Effect of clonidine and guanfacine on dopamine and serotonin level in rat brain

ABSTRACT

In the present work, the pattern of dopamine and 5-HT in whole and different areas of brain of Egyptian strain of male albino rats both in normotensive and DOCA and salt hypertensive rats has been determined. Moreover, the effects of two centrally acting antihypertensive drugs, namely clonidine [0.1 mg/kg] and guanfacine [1 mg/kg], have been analyzed using biochemical fluorescent techniques. The findings revealed that in normotensive rats the highest level of dopamine was in the cerebral cortex compared with the midbrain for serotonin. Hypertensive rats showed rise in dopamine level in whole and specified areas of brain. This may be due to increase in dopamine synthesis or inhibition of its release. Serotonin level was also elevated which can be due to enhancement in its synthesis secondary to its influence on other neurotransmitters as well as adaptation to stress. On the other hand, clonidine and guanfacine normalized the dopamine level in hypertensive rats to the values of controls. This may be attributed to increased dopamine release. On the other hand, clonidine and guanfacine increased serotonin level in hind brain possibly due to reduction in its release. This may explain the central hypertensive role of serotonin. The quantitative differences in the action of clonidine and guanfacine can be explained by their relative concentration and effectiveness in different areas of rat brain