A quantitative morphological analysis of the perivascular nerve terminals of cerebral arteries during moderate hypoglycemia was performed. 5-Hydroxydopamine (5-OHDA) was applied to discriminate dense-cored vesicles, related to noradrenaline, and clear vesicles, related to acetylcholine, under the electron microscope. Five hypoglycemic and 5 normoglycemic cats, all receiving 5-OHDA, were compared. In both the middle cerebral artery and vertebral artery, the dense-cored vesicles were significantly smaller and clear vesicles were significantly larger in hypoglycemia than in normoglycemia. These morphological changes in the vesicles may indicate hyperactivity of the sympathetic system and hypoactivity of the parasympathetic system of the cerebral vessels during hypoglycemia.
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