Degeneration and regrowth of adrenergic nerves after microvascular anastomosis. A fluorescence histochemical study on end-to-end anastomoses of femoral vessels in the rat.

The normal femoral artery and its branches were found to be innervated with a dense network of adrenergic nerves. The nerve plexus around the vein was sparse. Adventitial stripping of the femoral vessels, with or without division and reanastomosis, caused local disappearance of catecholamine fluorescence in the stripped area. The distal adrenergic innervation remained normal if the femoral nerve was left intact. Division of the femoral nerve, alone or in combination with blood vessel division and reanastomosis, caused total disappearance of catecholamine fluorescence from the adrenergic nerves of the entire distal neurovascular tree examined. At the end of the observation period of 36 weeks from the time of division of the nerve, artery and vein with subsequent microvascular anastomosis, numerous adrenergic nerves were observed to have crossed the suture line. The vascular nerve plexus around the femoral vessels was dense in places, but in other places sparse or absent. It seems that the reinnervation occurs not only over the suture line, but also together with other regenerating nerves from the adjacent tissues and by collateral sprouting from adjacent adrenergically normally innervated areas.

Innervation of syngeneic vein grafts in the rat. The regeneration of cholinesterase positive nerves.

The regeneration of cholinesterase positive nerves into segments of the supradiaphragmatic inferior vena cava transplanted from one rat into the abdominal aorta of another rat of the same inbred strain and sex were studied, using a histochemical thiocholine method for the demonstration of cholinesterase. Iso-OMPA and BW-284 C 51 were used as inhibitors for nonspecific cholinesterase (nsChE) and acetylcholinesterase (AChE), respectively. A total of 12 grafts were examined 3, 5, 8, 16, 27 and 32 weeks after transplantation. One single regenerating nsChE reactive nerve was seen near the suture line in a 3-week-old graft. Some solitary regenerating nerves were regularly seen in the grafts at 5 weeks. Eight weeks after grafting some solitary sparsely distributed nerves were found in the outer layers of the graft. In the 16-, 27-, and 32-week-old grafts, nsChE reactive nerves and small nerve bundles were running either solitary or forming nerve plexa in addition to nerves in the vicinity of vasa vasorum. These regenerated nsChE reactive nerves are probably vasomotor in nature. The AChE reaction showed a clear activity in the intimal layer of the grafted veins. No AChE reactive nerves were seen in the 3-, 5-, and 8-week-old grafts. Only occasional AChE positive nerves were observed 16, 28 and 32 weeks after transplantation. These nerves are probably sympathetic cholinergic nerves.