Clonidine hypotension in spontaneously hypertensive rats (SHR) depends on the functional state of GABAergic and glutamatergic systems.

The effect of gamma-aminobutyric acid (GABA)A receptors and of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor blockade on clonidine hypotension was studied. The experiments were performed on spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. We found that the blockade of GABAA receptors line significantly (P < 0.01) reduced hypotensive responses to clonidine. Similarly, the NMDA receptor antagonist dizocilpine (MK-801) completely abolished the blood pressure lowering effect of clonidine. Our findings support the conclusion that clonidine hypotension is closely related to the functional state of both inhibitory GABAergic and excitatory glutamatergic systems.