Peripheral sensory nerve fibers that dichotomize to supply the brachium and the pericardium in the rat: a possible morphological explanation for referred cardiac pain?

Two fluorescent dyes, 'True Blue' and 'Diamidino Yellow' were injected, respectively, into the pericardial sac and into the medial brachial cutaneous nerve or subcutaneously into the medial side of the brachium. Double-labelling was observed in ipsilateral dorsal root ganglia neurons of spinal cord segments C8, T1 and T2, indicating that dichotomizing afferent fibers supply both the pericardium and the brachium. This finding provides a possible morphological explanation for referred cardiac pain.