Possible involvement of nitric oxide in the inhibition of gastric emptying induced by intracerebroventricular administration of clonidine in conscious rat

Introduction: Our previous findings showed that both clonidine and oxymetazoline inhibited gastric emptying given subcutaneously. The question was raised whether activation of central α2-adrenoceptors are involved also in gastric emptying in conscious rats.

Methods: Male Wistar rats were used. Gastric emptying was measured by phenol red method. Briefly, 1 hour after 1.5ml phenol red solution given orally animals were killed, their stomachs were removed and the amount of the color remained in the stomach were determined photometrically. Drugs were given subcutaneously (sc.), intravenously (iv.) and intracerebroventricularly (icv.).

Results: 1. Both clonidine (ED30=5.93µmol/kg, sc.) and oxymethazoline (ED30=3.25µmol/kg, sc.) inhibited gastric emptying in a dose dependent manner. 2. Both hexamethonium (10mg/kg iv.) and NG-nitro-L-arginine (L-NNA) (15mg/kg iv.) inhibited gastric emtying and reduced the inhibitory effect of clonidine (38 nmol/rat icv.) on gastric emptying.

Conclusion: The inhibitory effect of centrally-injected clonidine on gastric emptying might be due to vagally mediated nitric oxide release.

The work was supported by grants OTKA T 032607 and ETT 389/2003.