Effects of clonidine on cerebral blood flow and the response to arterial CO2

Journal Article · Sun Jun 01 04:00:00 EDT 1986 · J. Cereb. Blood Flow Metab.; (United States)

DOI:https://doi.org/10.1038/jcbfm.1986.60· OSTI ID:5231459

Kanawati, I S; Yaksh, T L; Anderson, R E; Marsh, R W

CBF, as measured by the clearance of /sup 133/Xe or /sup 85/Kr in the pentobarbital-anesthetized cat, displays a monotonic increase as the PaCO/sub 2/ 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 PaCO/sub 2/-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 PaCO/sub 2/. Reduction in the MABP response to PaCO/sub 2/ did not account for the lowering of CBF during hypercarbia. In separate experiments where MABP was elevated to correspond with the PaCO/sub 2/-MABP response observed in the absence of clonidine, a comparable reduction in the slope of the PaCO/sub 2/ 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-CO/sub 2/ response cannot be attributed to an altered perfusion pressure.

• Research Organization: Mayo Clinic, Rochester, MN
• OSTI ID: 5231459
• Journal Information: J. Cereb. Blood Flow Metab.; (United States), Journal Name: J. Cereb. Blood Flow Metab.; (United States) Vol. 3; ISSN JCBMD
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
ARTERIES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BLOOD FLOW
BLOOD PRESSURE
BLOOD VESSELS
BLOOD-PLASMA CLEARANCE
BODY
BRAIN
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARDIOVASCULAR SYSTEM
CATS
CENTRAL NERVOUS SYSTEM
CEREBRUM
CHALCOGENIDES
CLEARANCE
DAYS LIVING RADIOISOTOPES
DRUGS
EVEN-ODD NUCLEI
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
KRYPTON 85
KRYPTON ISOTOPES
MAMMALS
NERVOUS SYSTEM
NUCLEI
ORGANS
OXIDES
OXYGEN COMPOUNDS
RADIOISOTOPES
TRACER TECHNIQUES
VERTEBRATES
XENON 133
XENON ISOTOPES
YEARS LIVING RADIOISOTOPES