[Histochemical and electron microscopic characteristics of effector nerve endings of avian cerebral arteries].

Neural plexus in arteries at the cerebral basis in the hen and pigeon were studied by means of Koelle's and Falck's histochemical methods and electron microscopically. Periadventitial fasciculi in the cerebral arteries, 14.1+/-1.4 mkm in the diameter contain up to 100+/-11 unmyelinated and 3--5 myelinated fibres. In finer (6.8+/-1.3 mkm) adventitial branches preterminal axons having microtubules, neurofilaments and mitochondria are constantly present. The number of axons in these branches is 18+/-4, with the diameter of each axon being no more than 0.1+/-0.3 mkm. The terminal neural plexus in the arteries of the avian cerebral basis include: a) cholinergic axons with small transparent vesicles, 54+/-7 nm in the diameter; b) adrenergic axons with small (25--30 nm) and large electronopaque vesicles (88+/-9 nm); c) purinergic axons with large granular vesicles, 134+/-11 nm in the diameter.