Facilitative and Disruptive Effects of Strychnine Sulphate on Maze Learning

Abstract

Several studies (Rosenzweig, Krech, & Bennett 1956; Leukel, 1957; Pearlman, Sharpless, & Jarvik, 1959) have shown that, in rats, injections of depressant drugs administered either shortly before or shortly after training trials impair learning. These results, along with those obtained from studies of the retroactive effects of electroconvulsive shock and anoxia on learning (Thompson & Dean, 1955; Thompson & Pryer, 1956) support the general hypothesis that the amount learned on each trial depends upon the extent of perseveration of the neural activity initiated by the trial (Mueller & Pilzecker, 1900; Hebb, 1949). Since disruption of neural activity with central nervous system depressants has been shown to impair learning, it might be possible to facilitate learning by enhancing perseveration with central nervous system stimulants. To date there have been few investigations of this hypothesis. Strychnine sulphate is one of the most potent central nervous system stimulants. Physiological studies (Heinbecker & Bartley, 1939) have shown that in low concentrations strychnine lowers synaptic thresholds, while with high concentrations thresholds are raised. If it is assumed that degree of neural perseveration depends upon synaptic thresholds, then low doses of strychnine sulphate might facilitate learning. Lashley (1917) reported that low doses of strychnine sulphate facilitated the rate at which rats learned a Watson maze. Recently, McGaugh and Petrinovich (1959) reported similar findings using a Lashley 111 alley maze. A further study of this problem using a complex 14-unit alley maze is reported here.