SOMATOSTATIN, NEUROPEPTIDE-Y, NEUROKININ-B AND CHOLECYSTOKININ IMMUNOREACTIVITY IN 2 CHRONIC MODELS OF TEMPORAL-LOBE EPILEPSY

Somatoslatin-, neuropeptide Y-, neurokinin B- and cholecystokinin-cont aining neurons were investigated in the rat hippocampus in two chronic models of temporal lobe epilepsy, i.e. 30 days after rapid kindling o r electrically induced status epilepticus (post-status epilepticus). A fter rapid kindling, somatostatin immunoreactivity was strongly increa sed in interneurons and in the outer and middle molecular layer of the dentate gyrus. In four of six post-status epilepticus rats (status ep ilepticus I rats), somatostatin immunoreactivity was slightly increase d in the dorsal but decreased in the ventral dentate gyrus and molecul ar layer. Somatostatin immunoreactivity decreased in neurons of the do rsal hilus in the two other post-status spilepticus rats investigated, while a complete loss was found in the respective ventral extension ( status epilepticus-II rats). These changes were associated with a diff erent extent of neurodegeneration as assessed by Nissl staining. Simil arly, neuropeptide Y immunoreactivity was enhanced in neurons of the h ilus and in the middle and outer molecular layer of the dentate gyrus in the dorsal hippocampus of rapidly kindled and status epilepticus-I rats. Neuropeptide Y and neurokinin B immunoreactivity was enhanced in the messy fibers of all post-status epilepticus rats, but not in the rapidly kindled rats. In status epilepticus-II rats, neuropeptide Y-an d neurokinin B-positive fibers were also detected in the infrapyramida l region of the stratum oriens of CA3 and in the inner molecular layer of the dentate gyrus in the dorsal and ventral hippocampus respective ly, labeling presumably sprouted messy fibers. Increased staining of n europeptide Y and neurokinin B was found in the alveus after rapid kin dling. Cholecystokinin immunoreactivity was markedly increased in the cerebral cortex, Ammon's horn and the molecular layer of the dentate g yrus in the ventral hippocampus of rapidly kindled and post-status epi lepticus rats. The lasting changes in the immunoreactive pattern of va rious peptides in the hippocampus may reflect functional modifications in the corresponding peptide-containing neurons. These changes may be involved in chronic epileptogenesis, which evolves in response to lim bic seizures.