noradrenaline (norepinephrine)

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noradrenaline (norepinephrine)

the best known neurotransmitter at postganglionic sympathetic nerve endings (ATP and neuropeptide Y are also released). Also secreted into the blood stream from the adrenal medulla in response to activation of the sympathetic nervous system. Acts on all types of adrenoceptors but is less potent than adrenaline at the β2 adrenoceptors that dilate skeletal muscle arteries and airways. Actions include vasoconstriction, relaxation of gut musculature, dilatation of the pupils. Both noradrenaline and adrenaline (to a much lesser extent) are neurotransmitters in the central nervous system.