The distribution of galanin (GAL) and somatotropin-release-inhibiting-factor (SRIF) immunoreactivity in the hypothalamus and pituitary of the sea bream (Sparus aurata) was studied by immunocytochemistry. An extensive system of neurons immunoreactive with antisera to the two peptides was identified throughout the brain with staining particularly in the hypothalamus. In the hypothalamus, GAL immunoreactive perikarya were detected principally in the nucleus preopticus and nucleus tuberis. Major nerve tracts were observed to sweep down from the hypothalamic nuclei and reached the pituitary via the preoptico-hypophysial tract. Many of the fibers had varicose swellings indicating they were secretory. SRIF immunoreactivity was distributed similarly to GAL but the network of nerve fibers was less dense; no colocalization of these two peptides was seen. SRIF immunoreactive perikarya were present in the preoptic nucleus, the tuberal nucleus, and the basolateral hypothalamus. These perikarya were large and densely staining and were predominately bipolar, although some multipolar perikarya were observed. In the pituitary GAL and SRIF immunoreactivities were confined principally to the pars distalis where fibers infiltrated between growth hormone, prolactin, and adrenocorticotrophic cells. More of the fibers were immunoreactive for SRIF than for GAL. There was no immunoreaction for GAL or SRIF in any of the pituitary cells. There is thus morphological evidence for a neuroendocrine control of the pars distalis by GAL and SRIF and for a possible functional interaction between these two systems.

http://www.ncbi.nlm.nih.gov/pubmed/8729936?dopt=Abstract