ALTERED BRAIN CONTENTS ON NEUROPEPTIDES IN SPONTANEOUSLY EPILEPTIC RATS (SER) AND TREMOR RATS WITH ABSENCE SEIZURES

Immunoreactive- (IR-) somatostatin (SRIF), neuropeptide Y (NPY) and co rticotropin-releasing factor (CRF) contents were investigated in the b rain of tremor rats with absence-like seizure and Spontaneously epilep tic rats (SER), which is a genetically defined double-mutant (zi/zi, t m/tm) obtained by mating titter homozygote (zi/zi) with tremor heteroz ygote (tm/+) and shows both absence-like seizure and tonic convulsions . Increased levels of IR-NPY and IR-CRF were observed in several regio ns including the amygdala and hippocampus in homozygous SER compared t o heterozygous SER (zi/zi, tm/+ or +/+); Homozygous tremor rats (tm/tm ) showed lower levels of IR-NPY and IR-CRF contents mainly in the hipp ocampus and mesolimbic system (entorhinal and pyriform cortex and nucl eus accumbens) than heterozygous tremor rats. IR-SRIF contents of homo zygous SER were higher in frontal cortex than heterozygous SER and in amygdala than homozygous tremor rats. No change of IR-SRIF between. gr oups was noted in the hippocampus among brain structures underlying ep ileptogenicity. The results suggest that the change of neuropeptide le vels, most conspicuous in NPY among three peptides tested, may be invo lved in the phenotypical manifestation of seizures in SER-and tremor r ats, and that the development of tonic convulsion and absence seizures may be differently associated with the change of brain neuropeptide l evels.