Involvement of putrescine in the development of kindled seizure in rats.

During the development of kindling by daily electrical stimulations applied to the left amygdala of rats, concentrations of the polyamines putrescine, spermidine, and spermine were measured in the left amygdala and the remainder of the cerebrum. A significant increase of putrescine concentration appeared first at the left amygdala in prekindled rats and then propagated to the remainder of the cerebrum with the development of kindling. This increase in putrescine concentration in the left amygdala was higher in prekindled rats than in fully kindled rats and lasted for at least 24 h after the final kindling stimulation. The concentrations of spermidine and spermine were slightly increased in a fully kindled state. To clarify the role of putrescine in kindling, the development of amygdaloid kindling was examined in rats after microinjections of alpha-difluoromethylornithine, a specific inhibitor of polyamine synthesis, and putrescine into the ipsilateral amygdala. Pretreatment with alpha-difluoromethylornithine (50 nmol) for 10 days accelerated both the development of behavioral kindling and the propagation of the afterdischarge from the left amygdala to the frontal cortex. In contrast, pretreatment with putrescine (200 nmol) for 10 days retarded the development of kindling. These results suggest that the increase in putrescine concentration in the kindled brain has an inhibitory effect on the development of kindling.