NEUROPEPTIDE-Y IMMUNOREACTIVITY IN THE PILOCARPINE MODEL OF TEMPORAL-LOBE EPILEPSY

Neuropeptide-Y (NPY) is expressed by granule cells and messy fibres of the hippocampal dentate gyrus during experimental temporal lobe epile psy (TLE). This expression may represent an endogenous damping mechani sm since NPY has been shown to block seizure-like events following hig h-frequency stimulation in hippocampal slices. The pilocarpine (PILO) model of epilepsy is characterized by an acute period of status epilep ticus followed by spontaneous recurrent seizures and related brain dam age. We report peroxidase-antiperoxidase immunostaining for NPY in sev eral brain regions in this model. PILO-injected animals exhibited NPY immunoreactivity in the region of the messy fibre terminals, in the de ntate gyrus inner molecular layer and, in a few cases, within presumed granule cells. NPY immunoreactivity was also dramatically changed in the entorhinal cortex, amygdala and sensorimotor areas. In addition, P ILO injected animals exhibited a reduction in the number of NPY-immuno reactive interneurons compared with controls. The results demonstrate that changes in NPY expression, including expression in the granule ce lls and messy fibres and the loss of vulnerable NPY neurons, are prese nt in the PILO model of TLE. However, the significance of this changed synthesis of NPY remains to be determined.