Distribution and numbers of indoleamine cell bodies in the cat brainstem determined with Falck-Hillarp fluorescence histochemistry

Abstract

Using the Falck-Hillarp method, the cat brainstem was found to contain approximately 60,000 indoleamine (IA) cells. Most of these (46,000 or 77%) are located within the raphe nuclei. Nissl-stained material demonstrated both medium- and small-sized perikarya in the raphe nuclei, and quantitation revealed that the IA cells comprise only part of the medium-sized cells. Thus, the raphe dorsalis holds about 24,000 IA cells representing some 70% of its medium-sized cells. Corresponding values were for raphe pallidus 8,000 IA cells (55%), raphe centralis superior 7,400 (35%), raphe magnus 2,400 (15%), raphe obscurus 2,300 (33%), linearis intermedius 2,100 (23%), and raphe pontis 280 (9%). A considerable number of IA cells (13,600, representing 23% of the total) were found in locations outside the raphe nuclei: in ventral brainstem as lateral extensions from the raphe, among the bundles of fasciculus longitudinalis medialis, in periventricular gray and adjacent tegmentum, mixing with the noradrenergic cells of the locus coeruleus complex, among the mesencephalic dopamine cells, and in the nucleus interpeduncularis.