ANATOMICAL LOCALIZATION OF IMMUNOREACTIVE OXYTOCIN AND BETA-ENDORPHININ THE BOVINE NEUROINTERMEDIATE LOBE

Background: Beta-endorphin and oxytocin immunocytochemical localizatio n were examined in the neurointermediate lobe (lobus nervosus and pars intermedia) of the bovine hypophysis in order to describe the anatomi cal distribution of these two neurointermediate lobe hormones. Methods : Twenty-seven bovine hypophyses were collected from slaughterhouse an imals (seven mature lactating cows, eleven mature nonlactating cows, t hree nulliparous heifers, and six steers). Hypophyses were immuno-stai ned for oxytocin-containing fibers and beta-endorphin-secreting cells by using the avidin biotin-immunoperoxidase method. The distributions of beta-endorphin-positive cells and oxytocin-positive nerve fibers we re plotted on projected outlines of the hypophyses. Immunoreactive sta ining intensity was graded numerically as weak, moderate, or heavy by three individuals who had no knowledge of the animals' physiological s tatus. Results: Oxytocin immunoreactivity was confined to the lobus ne rvosus while beta-endorphin staining was confined to the pars intermed ia and the pars distalis. However, oxytocin immunopositive neurosecret ory terminals were distributed more heavily in that part of the lobus nervosus bordering the pars intermedia than in the center of the lobe. Conclusions: These results were similar to those previously reported for the rat (Swaab et al., 1975; J. Neural Transm., 36:195-215; Deftos and Catherwood, 1980; Life Sci., 27:223-228). (C) 1994 Wiley-Liss, In c.