Acta Pharmacologica Sinica 2007 October; 28 (10): 1550-1558; doi: 10.1111/j.1745-7254.2007.00644.x

Aim: To investigate the effect of clonidine, moxonidine, folic acid, and mecobalamin on arterial baroreflex (ABR) function in stroke-prone spontaneously hypertensive rats (SHR-SP) and the possible mechanisms involved.

Methods: Eighty-one SHR-SP were divided into 7 groups. Four groups were designated for the intragastric (ig) administration of clonidine (1.0 and 10.0 µg/kg), moxonidine (0.1 and 1.0 mg/kg), folic acid (1.0 mg/kg), and mecobalamin (1.0 mg/kg). Three groups were for the intracerebroventricular (icv) injection of clonidine (4 µg/4 µL), moxonidine (5 µg/4 µL), and mecobalamin (20 µg/4 µL). Blood pressure (BP) was recorded in the conscious state for 30 min and baroreflex sensitivity (BRS) was determined respectively before and after drug administration.

Results: Clonidine and moxonidine significantly decreased BP, prolonged the heart period (HP), and increased BRS when administered as either ig or icv injections. Both BP and HP were unchanged by ig folic acid or mecobalamin injection. However, BRS was significantly increased by both.

Conclusion: Clonidine, moxonidine, folic acid, and mecobalamin improved impaired ABR function in SHR-SP. The central mechanism was involved in this effect of either clonidine or moxonidine. Mecobalamin improved ABR function through the peripheral mechanism.

Keywords: clonidine; moxonidine; folic acid; mecoba-lamin; arterial baroreflex; stroke-prone spontaneously hypertensive rats