R-PHENYLISOPROPYL-ADENOSINE INCREASES SPINAL-CORD BLOOD-FLOW AFTER INTRATHECAL INJECTION IN THE RAT

The A1-adenosine receptor agonist, R-phenylisopropyl-adenosine (R-PIA) , demonstrated antinociceptive properties in animal studies after intr athecal administration. In the evaluation of a drug for possible spina l injection in humans, the effects of intrathecal R-PIA on spinal cord blood flow (SCBF) were investigated using the laser-Doppler flowmetry technique in anesthetized rats. In low doses (0.1-1 nmol), no change in SCBF was recorded, whereas larger doses (10-100 nmol) caused a sign ificant increase in SCBF. No change in systemic arterial blood pressur e could be seen, except for a decrease after administration of the lar gest dose of R-PIA (100 nmol). It is concluded that R-PIA in doses of 10 nmol and larger induces an increase in SCBF after intrathecal injec tion in anesthetized rats and that an increase in blood flow is seen b efore any effect on the systemic circulation is detected. It can also be deduced that the antinociceptive effects of R-PIA after intrathecal injection are not a consequence of spinal ischemia and that disturban ces in local blood flow cannot be expected to constitute a neurotoxic factor.