MINAPRINE FACILITATES ACQUISITION AND RETRIEVAL OF AN ACTIVE-AVOIDANCE RESPONSE IN THE RAT

The nootropic activity of orpholino-ethylamino)-4-methyl-6-phenyl-pyri dazine dihydrochloride (minaprine) has been investigated in intact mal e, adult Long Evans rats by means of an active avoidance paradigm. In the light-dark box apparatus, the rat had to learn the active avoidanc e response of going out of the normally preferred dark chamber to avoi d electric foot-shocks. These were administered during one trial per d ay for 3 consecutive days (acquisition period). After a 72-h interval, rats underwent, for 3 consecutive days, one trial per day in which pu nishments were omitted (retrieval period). In the first experiment, ra ts were injected IP with minaprine (5, 10, and 25 mg/kg b.w.) 30 min b efore each trial of both periods. Rats injected with the two lower dos ages showed better responding during the retrieval period than control s (saline). On the contrary, the highest dosage impaired active avoida nce during both periods. In Experiment 2, minaprine (10 mg/kg b.w.) wa s administered either only during the acquisition or only during the r etrieval period. In both instances, active avoidance was equally enhan ced, if compared to controls (saline), only during the retrieval perio d. The results are discussed on the basis of the known facilitating ac tivity on cholinergic systems of this compound. It is concluded that m inaprine acts positively both on acquisition and retrieval of mnemonic traces.