Effects of adenosine on ocular blood flow.
OBJECTIVE
To determine the effect of intravascular adenosine on blood flow in the ocular fundus and to examine indirectly whether the blood-brain barrier to adenosine, which exists in the cerebrovasculature of the cat, is present in the eye of this animal.


METHODS
The noninvasive techniques of laser Doppler flowmetry and velocimetry along with fundus photography were used to measure the change in optic nerve head and choroidal and retinal blood flow during intravenous infusions of 0.18 and 0.6 mg/kg per minute of adenosine.


RESULTS
Infusions of adenosine induced significant increases in choroidal blood flow (60% with 0.6 mg/kg per minute) but not in optic nerve head or retinal blood flows.


CONCLUSIONS
The lack of effect of intravenously infused adenosine on the optic nerve and retinal circulations is most likely caused by the tight junctions in the vessels of these vascular beds, which prevent adenosine from reaching its receptors. Perivascular adenosine in the choroid most likely accounts for the increase in blood flow in this tissue.
Portellos
M
M
Scheie Eye Institute, University of Pennsylvania, Philadelphia 19104, USA.
Riva
C E
CE
Cranstoun
S D
SD
Petrig
B L
BL
Brucker
A J
AJ
D000241:Adenosine / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D001813:Blood-Retinal Barrier / Q000187:drug effects / Q000502:physiology; D002415:Cats; D002829:Choroid / Q000098:blood supply* / Q000187:drug effects; D005654:Fundus Oculi; D006439:Hemodynamics / Q000502:physiology; D007262:Infusions, Intravenous; D017078:Laser-Doppler Flowmetry; D009898:Optic Disk / Q000098:blood supply* / Q000187:drug effects; D012171:Retinal Vessels / Q000187:drug effects / Q000502:physiology*
D000241:Adenosine