Contribution of the Supra-Optic Nucleus to Brain and Pituitary Pools of Immunoreactive Vasopressin and Particular Opioid Peptides, and the Interrelationships between These, in the Rat

Abstract

Discrete, bilateral, radiofrequency destruction of the supraoptic nucleus resulted in a parallel fall in levels of immunoreactive (ir) dynorphin (DYN), ir-.alpha.-neo-endorphin (.alpha.-NE) and ir-vasopressin (VP) in the hypothalamus, neurointermediate lobe (NIL) of the pituitary and septum of rats, whereas in the medulla/pons, midbrain and anterior lobe (AL), levels of these peptides were not significantly changed. The content of ir-.beta.-endorphin (.beta.-EP), was in contrast, elevated in the hypothalamus and unchanged in the NIL and AL, while that of ir-met-enkephalin (ME) was modified in neither the hypothalamus nor medulla/pons. As evaluated in lesioned and sham rats, collectively, hypothalamic levels of ir-DYN, ir-.alpha.-NE and ir-VP were positively correlated with their counterparts in the NIL but not, with the exception of ir-VP, with those in the AL. Ir-.beta.-E did not show these relationships. Within the NIL and in the hypothalamus, levels of ir-DYN, ir-.alpha.-NE and ir-VP were positively correlated with each other and independent of those of ir-.beta.-EP and ir-ME. In the AL and other brain tissues, however, only those of ir-DYN and ir-.alpha.-NE were positively and significantly correlated in contrast to ir-VP. Further, across all structures, although the ratio of levels of ir-.alpha.-NE to ir-DYN was quite constant, that of ir-VP to ir-DYN varied enormously. The supraoptic nucleus may contribute to NIL, hypothalamic and septal but not to AL, midbrain or medulla/pons pools of ir-VP, ir-DYN and ir-.alpha.-NE, and it interacts with those of ir-.beta.-EP in the hypothalamus. In the NIL and hypothalamus, ir-DYN, ir-.alpha.-NE and ir-VP are, as compared to ir-.beta.-EP and ir-ME, closely interrelated. AL pools of DYN and ir-.alpha.-NE are closely coupled but, in contrast to NIL pools, not related to ir-VP and independent of the hypothalamus. Extrahypothalamic brain pools of ir-DYN and ir-.alpha.-NE may not be related to ir-VP. The possible existence of ir-DYN and ir-.alpha.-NE independently or ir-VP in the AL and extrahypothalamic nervous tissue is discussed.