Oxytocin, but not arginine vasopressin is involving in the antinociceptive role of hypothalamic supraoptic nucleus

Our pervious study has demonstrated that the hypothalamic supraoptic nucleus (SON) plays a role in pain modulation. Oxytocin (OXT) and arginine vasopressin (AVP) are the important hormones synthesized and secreted by the SON. The experiment was designed to investigate which hormone was relating with the antinociceptive role of the SON in the rat. The results showed that (1) microinjection of l-glutamate sodium into the SON increased OXT and AVP concentrations in the SON perfusion liquid, (2) pain stimulation induces OXT, but not AVP release in the SON, and (3) intraventricular injection (pre-treatment) with OXT antiserum could inhibit the pain threshold increase induced by SON injection of l-glutamate sodium, but administration of AVP antiserum did not influence the antinociceptive role of SON stimulation. The data suggested that the antinociceptive role of the SON relates to OXT rather than AVP.