Effects of transcutaneous nerve stimulation on the plasma and CSF concentrations of beta-endorphin and the plasma concentrations of ACTH, cortisol and prolactin in hysterectomized women with postoperative pain]

Plasmatic and cerebrospinal fluid levels of beta-endorphin and plasmatic concentration of ACTH, cortisol, and prolactin were investigated in 10 healthy volunteers free of pain and in a group of 38 patients who presented moderate or intense postoperative pain. The analgesic technique was transcutaneous neural stimulation. In 28 patients the stimulation was delivered at 40-80 Hz (high frequency) whereas in the remaining 10 patients it was administered in a placebo form. Measurements of hormone concentrations were performed using radioimmunoassay techniques. In patients free of pain hormone analysis was done at once, whereas in patients with pain this analysis was performed before and one hour after transcutaneous neural stimulation. We compared data obtained in control subjects with data collected in patients before and one hour after high frequency and placebo transcutaneous neural stimulation. Levels of beta-endorphin were comparable in patients with and without pain. However, ACTH, cortisol, and prolactin were increased in patients with pain. High frequency stimulation induced greater beta-endorphin levels than placebo neural stimulation and slightly lower concentration of prolactin. There were no significant differences in ACTH and cortisol levels.