Interaction between cholinergic and catecholaminergic agents in a spontaneous alternation task.

Spontaneous alternation was examined in a free running Y-maze task after various pharmacological manipulations. Whereas scopolamine reduced alternation to chance levels, d-amphetamine in some doses resulted in alternation significantly below chance (perservation). Physostigmine treatment increased levels of alternation whereas reserpine was without effect. Concurrent administration of drugs revealed that reserpine effectively reversed the effects of scopolamine, while the perseveration induced by d-amphetamine was antagonized by physostigmine. When animals were pre-exposed to the Y-maze the effects of d-amphetamine were enhanced, but effects of scopolamine were not modified. Finally, scopolamine treatment augmented the perseverative effects of d-amphetamine. It was suggested that cholinergic agents modify alternation by effects on habituation. On the other hand d-amphetamine produces genuine perseveration without effects on habituation per se. Alternation performance and perseveration were suggested to be mediated by the interaction between the distinct behavioral effects of cholinergic and catecholaminergic activity.