Brain microvessel receptor function during aging.
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Biomedical subjects
Publications and source records attributed to M S Magnoni.
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The effect of chronic ethanol consumption on the binding (125I)-iodohydroxybenzylpindolol to beta-adrenergic receptors in rat brain microvessels has been studied. The results show that chronic ethanol treatment increases the number of beta-receptors present in brain microvessels without changing the binding affinity of the binding site for the beta-adrenoceptor ligand. This effect is apparently not associated with changes in peripheral adrenergic tone, since no differences in platelet epinephrine or norepinephrine concentrations were found between ethanol-treated and control animals. An increase in beta-receptor density in brain microvessels might contribute to the alterations of cerebral blood flow and oxygen consumption reported during chronic ethanol intoxication.
Beta-adrenergic receptor function was measured in cerebral microvessels of spontaneously and DOCA-salt hypertensive rats using 125I-iodohydroxybenzylpindolol (IHYP). Both in genetic and in experimental hypertension, a significant decrease in the number of beta-receptor sites was observed, without receptor affinity changes. These results suggest that alterations of central adrenergic regulation of small vessels may participate in the pathogenetic mechanisms leading to the development of the central hypertensive disease.
beta-adrenergic receptors were measured in cerebral microvessels of gerbils and rats after ligature of the right or left common carotid artery. The results indicate a decrease in the number of beta-adrenergic receptors in brain microvessels of both ipsilateral and contralateral hemispheres. This event may reflect altered patterns of the neuronal regulation of brain microvasculature and may be related to cerebrovascular alterations which are concomitant with ischemia. Furthermore, the results show that the decrease in beta-receptor density is more pronounced in the left hemisphere, independently on the side of carotid occlusion. This finding suggests that microvessel function in the left side of the brain is more vulnerable to hypoxia effects.
The effect of short term and long term ischemia induced by right carotid occlusion was studied on beta-adrenergic receptor function in rat cerebral microvessels. The results show a different time-dependent responsiveness of the two hemispheres to ischemia, with a pronounced and more persistent decrease in the number of capillary beta-receptors in the left side of the brain. The data suggest the existence of asymmetries in the control of brain microvasculature which may mediate the different time-course of beta-receptor changes in response to ischemia.
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Ethanol alters equilibrium between neurotransmitter availability, receptor systems and biological responsiveness. This action may contribute to the accelerating effects of ethanol on the aging process. On this line, the interaction between age and ethanol consumption was studied at laboratory and clinical levels.