[Adrenergic neuromuscular junctions in the cerebral arteries of birds]

By means of the histochemical and electron microscopical methods, adrenergic innervation of the middle cerebral artery and its branches have been investigated in three sparrows (Passer montanus), blue rock pigeons (Columba livia), hens (Gallus domestica), hazel-grouses (Tetrastes bonasia), large billed crows (Corvus levaillantii), ducks (Anas domestica) and slaty backed gulls (Larus schistisagus). Neuromuscular connections in all the birds investigated have similar organizational features. Some adrenergic effectors are situated 700 nm from the external layer of myocytes in the vascular middle tunic, and they perform the distant transmission. Other effectors are at the distance of 40-80 nm from myocytes, and they are built according to the synaptic type. They produce certain action upon single muscle cells, thus performing local transmission. For the neuromuscular connections of the cerebral vessels in the birds, presence of multiaxonal complexes is specific. Axons of the complex innervate groups of muscle cells and they are at the distance of 50-270 nm from their plasmic membranes. Perhaps, they combine the local and distant means of transmission.