Arginine vasopressin in hypothalamic paraventricular nucleus is transferred to the caudate nucleus to participate in pain modulation

Arginine vasopressin (AVP), which is synthesized and secreted in the hypothalamic paraventricular nucleus (PVN), is the most important bioactive substance in the pain modulation. Our pervious study had shown that AVP plays an important role in pain modulation in caudate nucleus (CdN). The experiment was designed to investigate the source of AVP in CdN by the nucleus push-pull perfusion and radioimmunoassay. The results showed that: (1) pain stimulation increased the AVP concentration in the CdN perfusion liquid, (2) PVN decreased the effect of pain stimulation which was stronger in both sides than in one side of PVN cauterization; and (3) L-glutamate sodium would excited the PVN neurons by the PVN microinjection that could increase the AVP concentration in the CdN perfusion liquid. The data suggested that AVP in the CdN might come from the PVN in the pain process, i.e., AVP in the PVN might be transferred to the CdN to participate in the pain modulation.