Bilateral innervation of the cerebral arteries by the superior cervical ganglion in cats.

The effect of removal of the left superior cervical ganglion on the contractile response to norepinephrine (NE) and 5-hydroxytryptamine (5-HT, serotonin) was studied in isolated segments of the middle cerebral artery (MCA) and posterior communicating artery (PCoA) of the cat. Fifteen days after the excision, each dose of NE elicited a potentiated response in both the MCA and the PCoA, whichever side they originated. By contrast, 5-HT induced enhanced vasoconstriction at each dose only in the MCA and PCoA from the left side. When segments of MCA and PCoA from the right side were challenged against 5-HT, a significantly increased response was found only at the first three doses. On the other hand, the NE content of pools made of MCA, PCoA, and anterior cerebral artery from each side was reduced to the same level on both sides after ganglion removal. These results indicate that the excised superior cervical ganglion innervated the MCA and PCoA from both sides of the circle of Willis.