C-FOS EXPRESSION IN THE HYPOTHALAMOPITUITARY SYSTEM INDUCED BY ELECTROACUPUNCTURE OR NOXIOUS-STIMULATION

IN the anaesthetized rat, low frequency electrical stimulation of the Zusanli acupoint (S36) or noxious thermal stimulation caused by immers ing the footpad in water at 52 degrees C caused marked expression of c -fos in the anterior lobe of the pituitary gland, as well as in the ar cuate and some nearby hypothalamic nuclei. A similar anterior lobe res ponse was caused by immobilization stress in awake rats but in this ca se Fos-immunoreactive cells extended into the intermediate lobe and we re very abundant in the paraventricular nucleus. It is suggested that the anterior pituitary cells that respond to stress are also activated by acupuncture or painful stimulation. However, the mechanisms of pit uitary cell activation seem distinct from those occurring in stress, s ince different hypothalamic nuclei are involved.