ANIRACETAM IMPROVES BEHAVIORAL-RESPONSES AND FACILITATES SIGNAL-TRANSDUCTION IN THE RAT-BRAIN

The effect of aniracetam (10, 50, 100 mg/kg i.p. daily for 15 days) on both behavioural and biochemical parameters was investigated in the a dult rat. Animals given aniracetam (50 mg/kg 1 h before the trial) sho wed a significant increase in the percentage of conditioned active avo idance responses and a reduction of latency times. Aniracetam signific antly counteracted the scopolamine-induced memory failure at the passi ve avoidance (step down) test, while it did not modify the locomotion of the animals. In purified frontocortical and hippocampal synaptic me mbranes of rats treated with aniracetam (50 mg/kg i.p. daily for 15 da ys) a potentiation of basal, carbamylcholine-, dopamine- and norepinep hrine-stimulated adenylyl cyclase activity was observed, while forskol in-stimulated enzyme activity was not modified. With regard to inosito l phosphate production measured in fronto-cortical synaptoneurosomes, aniracetam potentiated the stimulation by angiotensin II, while the st imulation by carbamylcholine, not affected by 10 and 50 mg/kg aniracet am, was notably, although not significantly, decreased by 100 mg/kg an iracetam. Furthermore, in synaptosomes derived from hippocampus, anira cetam (50 mg/kg i.p. daily for 15 days) caused an increase of both bas al and K+-stimulated intrasynaptosomal. Ca2+ concentration. In conclus ion, a correlation between the improvement of behavioural performance and the modulation of transducing systems by aniracetam seems to take place in brain areas, such as frontal cortex and hippocampus, known to play a major role in the control of cognitive functions.