Hippocampal damage produced by tetanus toxin in rats can be prevented by lesioning CA1 pyramidal cell excitatory afferents.

The neuropathological effects induced by tetanus toxin (TT) bilaterally microinjected into the hippocampus were studied in rats bearing a surgical unilateral lesion of the Schaffer collaterals. TT (1000 mouse minimum lethal doses, MLDs; n = 5 rats) produced neurodegeneration in the CA1 pyramidal cell layer in the unlesioned side of the hippocampus ten days after injection. By contrast, the injection of TT into the lesioned hippocampus produced no degeneration. In rats bilaterally treated with BSA (n = 3 rats) no neuropathological effects were observed in either hippocampi. In conclusion, our results have demonstrated that the lesion of the Schaffer collaterals may protect against the neuropathological effects induced by TT in rats.