How can adrenaline strengthen memories if it does not cross the blood-brain barrier? · Grey Matter

Adrenaline released during an emotional or stressful event binds beta-adrenergic receptors on the sensory fibres of the vagus nerve.

How can adrenaline strengthen memories if it does not cross the blood-brain barrier?

Adrenaline released during an emotional or stressful event binds beta-adrenergic receptors on the sensory fibres of the vagus nerve. The vagus carries the signal to the nucleus of the solitary tract in the brainstem, which activates the locus coeruleus, and noradrenaline is then released in the amygdala and other regions involved in storing memories. In the work of McGaugh and colleagues, adrenaline given after training improves later memory in rats and humans, and blocking beta receptors in the amygdala or cutting the vagal route removes the effect. The body's alarm thus marks a moment as worth keeping without the hormone ever entering the brain.