Norepinephrine is released from which sites?

Norepinephrine is released from which sites?

• A. Adrenal medulla only
• B. CNS neurons only
• C. Adrenal medulla (20%) & CNS neurons
• D. Sympathetic nerve terminals

Answer: (C)

Norepinephrine is released from both central and peripheral sources. In the brain, noradrenergic neurons in areas like the locus coeruleus release NE as a neurotransmitter at synapses, influencing arousal, attention, and stress responses. Peripherally, sympathetic nerve terminals release NE as the neurotransmitter at target organs. The adrenal medulla, a neuroendocrine organ, also releases catecholamines into the bloodstream, and while it mainly secretes epinephrine, it contributes about 20% norepinephrine. So norepinephrine comes from adrenal medulla (about 20%) and CNS neurons, making that combination the best representation of NE release sites. The sympathetic terminals also release NE, but this option captures both central and adrenal sources.

Norepinephrine is released from both central and peripheral sources. In the brain, noradrenergic neurons in areas like the locus coeruleus release NE as a neurotransmitter at synapses, influencing arousal, attention, and stress responses. Peripherally, sympathetic nerve terminals release NE as the neurotransmitter at target organs. The adrenal medulla, a neuroendocrine organ, also releases catecholamines into the bloodstream, and while it mainly secretes epinephrine, it contributes about 20% norepinephrine.

So norepinephrine comes from adrenal medulla (about 20%) and CNS neurons, making that combination the best representation of NE release sites. The sympathetic terminals also release NE, but this option captures both central and adrenal sources.