An Interdisciplinary Study of the Effects of 6-OHDA Lesions of the Septum on Cholinergic Septo-Hippocampal Activity in Inbred Mouse Strains

The functional activity of the cholinergic neurones of the septohippocampal pathway has been postulated to play an important role in learning and memory processes (Jaffard and Destrade, 1982) and is transsynaptically regulated by numerous neurotransmitter systems, including dopamine, in the septum (Costa et al., 1983). A10 dopamine terminals mediate a tonic inhibitory control on these cholinergic neurones and Durkin et al. (1983) reported that significant genotypic variation exists for this dopaminergic control in the C57BL/6 and BALB/c mouse strains and that this variation may underly strain differences in learning and memory performance. We therefore decided to undertake an interdisciplinary study of the effects of 6-OHDA lesions of the lateral septum (3µg/1 µl, bilateral) in C57BL/6 and BALB/c mice. Between 6 and 12 days post-operation their alternation behaviour, acquisition, retention and reversal of a spatial learning task was tested in a T-maze and compared to vehicle-injected and intact controls. 6-OHDA injected mice exhibited higher rates of spontaneous alternation and a facilitation of both acquisition and reversal of the spatial discrimination, these facultative effects being significantly greater in C57BL/6 mice as compared to BALB/c.