Isotonic and hypertonic saline act as stressful stimuli for oxytocinergic system of the pituitary, hypothalamus and spinal cord.

We have recently demonstrated that immobilization stress leads to an increase in the spinal cord oxytocin content in the rat. The current experiments were undertaken to determine if other stressors have similar effect on the spinal cord oxytocin levels. Male Long Evans rats were injected either with isotonic or hypertonic saline and sacrificed either 15 minutes or 3 hours after saline injection. Oxytocin content of the neurohypophysis, hypothalamus and spinal cord were determined by specific radioimmunoassay in Sep-pak extracted samples. The results demonstrate that both isotonic and hypertonic saline act as stressful stimuli and reduce oxytocin content of the pituitary and hypothalamus when the rats were sacrificed within 15 minute following the injection. Spinal cord oxytocin content was also affected by isotonic and hypertonic saline administration; oxytocin content decreased if rats were sacrificed after a short period (15 min) and increased if rats were sacrificed after a long period (3 hours). These results, together with those reported earlier, support the hypothesis that stressors, in general, affect the spinal cord oxytocin content.