Effect of a single dose of clonidine and guanfacine on the content of norepinephrine and GABA in rat brain

ABSTRACT

This work aimed at studying the pattern of GABA and norepinephrine in Egyptian strain of male albino rats in normotensive and DOCA/ Salt hypertensive rats. Moreover, the effect of two centrally acting antihypertensive drugs namely clonidine and quanfacine upon the contents of neurotransmitters in whole brain as well as cerebral cortex, thalamus and hypothalamus, mid brain and hind brain was investigated. The data revealed that, the highest levels of norepinephrine and GABA were in hind brain of normotensive rats. Hypertensive rats showed significant increase in norepinephrine concentration in whole brain and specified areas.The concentration of GABA in hind brain of DOCA/Salt hypertensive rats was significantly raised. On the other hand, it was significantly decreased in other areas of brain. The agonistic effect of clonidine caused a significant rise in norepinephrine concentration in hind brain. Other brain areas showed significant decrease. The findings in the work showed that guanfacine is a weaker agonist than clonidine as it failed to raise norepinephrine concentration in hind brain. This may explain the lack of sedation after guanfacine treatment, while clonidine has a powerful sedative effect