Document Detail

Alpha-1 adrenergic receptor control of the cerebral vasculature in humans at rest and during exercise.
MedLine Citation:
PMID:  23024369     Owner:  NLM     Status:  Publisher    
Abstract: We tested the hypothesis that pharmacologic blockade of α-1 adrenoreceptor (prazosin), at rest and during steady-state dynamic exercise would impair cerebral autoregulation (CA) and result in cerebral vasodilatation in healthy humans. In ten subjects beat-to-beat mean arterial pressure (MAP) and mean middle cerebral artery blood velocity (MCA V) were determined at rest, and during low (Ex90) and moderate workload (Ex130) on an upright bicycle ergometer without and with prazosin. Plasma noradrenaline concentrations increased significantly from rest to Ex130 during control (from 1.8±0.2 to 3.2±0.3 pmol/ml plasma). In the control condition the transfer function gain between MAP and MCA V in the low frequency (LF) range was decreased at Ex90 (P = 0.035) and Ex130 (P = 0.027) from rest. A significant increase in critical closing pressure (CCP) was also observed in the control condition from rest to Ex90 to Ex130 (from 18±3 to 24±4 to 31±4 mm Hg). An average of 74±2% blockade of blood pressure response was achieved with oral prazosin. Following blockade, plasma noradrenaline concentrations further increased at rest and Ex130 from the control (from 2.6±0.3 to 4.4±0.5 pmol/ml plasma). Prazosin also resulted in an increase in LF gain (P < 0.003) compared to the control condition. Prazosin blockade abolished the increases in CCP during Ex130 and increased the cerebrovascular conductance index (P = 0.018). These data indicate that in the control condition a strengthening of CA occurred with moderate dynamic exercise that is associated with an increase in CCP as a result of the exercise mediated augmentation of sympathetic activity. As α-1 adrenergic receptor blockade attenuated the increase in dynamic CA and CCP, we conclude that increases in sympathetic activity have a role in establishing cerebral vascular tone in humans.
Sushmita Purkayastha; Ashwini Saxena; Wendy L Eubank; Besim Hoxha; Peter B Raven
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-9-28
Journal Detail:
Title:  Experimental physiology     Volume:  -     ISSN:  1469-445X     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-10-1     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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