ACTIVATION OF ANTERIOR LOBE CORTICOTROPHS BY ELECTROACUPUNCTURE OR NOXIOUS-STIMULATION IN THE ANESTHETIZED RAT, AS SHOWN BY COLOCALIZATION OF FOS PROTEIN WITH ACTH AND BETA-ENDORPHIN AND INCREASED HORMONE-RELEASE

A marked expression of the c-fos proto-oncogene has been recently repo rted in cells of the anterior lobe of the pituitary gland in rats subj ect to electroacupuncture or noxious thermal stimulation under pentoba rbital anaesthesia. The present study was undertaken to identify the a ctivated pituitary cells. Following both kinds of stimulation, most Fo s-immunoreactive anterior robe cells showed colocalization with adreno corticotropic hormone or beta-endorphin immunoreactivity. No c-fos exp ression occurred in pituitary cells immunoreactive for growth hormone, prolactin, luteinizing hormone, or thyrotropin-stimulating hormone. A marked rise of adrenocorticotropic hormone and beta-endorphin concent rations occurred in plasma. In the hypothalamus, c-fos expression was increased in the mediobasal nuclei-namely, the arcuate nucleus-and in the paraventricular nucleus, but more in the former. It is suggested t hat somatosensory noxious input, or the partly noxious input evoked by electroacupuncture, activate the hypothalamo-pituitary-adrenocortical axis as in common forms of stress, but with a specific activation of the mediobasal hypothalamic nuclei and no stimulation of intermediate robe cells. Opiate release from the pituitary gland may contribute to acupuncture analgesia or the intrinsic antinociceptive reactions trigg ered by noxious stimulation.