Article
Inhibition of the intrinsic component of the sympathetic nervous system impaires cerebral autoregulation in a rat AVM model
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Published: | September 16, 2010 |
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Objective: To test the hypothesis that the maintenance of the cerebral autoregulation does not depend on the activity of the sympathetic nervous system (SNS).
Methods: 12 weeks after creation of an extracranial AV-Fistula (Morgan-Type in male Sprague-Dawley rats) (n=40) or sham operation (n=40) rSO2 (spectrophotometry), rCBF (LDF) and MAP were measured continuously. Norepinephrine was administered systemically for static testing of autoregulation before and after fistula occlusion. N=10 fistula or sham animals each underwent 1. no SNS manipulation, 2. extrinsic SNS inhibition via bilateral sympathectomy, 3. intrinsic SNS inhibition via the neurotoxin DSP-4 or 4. complete SNS inhibition. Generalized estimation equations (GEE) were used to estimate the dependency of MAP, rCBF and rSO2.
Results: Within the sham group a maintained cerebral autoregulation could be tested for all animals. Within the fistula rats, a dependency between rCBF/rSO2 and MAP was proven (P<0.001) for animals after inhibition of the intrinsic and complete cerebral noradrenergic system before occlusion of the fistula. After occlusion of the fistula, an impaired cerebral autoregulation could only be tested for DSP-4 treated rats.
Conclusions: For the first time, an impaired cerebral autoregulation under conditions of an altered SNS could be tested in vivo in a rat AVM model. Autoregulation trials suggest the predominant role of the intrinsic noradrenergic system as with inhibition of the extrinsic component of the SNS does not affect cerebral autoregulation.