Arginine vasopressin induces rat caudate nucleus releasing acetylcholine to participate in pain modulation

A lot of studies have pointed that acetylcholine (Ach), a classic neurotransmitter can regulate pain process in the caudate nucleus (CdN). Our previous report has proven that arginine vasopressin (AVP) effects on pain modulation in the CdN. The communication was designed to investigate the interaction between AVP and Ach in the rat CdN during the pain process. AVP concentration was determined by radioimmunoassay (RIA) and Ach concentration by high performance liquid chromatography (HPLC). The results showed that pain stimulation increased both AVP and Ach concentrations in the CdN perfusion liquid; AVP increased Ach concentration in the CdN perfusion liquid, while AVP receptor antagonist including d(CH2)5Tyr(Me)AVP (V1 receptor antagonist) and d(CH2)5[D-Ile2, Ile4, Ala-NH29]AVP (V2 receptor antagonist) decreased Ach concentration in the CdN perfusion liquid. The data indicated that the analgesic effect of AVP might be involved in the Ach system in the CdN.