Abstract— The superior cervical sympathetic ganglion of rats contains a finite amount of epinephrine all of which is of ganglionic origin. Treatment of new‐born rats with dexamethasone for 8 days results in a 112‐fold increase in the epinephrine concentration, whereas the norepinephrine and dopamine are increased by only 1·4‐ and 1·9‐fold respectively. This epinephrine increase in newborn rats is reversible if treatment is discontinued, and it fails to occur in adult animals. The epinephrine store of normal and dexamethasone treated animals is resistant to the depletion by reserpine. There is no increase in the epinephrine content in organs innervated by axons emanating from the ganglion. The data presented support the localization of epinephrine in small intensely fluorescent cells in the ganglion and we propose that epinephrine may be released from these cells and function as a modulator of ganglionic transmission.

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