KINDLING INDUCES A LONG-LASTING INCREASE IN BRAIN NITRIC-OXIDE SYNTHASE ACTIVITY

GENERALIZED seizures induced by kindling are associated with a long-te rm increase in vasopressin mRNA expression in vasopressin neuroendocri ne cells. Since nitric oxide synthase activity is strongly expressed i n these neurons and may play a role in mechanisms of plasticity, we us ed NADPH-diaphorase histochemistry to examine nitric oxide synthase ac tivity 1 month after amygdala kindling. Both the number of stained neu rons and average intensity of cellular labeling in the supraoptic nucl eus were increased in the kindled rats. In adjacent limbic regions, te rminal-like staining was also increased, suggesting a general elevatio n of limbic nitric oxide synthase activity. Thus, increased nitric oxi de production may play a role in sustaining the increase in vasopressi n mRNA and plastic changes in the amygdala associated with kindling.