Effects of intra-amygdaloid injections of alpha-difluoromethylornithine and putrescine on the development of electrical kindling in rats.

In our previous study, an increase in concentration of putrescine was observed in the brain of amygdaloid kindled rats. To clarify the role of putrescine in kindling, the effects of intra-amygdaloid injections of alpha-difluoromethylornithine (DFMO), an inhibitor of polyamine synthesis, or putrescine on the development of electrical kindling were examined in rats. Kindling stimulations were applied to the left amygdala. Pretreatment with DFMO (50 nmol) for 10 days by injection into the ipsilateral amygdala decreased both the number of stimulations and total afterdischarge (AD) duration required to reach first fully kindled state. Kindling-induced elevation of the putrescine concentration was inhibited by pretreatment with this dose of DFMO. On the other hand, pretreatment with putrescine (200 nmol) for 10 days into the same site of the brain retarded the behavioral and electrographic development of kindling seizure during the period of drug administration, although these treatments did not produce any changes in the number of stimulations or total AD duration. Putrescine (200 nmol) demonstrated no anticonvulsive effects in previously kindled animals. These results suggest that putrescine has an inhibitory effect on the development of amygdaloid kindling in rats.