Innervation of arteriovenous anastomoses in the web of the foot of the domestic duck, Anas platyrhynchos: structural evidence for the presence of non-adrenergic non-cholinergic nerves.

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RESUMO

An analysis of the innervation of arteriovenous anastomoses in the web of the foot of the Pekin Duck (Anas platyrhynchos) was compared with the innervation of the right atrium of the duck heart using histochemical, ultrastructural and morphometric techniques, before and after 6OHDA. The presence of intense catecholamine fluorescence and nerve terminals containing typical noradrenergic small dense-cored vesicles, together with the absence of fluorescence and degeneration of noradrenergic terminals after 6OHDA, indicated the presence of a dense adrenergic innervation at the periphery of the anastomoses. Ultrastructural and histochemical data gave support to the presence of a cholinergic innervation. There was evidence that arteriovenous anastomoses were innervated by non-adrenergic, non-cholinergic nerves, viz. after 6OHDA, the mean diameter, mean percentage and mean density of granular vesicles in axon profiles associated with anastomoses (107 . 25 nm, 22 . 34% and 12 . 73 vesicles micron-2, respectively) were significantly higher (P less than 0 . 001) than values in the atrium (87 . 13 nm, 9 . 92% and 5 . 51 vesicles micron-2, respectively) and axons associated with anastomoses contained large granular vesicles ranging up to 210 nm in diameter. This non-adrenergic non-cholinergic innervation may represent the non-adrenergic non-cholinergic vasodilatory nerves shown by pharmacological methods to be present in the foot of the Pekin Duck.

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