canals). Pyracetamat and cyticholine improved training of rats while the other examined substances showed insignificant effect. A conclusion is made that chemically close nootropic drugs could be differentiated substantially in respect to spatial memory as well.

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.

The authors administered 50 mg/body weight of centrophenoxine in white rats i.p. for five susseccive days. The content of serotonine in the cerebral cortex, brain stem and cerebellum increased statistically significant in the rats, injected with centrophenoxine. The levels of noradrenaline and dopamine in the brain stem were raised also significantly. Centrophenoxine did not alter the content of cyclic AMP and the activity of phosphodiesterase in the cerebral cortex and brain stem. These data gave foundation to the authors to suggest that in the mechanism of action of centrophenoxine a significant role is given to the changes, induced by this preparation in the content of biogenic amines in the brain stem.

The authors carried out studies on isolated segmets of ileum with a length of 3 sm. obtained from both male and female, mature and immature guinea pigs and adult male and female rats as well as on isolated vasa deferntia, obtained from guinea pigs and rats. They examined the influence of a group of substances, known as stimulators and inhibitors of adenyl-cyclase and phosphodiesterase (isoprenaline, lithium sulfate, imidazol, theophiline and eupaverine) on the spasmogenic effects of acethylcholine (on ileum) and of noradrenaline (on vas deferens). These substances were used in doses, which were subthreshold in respect to their effect on the biogenesis and exzymic inactivation of the cyclic AMP. The authors found certain species, adult and sex differences in the spasmogenic effects of acethylcholine and noradrenaline. The examined substances lowered the spasmogenic effects of acethylcholine and noradrenaline in most of the experiments. Since the examined substance-classical means for altering the endogenous production of the cyclic AMP-show antispasmogenic effect in concentrations subthreshold for their influence on the level of the cyclic AMP, an inference is made that their inherent antispasmogenic effect is due also to a mechanism, which does not require the inclusion of the system of the cyclic AMP.

The authors carried out experiments on isolated vasa deferentia, obtained from a guinea pig. Recordings of the isotonic contractile activity was made by means of a strain gauge. Ink records were made on graduated tape of miliampermeter Tesla. Acethylcholine was used in a concentration of 1 X 10(-5) M, but serotonine-in a concentration of 1 X 10(-5) M. Growing reduction of the values was observed very regularly in all experiments both in the serotonine and acethylcholine contractions of vas deferens after diminution of the content of calcium in the Krebs solution from 0,9 to 0,15 mM. Gradual recovery of the value of the spastic effects of the examined substances was observed after placing the isolated organ in Krebs solution with a normal content of calcium. In analogous role of calcium in the spastic effects of the two mediators there were also some differences in the dynamics on which this role was manifested. The authors discussed the significance of the external calcium for the realization of the contractile effects of acethylcholine and serotonine on vas deferens of a guinea pig.

The authors examined the influence of x-ray irradiation on phosphodiesterase system in the brain of rats and the sensitivity of the enzyme to inhibitors (caffeine, theophyline, thyopental) and activators (imidozol). The animals (Wistar with weights of 150--200 gm/were irradiated singly with a dose of 737 r. Phosphodiesterase activity (PD) was determined by the method of Filburn and Carn (1972) at two substrate concentrations (1 and 100 microM). X-ray irradiation did not change PD with high Km, while the enzyme with low Km was reduced significantly and transitionaly. Caffeine, theophyline and thyopental inhibited more PD with low Km in the irradiated rats in comparison with the control nonirradiated rats. The activating effect of imidazol on PD with low Km was more marked in irradiated rats. These data could be interpreted in the light of the molecular mechanisms, determining the altered action of some drugs after x-ray irradiation.