Ornithine decarboxylase induction and polyamine synthesis in the kindling of seizures: the effect of alpha-difluoromethylornithine.

It has been suggested that the kindling of seizures may depend on the induction of genes encoding enzymes involved in neurotransmission. Experimental seizures are followed by an especially rapid and massive induction of brain ornithine decarboxylase (ODC), an enzyme which catalyses the rate-limiting step in the synthesis of polyamines. The latter compounds have been shown to act as positive allosteric modulators of the NMDA receptor, and also to play an important role in cell growth and differentiation. The induction of ODC by seizures has accordingly been suggested to play a pivotal role in the changes in synaptic structure and function that underlie kindling. In the present study we examined the progress of kindling during treatment with alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC. We found that progressive increase in the duration and severity of kindled seizures and in the duration of local afterdischarges was unaffected by daily injections of DFMO in doses previously shown to cause substantial depression of brain ODC activity. Treatment with DFMO also failed to produce significant anticonvulsant or proconvulsant effects. Progressive increase in seizure activity during kindling is therefore unlikely to depend to any appreciable extent on enhanced synthesis of polyamines by ODC.