Text: A hormone similar to epinephrine, believed to be formed in the muscle cells by nerve impulses. Causes augmentation of blood pressure and heart rate. s. E. A postulated form of sympathin causing excitation and formed by combination of a chemical mediator released at sympathetic nerve endings with a hypothetical substance in excited effector cells. Syn. nor-epinephrine. s. I. A postulated form of sympathin causing inhibition; formed by combination of a chemical mediator released at sympathetic nerve endings with a hypothetical substance in inhibited effector cells. A hormone which acts as a mediator of nerve impulses at sympathetic nerve synapses; now effectively a disused synonym of noradrenaline.

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Source: 165