“…DA is found in both peripheral and central tissues; however, concentrations of DA are generally much greater in the CNS than in the periphery. In the periphery, DA is found in: (1) postganglionic adrenergic neurons where in most instances, excepting certain sympathetic n e r v e~, '~ the relative concentration is quite low; (2) the heart,I5 perhaps concentrated in the region of the sino-atrial nodeI6; (3) adrenal glandI7; and (4) other tissues, e.g., mammalian kidney, pituitary gland, lung, bronchi, liver, jejunum, colon, parotid gland, carotid body, and pancreas where it is often associated with noninnervated structures. 's Labeled DA is distributed in peripheral organs of guinea pigs following i.v.…”