A study of the distribution of chromaffin-positive (CH+) and small intensely fluorescent (SIF) cells in sympathetic ganglia of the rat at various ages.

Small intensely fluorescent (SIF) and chromaffin-positive (CH+) cells were independently investigated by formol-induced fluorescence and by chromaffin techniques in the superior cervical, thoracic and coeliac-mesenteric ganglia of neonatal (2--10 days), adolescent (2--4 months) and adult (6--15 months) rats. Identification of CH+ cells was facilitated by glutaraldehyde fixation prior to chromatin. Intraganglionic blood vessels were displaced by antemortem injection of either India ink or the fluorescent dye Thioflavine-S. SIF and CH+ cells were randomly distributed through the ganglia, either singly or in pairs related to principal neurons, or in variably-sized, highly vascularized groups. In chromaffin preparations these groups either consisted entirely of CH+ cells or else they contained a mixture of CH+ and CH- cells. CH+ cells were present in some adolescent and adult ganglia of all types, and in the neonatal coeliac-mesenteric ganglion at 10 days. In neonatal material generally, SIF cells were mostly green fluorescent, occurring separately or in homogeneous or mixed groups, but both yellow and green cells occurred in coeliac-mesenteric ganglia at 10 days. All ganglia in adolescent and older animals contained both yellow and green cells. There were more green than yellow cells, and more SIF than CH+ cells in all ganglia studied.