Role of opioid peptides and subfornical organ in the renal function of intact and hypophysectomized rats

An inhibitory effect on water, sodium and potassium excretion occurs after both systemic and central injections of morphine, beta-endorphin and other opioid peptides. Some investigators claimed that antidiuretic hormone release could be a mechanism explaining opioid-induced oliguria. Injection into the subformical organ of a synthetic Met-enkephalin analog (FK 33824) reduced urine outflow as well as renal Na + and K + excretion. Identical effects were observed in hypophysectomized or in median eminence-lesioned rats. In addition, no changes were seen in blood pressure after FK 33824 injection into the subfornical organ. These results suggest that opioid stimulation of this structure induces an inhibitory effect on renal water, Na + and K + excretion, and that antidiuretic hormone release is probably not important to these phenomena.