Ultrastructural and Histochemical Studies of Cerebral Capillary Synapses
Evidence for a central adrenergic pathway originating in the brain stem and innervating intracerebral vessels has been presented in the preceding chapters by Hartman and Preskorn and their colleagues. They concluded that this system regulates the permeability of and the flow through cerebral microvessels. The anatomic evidence supporting this hypothesis consists of axonal varicosities surrounded by the basal lamina of endothelial cells in cat hypothalamus (1) and varicosities directly in contact with the basal lamina of capillaries in the paraventricular nucleus of rat (2). This close anatomic relationship between axonal varicosities and capillaries has not been described in other regions of the brain and generalizations based upon relationships found in the hypothalamus may be invalid because relationships in the hypothalamus between neurons and capillaries may not be typical of the rest of the brain. The hypothesis then relies heavily on physiologic and pharmacologic evidence due to this relative lack of specific anatomic data.
KeywordsBasal Lamina Paraventricular Nucleus Amyl Acetate Cerebral Microvessels Electron Dense Body
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