Somatostatin-containing neurons in the rat brain: widespread distribution revealed by immunocytochemistry after pretreatment with pronase.

Immunocytochemical staining after controlled proteolytic treatment of the sections with pronase revealed widespread distribution of neuronal cell bodies with somatostatin-like immunoreactivity (SLI) in the rat forebrain. SLI-positive neurons were found in regions of the neocortex, the pyriform cortex, the cingulate cortex, the striatum, the olfactory tract and tubercle, the nucleus accumbens, the septum, and the hypothalamus. These results are consistent with previous radioimmunoassay findings and suggest the presence of large somatostatin-like (possibly precursor) molecules in the neurons stained for SLI after pronase treatment.