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

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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.