Reversible septal inactivation disrupts hippocampal slow-wave and unit activity and impairs trace conditioning in...

This study investigated the effects of medial septal microinfusion of the local anesthetic, procaine (MS Pro), on hippocampal neurophysiology and learning of the rabbit (Oryctolagus cuniculus) classically conditioned jaw movement (CJM) response. Both the percentage and the amplitude of hippocampal theta decreased after procaine administration, and unit recordings from the MS Pro group showed significantly smaller conditioning-related hippocampal neural responses than those from controls. The MS Pro group took significantly longer to reach learning criterion than did the control group. Interpreted in the context of previous studies, the present result suggests that nonselective blocking of all septal projection systems, as well as fibers of passage, using procaine can be less detrimental to learning than an imbalance between GABAergic and cholinergic septohippocampal projections, as produced by septal infusion of anticholinergics.