Question

The alpha-2 receptor is often located presynaptically and binds released norepinephrine to antagonize further transmitter release. What would be the effect of adding an alpha-2 agonist?

A. increased diffusion of NE from the synaptic cleft

B. Decreased NE release from depolarization

C. Decreased Synthesis of NE

D. Increased excitation to the post synaptic cell

E. Increased recycling of NE

Answer 1

B. Decreased NE release from depolarization

Apla2 receptos are G protein coupled receptors. They are primarily located on the presynaptic nerve endings and when activated they cause decrease in the production of intracellular cAMP which in turn leads to inhibition of further release of norepinephrine. Thus alpha2 agonist bind to alpha2 receptors and activates it preventing further release of norepinephrine. Norepinephrine mainly help body to respond to stress and also necessary for arousal. The use of alpha2 agonists block epinephrine release and leads to sedation.