Study On The Mechanism Of Central Imidazoline-1 Receptors In The Cardiovascular Regulation

The roles of central imidazoline-1 receptors (I1R) in regulating the cardiovascular activity and mediating the central hypotensive mechanism of clonidine (Clo) are not fully understood. The present study is designed to investigate the role of I1R and NMDA receptors within the ventrolateral medulla in central cardiovascular effects of Clo by the methods of microinjection, iontophoresis in anesthetized rats. It was found that blockade of I1R in the caudal ventrolateral medulla (CVLM) not only decreased the basal blood pressure and barosensitivity, but also completely abolished Clo-induced cardiovascular actions. Furthermore, we found that blockade of NMDA receptors within the rostral ventrolateral medulla (RVLM) effectively antagonized the depressor action and the inhibitory effect of the RVLM presympathetic neurons evoked by Clo. It is concluded that I1R in the CVLM plays an important role in regulating the cardiovascular activities and mediating the clonidine-induced cardiovascular actions. NMDA receptors in RVLM contribute to the central depressor mechanism of Clo.