The effects of subarachnoid space injection of somatostatin on the spinal cord blood flow in the rat: A comparison of administration techniques

The subarachnoid injection of the peptide somatostatin (SOM) in the lumbar spinal cords of rats produced reductions in spinal cord blood flows that varied greatly, depending upon the injection technique. Neurologically impairing doses of SOM (6.2, 12.5 nmol) were injected through an indwelling intrathecal catheter (i.t.) or intervertebral needle (v.n.), and cardiac output, brain and spinal cord blood flows were measured using radiolabeled microspheres. Both doses of SOM caused considerable reductions in lumbosacral cord perfusion 5 min following each injection; blood flow recovered to pre-treatment baseline levels by 10 and 30 min after i.t. injection, at 6.2 and 12.5 nmoles of SOM, respectively. In contrast, lumbosacral blood flows remained significantly reduced 30 min following v.n. injections, and greater reductions were measured in cardiac output, brain, cervical and thoracic cord blood flows. These results reveal that SOM has dose-dependent vasoconstrictory effects in the rat spinal cord, and that the effects of subarachnoid injection of SOM on spinal cord perfusion and related neuronal damage are clearly dependent upon the injection technique.