Effect of tetanus toxin on basal and evoked release of 5-hydroxytryptamine and dopamine in rat hippocampus in vivo.

Tetanus toxin is a potent neurotoxin which produces seizures and usually death in mammals. In the present study, we have investigated the effect of tetanus toxin on extracellular basal and evoked release of 5-hydroxytryptamine (5-HT), dopamine (DA) and their metabolites in vivo, 7 days after toxin injection into the hippocampus of rats. Tetanus toxin decreased both basal and evoked release of 5-HT and DA. The 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) was not significantly decreased in the extracellular space. Of the DA metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) concentration was decreased while that of homovanillic acid (HVA) was unchanged. These findings are considered in light of the possible contributory role that a decrease in monoamine concentration in the hippocampus might have in the effects of tetanus toxin.