5-HT-containing nerves to major cerebral arteries of the gerbil originate in the superior cervical ganglia.

ABSTRACT

This study has shown that over 95% of the 5-hydroxytryptamine (5-HT)-containing nerves to major cerebral arteries in the gerbil share a common origin with noradrenergic cerebrovascular nerves in the superior cervical ganglia. A small group of 5-HT-containing and noradrenergic nerves to the vessels of the posterior brain circulation had a different origin, which may be either central or peripheral. The pial blood vessels of the gerbil appeared to have no 5-HT-containing nerve supply. The effects of unilateral superior cervical ganglionectomy on 5-HT-containing and noradrenergic nerves to the arteries of the circle of Willis were different. Our results showed total loss of 5-HT-containing nerves on the vessels ipsilateral to the ganglionectomy combined with ca. 50% reductions of nerve density on the vessels of the contralateral side. There were no contralateral reductions of noradrenergic nerve density in parallel experiments although again the ipsilateral side was totally denervated. We suggest that 5-HT-containing cerebrovascular nerves are differently distributed as well as being in some way more sensitive to nerve damage compared to noradrenergic cerebrovascular nerves. The relationship between a combined serotonergic and noradrenergic vasoconstrictor control of large cerebral blood vessels and serotonergic vasodilation of small pial blood vessels is discussed.