Effect of imidazole, papaverine and histamine on learning and memory in albino rats

In experiments for learning of albino rats in a maze and testing of the memory 24 hours and 30 days after learning, it was established that: Imidazole introduced i.p. in doses of 10, 30 and 60 mg/kg had no effect on learning, though it improved the memory both after administration 1 to 15 min before learning and when injected immediately after learning. Papaverine in doses of 2, 0.5 and 0.1 mg/rat and histamine in doses of 0.1, 0.01 and 0.001 mg/rat, introduced ventricularly before learning, make learning impossible (the large doses), deteriorate it (the medium doses), or have no effect on it (the small doses). Memory also deteriorates, with the exception of the smallest histamine dose. Introduced immediately after learning, the large dose of papaverine deteriorates memory, while the small dose results in a tendency to improve the memory indices upon testing 24 hours after the administration. The large dose of histamine administered after learning has no effect, the small dose results in a certain tendency to improve memory when tests are made 30 days after learning. The results obtained and their comparison with the results of previous works of ours involving other drugs with a known effect on the system of the cyclic adenosinemonophosphate (cAMP), e.g. haloperidol, lithium, caffeine and theophylline (in the doses tested), do not suggest any essential role of the effect of these drugs on the cAMP system in the mechanism of their effects on learning and memory.