Changes of somatostatin and vasoactive intestinal polypeptide immunoreactive neurons in rat cerebral cortex with seizures induced by kainic acid

We have examined the amount and distribution of the neuropeptides somatostatin (SMT) and vasoactive intestinal polypeptide (VIP) in the cerebral cortex of rats, during and after limbic seizures induced by peritoneal injection of kainic acid (KA) and the distributions of those neuropeptides in the cortical areas in controls. Two days after injection, pronounced decreases in SMT and VIP immunoreactive neurons (INs) were observed throughout the cerebral cortex. This early decrease in peptide levels may result from increased release and subsequent inactivation of the peptides due to limbic seizure. Six days after injection of KA, the decreased SMT- and VIP-neuroreactive neurons recovered partially. They recovered to normal on day 10. This result suggested that normalization of cerebral function can be seen about 10 days after seizure. Distributions of SMT-INs and VIP-INs in normal control rats were markedly different in the various cortical areas. As a whole, SMT-INs in the isocortex were more numerous than those in the allocortex. VIP-INs were abundantly distributed in the allocortex as well as in the isocortex.