The arrangement of neurosecretory and catecholamine fibres in relation to the pituitary intermedia cells of the skate,Raja radiata

Summary The innervation pattern of the intermediate lobe of the skate (Raja radiata) was studied with histological and fluorescence histochemical methods. Neurosecretory fibres, stained with i.a. pseudo-iso-cyanine, were found running in bundles in the central parts of the cell cords. They terminated partly around the perinuclear parts of the intermedia cells, partly around the apices of the cells close to the vascular walls.A catecholamine innervation of the intermedia was also established. Catecholaminecontaining fibres with the appearance of nerve terminals were found around the intermedia cell apices close to the vessels. In some specimens, catecholamine fibres also seemed to terminate at the perinuclear parts of the cells.Thus it is possible, judging solely from structural relations, that both the cell body (the synthesis pole) and the cell apex (the release pole) receive a dual innervation. Recent experimental evidence indicates that the release of MSH from the pars intermedia is controlled by catecholamine fibres, but as yet there is only structural evidence for a special control of hormone synthesis.This study was supported by grants from the Swedish Natural Science Research Council (No. 99-35 and 2126-2) and was carried out within a research organization sponsored by the Swedish Medical Research Council (Projects No. B70-14X-712-05 and B70-14X-56-06).