Possible role of brain dopaminergic systems in the memory effects of central stimulants

In experiments on male Wistar rats trained and tested for memory retention on an active avoidance task in a maze, it was found that haloperidol at doses of 0.2 and 2 mg/kg injected intraperitoneally one hour prior to or immediately after training impaired learning and/or memory. The central stimulants caffeine (20 mg/kg), strychinine (1 mg/kg) and amphetamine (1 mg/kg) injected intraperitoneally immediately after training improved long-term retention; the central stimulants administered at the same doses but in combination with haloperidol (2 mg/kg) after training did not manifest their retention-facilitating effect. It is assumed that dopaminergic mechanisms underlie learning and memory processes in active avoidance conditioning and that an optimum activity of these mechanisms is necessary for the memory-facilitating effect of the central stimulants to appear.