[Participation of dihydropyridine-sensitive calcium channels in psychotropic effects of nootropic drugs]. / Uchastie digidropiridinchuvstvitel'nykh Ca-kanalov v psikhotropnom éffekte nootropnykh preparatov.

Administration of Ca-entry blockers with different chemical structure before the braining sessions produced the reduction of memory retention in mice and rats in the one-trial passive avoidance tests. This effect was absent in animals treated immediately after training test. Nootropic drugs piracetam and oxiracetam corrected the retention of memory when injected just after training test. Chronic treatment of rats with increasing doses of the nootropic drugs produced about two-fold tissue-specific elevation in the density of DHP-receptors, associated with L-type Ca-channels in synaptosomal membranes of rat cerebral cortex. Maximal effect was observed in a dose of 10 mg/kg. Diltiazem, administrated in a dose of 10 mg/kg, produced about two-fold decrease in the receptors density measured 24 hrs after the first injection. Oxiracetam (10 mg/kg) completely antagonized the effect of Ca-entry blocker. These data imply that nootropic action of piracetam and oxiracetam is mediated by L-type Ca-channels.

Calcium entry blockers and oxiracetam have opposite effects on the density of dihydropyridine receptors in rat cerebral cortex.

Ca2+ entry blockers riodipine, D-cis-diltiazem and verapamil, when administered i.p. to rats at a dose of 10 mg/kg, produced two-fold decreases in the density of 1,4-dihydropyridine (DHP) receptors in rat cerebral cortex, as revealed by Scatchard plot analysis of radioligand binding made 24 h after the first injection. Thereafter, the number of DHP binding sites increased up to the initial level on day 4 of the treatment. The nootropic drug oxiracetam, when injected simultaneously with Ca2+ channel blockers at a dose of 10 mg/kg, prevented this transient decrease in DHP receptor density in brain. These results can explain the opposite modulation of memory retention by calcium antagonists and nootropic drugs that has been observed previously.

[Comparative influence of nootropic preparations on the emetic effect of morphine]. / Sravnitel'noe vliianie nootropnykh preparatov na émeticheskii éffekt morfina.

The effect of electroshock (ECS) and piracetam, oxiracetam or N-acetylglycinamide on the passive avoidance conditioned response in rats was studied. The antiemetic effect of the compounds was examined in cats as well. The results obtained allowed us to distinct the nootropic and antiemetic action of the drugs. The substances possessed a similar ability to prevent ECS-induced amnesia. On the contrary, oxiracetam completely prevented the emetic response to morphine at doses 100 times lower and piracetam at doses 10 times higher then those of the opioid. N-Acetylglycinamide had no antiemetic activity. The results obtained show that oxiracetam is 100 times more active in antiemetic test than piracetam. These data comprise the novel properties of nootropic drugs.