Aberrant Timm‐stained fibres in the dentate gyrus following tetanus toxin‐induced seizures in the rate

The present study addresses whether seizures, which result from the chronic block of inhibition caused by an intrahippocampal injection of tetanus toxin, induce axonal sprouting of the hippocampal mossy fibres. Timmstain was used to identify the mossy fibre terminals. in nin of 15 animals killed at 1 month or later after an injection of tetanus toxin. Timm‐stained terminals were observed bilaterally in the inner molecular layer and in seven animals a meshwork of Tim‐stained fibres/terminals was also abserved bilaterally in the outer molecular layer of the fascia dentata. None of these changes were observed in any of the 12 saline‐injected controls. There was no obvious correlation between the number of motor fits an animal exhibited and the amount of Timma‐stained fibre sprouting present in either the inner or outer molecular layer. The Timm‐satined exonal sprouting into the outer molecular layer of the fascia dentata may simply reflect the reinnervation of sites on the granule cell dendrites. previously occupied by the terminals of the hilar somatostatin‐containing cells. These hilar somatostatin‐containing cells which are believed to project to the outer molecular layer are known to succumb to the seizure activity in this animal model of epilepsy.