[Potentiation of electroacupuncture analgesia on visceral pain by metoclopramide and its mechanism].

The present study was to investigate the effect of metoclopramide (MCP) on electroacupuncture analgesia (EAA) and its mechanism on a rabbit visceral pain model. The results showed that MCP 8mg/kg i.v. could potentiate EAA and prolong the analgesic duration. The potentiation effect could be attenuated by icv apomorphine (APO) (a mixed D1/D2 agonist). The analgesic duration was shortened by icv SKF38393 (a selective D1 agonist) or LY171555 (a selective D2 agonist). Using HPLC-ECD, we also found that the HVA content in CSF significantly increased at 20 min. after electroacupuncture (EA) or MCP 8mg/kg i.v. (P < 0.05), but the change of HVA content was not significant when EA and MCP 8mg/kg i.v. were used together. All these observations indicate that MCP have effects of potentiating EAA and prolonging analgesic duration. These effects are related to the blockade of the central DA receptor. The activations of D1 or D2 receptor is unfavourable to the expression of EA after effect.