Activity of choline acetyltransferase in the rat medial septal nucleus following fimbria-fornix transection or selective immunolesioning with 192 IgG-saporin

Changes in the biochemical activity of choline acetyltransterase in the medial septal nucleus, diagonal band and hippocampus were determined following bilateral fimbria-fornix transection or selective immunolesioning of cholinergic septohippocampal neurons with 192 IgG-saporin. Following axotomy, choline acetyltransferase activity in the medial septal nucleus not only persisted but increased much above control values 6 months postlesion, confirming that many cholinergic neurons survive the transection-of their axons. In contrast, immunolesioning led to a significant decrease in enzyme activity in the medial septal nucleus corresponding to the selective loss of septal cholinergic neurons in this lesion paradigm.