TRIGEMINAL SENSORY INNERVATION ON PERFORATORS OF THE CIRCLE OF WILLISIN RABBITS BY WHEAT-GERM AGGLUTININ-CONJUGATED HORSERADISH-PEROXIDASEANTEROGRADE TRACING

Distribution patterns of sensory innervation from the trigeminal gangl ion to the perforators of the circle of Willis in rabbits were investi gated by wheat germ agglutinin-conjugated horseradish peroxidase (WGA- HRP) anterograde tracing. Twenty Japanese white rabbits were anestheti zed by inhaling 1% halothane. Using a microsurgical technique, 4 mu l of 2% WGA-HRP in 1 M KCl solution, colored with brilliant blue, was mi cro-injected into the medial part of the left trigeminal ganglion in 1 4 animals with a pressure injection system. Another six served as cont rols to exclude the possibility of labeling non-trigeminal axons. Fort y-eight hours later, the perforators in the cisternal and intracerebra l segments along with their parent arteries were dissected from the br ain according to Dacey's dissecting technique after transcardial perfu sion, reacted with the 3,3',5,5'-tetramethyl benzidine method of Mesul am. The results revealed that sensory nerves on the perforators of the circle of Willis were less densely innervated than those on their par ent arteries due to the difference in diameter. The posteromedial perf orating arteries arising from the P1 segment of the posterior cerebral artery to the tegmentum, posteroventral thalamus and posterior hypoth alamus were more prominently and consistently innervated than other pe rforators. The sensory fibers were seen on the cisternal segment of th e perforating arteries. A parallel or twisted pattern was found in the perforators less than 100 mu m in diameter, while a meshwork pattern was visualized in the proximal part of some bigger ones. Fine sensory fibers could be traced on the perforators as small as 40 mu m in diame ter. The present study demonstrates for the first time the detailed di stribution patterns of sensory nerves from the trigeminal ganglion to perforators of the circle of Willis in rabbits. Pathophysiological imp lications of the findings are discussed in relation to cerebral vasosp asm following subarachnoid hemorrhage.