Sympathectomy provides evidence of dopamine storage in rat laryngeal nerve paraganglia

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Abstract
Catecholamine content in the recurrent and superior laryngeal nerves (RLN and SLN) of the rat was analysed by high‐performance liquid chromatography after surgical and chemical sympathectomy. Sympathectomy induced by repeated injections of guanethidine did not lead to any change in the dopamine (DA) level, whereas the noradrenaline (NA) content decreased by 68% and 64% respectively in the RLN and SLN. Surgical excision of the superior cervical ganglion (SCG) did not alter the level of DA in the SLN, but caused a 60% decrease of DA in the RLN. Removal of SCG did not affect the NA levels either in the RLN or in the SLN, unless it was combined with extirpation of the middle cervical ganglion, which induced a decrease in NA in both nerves. The results indicate that much of the DA in the laryngeal nerves is stored outside the sympathetic nerve fibres, probably in the small organs earlier characterized as endoneurial paraganglia.