DISTRIBUTION OF SECRETONEURIN-LIKE IMMUNOREACTIVITY IN COMPARISON WITH SUBSTANCE P-LIKE AND ENKEPHALIN-LIKE IMMUNOREACTIVITIES IN VARIOUS HUMAN FOREBRAIN REGIONS

The distribution of secretoneurin-like immunoreactivity, a peptide der ived from secretogranin II, was studied by means of immunocytochemistr y and compared to the pattern of staining for substance P- and enkepha lin-like immunoreactivities in the human basal forebrain, with special reference to the basal ganglia. Secretoneurin-like immunoreactivity w as characterized by gel filtration and reversed-phase high pressure li quid chromatography analysis. Chromatographic analysis revealed a sing le peak for secretoneurin-like immunoreactivity. No secretoneurin-immu nopositive forms of high molecular weight were found. Secretoneurin-li ke immunoreactivity appeared mainly in dot- and fibre-like structures. In addition, a band-like terminal staining (woolly fibres) that has b een shown by others for substance P- and enkephalin-like immunoreactiv ities, was also observed for secretoneurin-like immunoreactivity. Medi um-sized cells were found arranged in clusters or singly within the ca udate and putamen. In the basal ganglia, a high density of secretoneur in-like immunoreactivity was found in the internal segment of the glob us pallidus, the ventral pallidum and in the pars reticulata of the su bstantia nigra. In these areas the immunostaining appeared mainly as w oolly fibres. The bed nucleus of the stria terminalis and medial amygd ala displayed a high density of fine beaded secretoneurin-like immunor eactive fibres, sometimes forming pericellular contacts. The nucleus b asalis of Meynert was highly innervated by secretoneurin-like immunore active fibres, mainly in the form of woolly fibres. In general, a larg e overlap was found between secretoneurin- and substance P-like immuno reactivity in all examined areas of the basal ganglia. In the bed nucl eus of the stria terminalis and medial amygdala secretoneurin-like imm unoreactivity was distributed very similarly to enkephalin-like immuno reactivity. These data provide evidence that in different subsets of n eurons and neuronal pathways secretoneurin-like immunoreactivity coexi sts with substance P- and enkephalin-like immunoreactivity in several areas of the human brain.