What is the primary presynaptic effect of alpha-2 agonism?

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Multiple Choice

What is the primary presynaptic effect of alpha-2 agonism?

Explanation:
Alpha-2 receptors on sympathetic nerve terminals act as autoreceptors to dampen norepinephrine release. When activated, they couple to Gi proteins, which inhibit adenylyl cyclase and reduce cAMP, leading to decreased calcium influx and less vesicle fusion. The result is a net decrease in norepinephrine released into the synapse, lowering sympathetic signaling. Bronchodilation is mainly a beta-2 effect, not a direct presynaptic action of alpha-2 agonism, and stating no effect or increased release doesn’t fit the autoreceptor mechanism.

Alpha-2 receptors on sympathetic nerve terminals act as autoreceptors to dampen norepinephrine release. When activated, they couple to Gi proteins, which inhibit adenylyl cyclase and reduce cAMP, leading to decreased calcium influx and less vesicle fusion. The result is a net decrease in norepinephrine released into the synapse, lowering sympathetic signaling. Bronchodilation is mainly a beta-2 effect, not a direct presynaptic action of alpha-2 agonism, and stating no effect or increased release doesn’t fit the autoreceptor mechanism.

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