[Limbic seizure and ibotenic acid-induced lesions of substantia innominata in cats].

The substantia innominata (SI) contains a lot of cholinergic neurons and mainly project their fibers to the cerebral cortex and to the amygdala. Degenerative lesions were made in the bilateral SI and influences of these lesions upon kainic acid-induced limbic seizure were studied. Eleven adult cats were stereotaxically implanted and 2.5 micrograms of ibotenic acid (IBO) was injected into the bilateral SI in 6 cats (IBO group) and 1 microliter of phosphate buffer (PB) in 5 cats (PB group). All animals were given freedom at least 8 days to recover from the operation. Kainic acid microinjection was made into the left amygdala and electroclinical observation was done. In PB group, the limbic status was elicited and these seizures persisted for about 3 days after the KA injection. Seizures were subsided but interictal discharges were observed at the injected site of the amygdala. Then, limbic seizures reappeared within 10 days and a slowly progressive development of limbic seizure was observed. These seizures developed further. Occasionally, these limbic seizures successively developed and secondarily generalized seizures occurred once or twice a week. Otherwise, their clinical behaviors were normal during the interictal periods. In IBO group, the limbic status were elicited and lasted for about 3 days after the KA injection. Although interictal discharges reappeared at the injected site of the amygdala, successive development of the limbic seizure was not observed. The secondarily generalized seizure never occurred in the IBO group. Histopathological studies revealed circumscribed degenerative changes in the bilateral SI. The KA microinjection into the amygdala resulted stereotyped amygdaloid degenerative lesions in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)