An immunohistochemical observation of polypeptides and monoamines in the nucleus preopticus medianus of the rat.

A detailed regional distribution of nerve cells and terminals immunoreactive to polypeptides or monoamines was examined in the 5 subdivisions (rostral, mid-dorsal, mid-ventral, caudo-dorsal and caudo-ventral parts) of the nucleus preopticus medianus (POMe) of the rat. In general, immunoreactive nerve cells and terminals are more numerous in the ventral parts of the middle and caudal POMe. Nerve cells immunoreactive to neurotensin (NT), Met-enkephalin-Arg6-Gly7-Leu8 (mENK8) or cholecystokinin-octapeptide (CCK8) are distributed throughout the POMe, while those immunoreactive to luteinizing hormone-releasing hormone (LHRH) are found in the rostral and middle POMe. Nerve cells immunoreactive to substance P (SP) are seen in the middle and caudal POMe and those immunoreactive to somatostatin (SRIF) are scattered in the middle part of the nucleus. The densities of nerve terminals immunoreactive to neuropeptide tyrosine, mENK8, SP or noradrenaline are high throughout the POMe, while nerve terminals immunoreactive to CCK8, LHRH, NT, SRIF or vasoactive intestinal polypeptide are moderate and those immunoreactive to calcitonin gene-related peptide, serotonin or dopamine are sparse. This varied distributional pattern of immunoreactive nerve cells and terminals suggests regional differences in function within the POMe.