IMMUNOCYTOCHEMICAL LOCALIZATION OF SUBSTANCE P RECEPTOR IN THE MIDBRAIN PERIAQUEDUCTAL GRAY AND RAPHE NUCLEI OF THE RAT

The immunocytochemical staining technique was used in the present study to investigate the precise localization of the substance P receptor (SPR) in the rat midbrain periaqueductal gray (PAG) and raphe nuclei. Dense SPR-like immunoreactive (SPR-LI) neuronal cell bodies and fibers mainly distributed in the dorsal subdivision, lateral subdivision or ventral subdivision at the rostral, middle or caudal level of the PAG. Dense to moderate density of SPR-LI neuronal cell bodies and fibers were localized in the nucleus linearis, nucleus raphe dorsalis, nucleus raphe median, nucleus raphe pontis, nucleus raphe magnus and nucleus raphe obscurus. Sparse SPR-LI fibers were occasionally seen in the nucleus centralis inferior and nucleus raphe pallidus.