Serotonin-induced constriction of ocular arteries in atherosclerotic monkeys. Implications for ischemic disorders of the retina and optic nerve head
S. S. Hayreh, D. J. Piegors and D. D. Heistad
Department of Ophthalmology, University of Iowa College of Medicine, Iowa City, USA.
BACKGROUND: Ischemic disorders of the retina and optic nerve head, which
constitute a common cause of visual loss, are usually seen in patients with
atherosclerosis. OBJECTIVE: To test the hypothesis that serotonin, which is
released when platelets aggregate, may produce vasospasm in atherosclerotic
monkeys and, thus, may contribute to the ischemic disorders and that
short-term dietary treatment of atherosclerosis causes the propensity to
vasospasm to subside. METHODS: We studied the response of retinal and
posterior ciliary circulation to serotonin in 18 atherosclerotic (25 eyes)
and 5 normal (8 eyes) cynomolgus monkeys. The eyes were evaluated by color
fundus photography and fluorescein fundus angiography. The eyes were
examined under basal conditions and, at a different time, during the
intravenous infusion of serotonin. In 6 of the 18 atherosclerotic animals,
the evaluation was repeated 5 to 12 months after discontinuing the
atherogenic diet (ie, the regression group). RESULTS: Serotonin had no
effect in normal monkeys. In 18 atherosclerotic monkeys, serotonin produced
transient occlusion or delayed filling of the central retinal artery and/or
posterior ciliary artery (PCA) in 9 eyes of 9 animals, involving the
central retinal artery in 5, lateral PCA in 8, and medial PCA in 5, in
various combinations. In 6 animals (6 eyes) of the regression group, the
vasoconstrictor effect of serotonin was abolished completely, except in the
medial PCA in 1 eye. CONCLUSIONS: Serotonin, in the presence of
atherosclerotic lesions, can cause transient, complete occlusion or
impaired blood flow in the central retinal artery and/or PCA. We speculate
that this mechanism may play a role in the development of ischemic
disorders of the retina and optic nerve head. Discontinuing the atherogenic
diet abolished or markedly improved the serotonin-induced vasoconstriction
within a few months.
