A chemical signal that has both endocrine and neural roles is Epinephrine. Cortisol. Calcitonin. Melatonin.

Epinephrine is released by sympathetic postganglionic neurons (the adrenergic neurons) and serves as neurotransmitter. Epinephrine also serves as emergency hormone of adrenal medulla and prepares body for fight or flight response by intensifying the effect of sympathetic stimulation. Correct answer is A.