Immobilization stress affects oxytocin and vasopressin levels in hypothalamic and extrahypothalamic sites.

Oxytocin (OT) and vasopressin (VP) have been localized in various sites within the central nervous system outside the classic hypothalamo-neurohypophyseal axis. This study investigated the effect of immobilization stress on the levels of OT and VP in the hypothalamus, pons-medulla, and the cervical, thoracic, and lumbosacral segments of the spinal cord. Male Long Evans rats were immobilized for 1 min and sacrificed by guillotine. The tissues were dissected out and homogenized in 0.1 N HCl. The hormone content was determined by radioimmunoassay (RIA) in Sep-pak extracted samples. The data show a decrease in OT content of 33.6% (P < 0.02) and 42.4% (P < 0.01) in the hypothalamus and pons-medulla, respectively. In the spinal cord, however, OT levels were increased by 39.1% (not significant), 51.1% (P < 0.05), and 87.6% (P < 0.001) in the cervical, thoracic, and lumbosacral segments respectively. The VP content of the hypothalamus and pons-medulla did not change. However, in the spinal cord, the VP content was also increased by 101.4% (P < 0.01) and by 143.7% (P < 0.01) in the cervical and lumbosacral segments. The levels of VP in the thoracic segment did not change. The data demonstrate that stress can alter hypothalamic and extra-hypothalamic levels of OT as well as spinal cord levels of VP. The exact physiological effects of these changes, particularly within the spinal cord, remain to be elucidated.