Comparative distribution of somatostatin, LH-RH, neurophysin, and α-endorphin in the rainbow trout: An immunocytological study

Using immunofluorescence, evidence of a somatostatin (SRIF)-like antigen has been found in the brain and digestive tract of rainbow trout. In the diencephalon, periventricular SRIF immunoreactive hypendymocytes are located in the region dorsal to the nucleus preopticus (NPO). SRIF immunoreactive perikarya are concentrated anterior to the NPO in the nucleus preopticus periventricularis, scattered in small cells in the nucleus lateralis tuberis (NLT) pars anterior, and in a few cells located in an unnamed nucleus in the dorsomedial hypothalamus. In the pituitary SRIF immunoreactive material is located in the neurohypophysial tissue in the proximal pars distalis. In the gut, SRIF cells have been found in the endocrine pancreas and in the gastric mucosa. Comparatively, material immunoreactive for luteinizing hormone-releasing hormone has the same distribution in the pituitary as SRIF, whereas neurophysin immunoreactivity was found in only the neurophysial tissue of the neurointermediate lobe. A few cells reacting with anti-α-endorphin were seen in the NLT in the pituitary stalk region. All the pars intermedia cells in the neurointermediate lobe react with anti-α-endorphin.