Laser-Doppler assessment of brain microcirculation: effect of local alterations.
The objective of this study was to determine whether changes in blood perfusion measured by laser-Doppler (LD) flowmetry correlate with simultaneously measured changes in pial arteriolar diameter after local application of vasoactive agents on the brain surface. A closed cranial window was implanted in anesthetized rabbits. A 0.84-mm-diam LD probe was inserted through one window port and fixed at a distance of 1-2 mm from the cortical surface. The probe detects changes in perfusion within a tissue volume of approximately 1 mm3. The diameter of pial arterioles in the area adjacent to the LD probe was simultaneously measured with a microscope and image-splitting device. Topical application of bradykinin (80 nM to 8 microM), which stimulates the formation of dilator prostaglandins and O2 radicals, induced a dose-dependent arteriolar dilation and increase in LD flow. Topical application of 33 microM 2-chloroadenosine, a stable analogue of adenosine, induced the same degree of pial arteriolar dilation as 8 microM bradykinin but produced a much larger increase in LD flow, probably due to its greater tissue penetration and stability. At 5 min after bradykinin washout the arterioles had nearly returned to their control diameter, whereas LD flow was still increased. Similarly, there was a discrepancy between LD flow and diameter changes after washout of 2-chloroadenosine. We conclude that LD flowmetry is a useful technique for continuous assessment of cortical blood flow in response to topically applied agents.(ABSTRACT TRUNCATED AT 250 WORDS)
Haberl
R L
RL
Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
Heizer
M L
ML
Ellis
E F
EF
D015762:2-Chloroadenosine; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D001921:Brain / Q000098:blood supply*; D002536:Cerebral Arteries / Q000187:drug effects; D002560:Cerebrovascular Circulation; D007834:Lasers; D008297:Male; D008833:Microcirculation / Q000502:physiology; D011817:Rabbits; D012039:Regional Blood Flow; D014664:Vasodilation / Q000187:drug effects
D015762:2-Chloroadenosine; D000241:Adenosine; D001920:Bradykinin