Somatostatin- and neuropeptide Y-synthesizing neurones in the fascia dentata of humans with temporal lobe epilepsy

We used in situ hybridization techniques to study the distribution of neuro nes synthesizing somatostatin mRNA and neuropeptide Y mRNA in the hilar reg ion of the hippocampal formation of patients with temporal lobe epilepsy. I n the dentate gyrus, somatostatin mRNA- and neuropeptide Y mRNA-synthesizin g neurones were found to be exclusively located within the hilar region. Un like animal models, no ectopic expression of either peptide was found in pr incipal cells. The numbers of hilar interneurones expressing somatostatin m RNA and neuropeptide Y mRNA were compared with the degree of hilar cell los s determined by immunohistochemistry against neuronal nuclear antigen. The numbers of somatostatin and neuropeptide Y mRNA-synthesizing neurones varie d considerably between patients, but both were found to be highly correlate d to the total number of neuronal nuclear antigen-immunoreactive hilar neur ones. These results suggest that loss of somatostatin and neuropeptide Y in terneurones occurs in proportion to overall hilar cell loss, and therefore the hypothesis of a selective loss of these interneurones in temporal lobe epilepsy seems unlikely.