Serotonin-synthesizing nerve fibers in rat and cat cerebral arteries and arterioles: immunohistochemistry of tryptophan-5-hydroxylase.
Nerve fibers synthesizing 5-hydroxytryptamine (5-HT or serotonin) were demonstrated in rat and cat cerebral blood vessels by immunohistochemical localization of the rate-limiting enzyme catalyzing the biosynthesis of 5-HT, namely tryptophan-5-hydroxylase (TPOH). TPOH-immunoreactive fibers were present in all parts of the circle of Willis with a somewhat less intense distribution in the vertebro-basilar segment. Single, small nerve fibers intermingled around the vessel wall were found in both species but clear TPOH-immunoreactive varicosities were observed predominantly in the rat. The most striking observation was the dense network of TPOH-positive fibers innervating some but not all small pial arteries, and, to a lesser extent, pial arterioles. These results provide the evidence that, at least in these species, the cerebrovascular bed is innervated by authentic serotonergic fibers which can synthesize their own 5-HT.
Chédotal
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Laboratory of Cerebrovascular Research, Montreal Neurological Institute, Que., Canada.
Hamel
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D000818:Animals; D001160:Arterioles / Q000294:innervation*; D002536:Cerebral Arteries / Q000294:innervation*; D007150:Immunohistochemistry; D008297:Male; D009412:Nerve Fibers / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000096:biosynthesis*; D014365:Tryptophan Hydroxylase / Q000378:metabolism*
D012701:Serotonin; D014365:Tryptophan Hydroxylase