Document Detail

Effects of clonidine on cerebral blood flow and the response to arterial CO2.
MedLine Citation:
PMID:  3011828     Owner:  NLM     Status:  MEDLINE    
CBF, as measured by the clearance of 133Xe or 85Kr in the pentobarbital-anesthetized cat, displays a monotonic increase as the PaCO2 is elevated over a range of 20-60 mm Hg (slope Xe, 1.65 +/- 0.14 ml/100g/min/mm Hg; slope Kr, 1.40 +/- 0.11 ml/100 g/min/mm Hg). Clonidine (20 micrograms/kg i.v.), a centrally acting, alpha 2-preferring agonist, reduced the slope of the PaCO2-CBF response functions for Xe and Kr by 70 and 64%, respectively. Clonidine reduced normocarbic CBF-Xe by 36%, but had no effect on normocarbic CBF-Kr. ST-91, a polar structural analog of clonidine that does not cross the blood-brain barrier, did not reproduce the effects of clonidine when administered at an equivalent dose. This indicates that the effects of clonidine observed were secondary to its action on central rather than peripheral sites. In addition to the effects on the clearance of CBF markers, clonidine reduced the increased MABP otherwise evoked by elevated PaCO2. Reduction in the MABP response to PaCO2 did not account for the lowering of CBF during hypercarbia. In separate experiments where MABP was elevated to correspond with the PaCO2-MABP response observed in the absence of clonidine, a comparable reduction in the slope of the PaCO2 response was also observed. In addition, the pressure autoregulatory response was unaltered after clonidine treatment. These observations suggest that the central action of alpha 2-receptors on the CBF-CO2 response cannot be attributed to an altered perfusion pressure.
I S Kanawati; T L Yaksh; R E Anderson; R W Marsh
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism     Volume:  6     ISSN:  0271-678X     ISO Abbreviation:  J. Cereb. Blood Flow Metab.     Publication Date:  1986 Jun 
Date Detail:
Created Date:  1986-07-07     Completed Date:  1986-07-07     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8112566     Medline TA:  J Cereb Blood Flow Metab     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  358-65     Citation Subset:  IM    
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MeSH Terms
Blood Pressure / drug effects
Carbon Dioxide / blood*
Cerebrovascular Circulation / drug effects*
Clonidine / pharmacology*
Pia Mater / blood supply
Receptors, Adrenergic, alpha / physiology
Xenon Radioisotopes
Grant Support
Reg. No./Substance:
0/Radioisotopes; 0/Receptors, Adrenergic, alpha; 0/Xenon Radioisotopes; 124-38-9/Carbon Dioxide; 4205-90-7/Clonidine; 7439-90-9/Krypton

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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