Spontaneous alternation of body turns and place: differential effects of amylobarbitone, scopolamine and septal lesions.

Sodium amylobarbitone, scopolamine and septal and hippocampal lesions all reduce spontaneous alternation. However, septal lesions appear to reduce alternation of places more than body turns, while the reverse is true for hippocampal lesions. The present experiments tested the effects of amylobarbitone and scopolamine on place and body turn alternation. Medial and lateral septal lesions were also tested. The former block hippocampal theta rhythm but the latter do not. Amylobarbitone (20 mg/kg, IP) reduced alternation of body turns to chance levels when this was present in control animals, but it did not affect alternation of place. Scopolamine (1.2 mg/kg, IP) reduced both body turn alternation and place alternation. Medial septal lesions produced significant perseveration of body turns and produced a non-significant reduction in place alternation. Lateral septal lesions, tested in a small number of animals, did not appear to affect alternation. The treatments thus reduce spontaneous alternation in differing ways which can in part be accounted for in terms of their differing effects on hippocampal theta rhythm.