Epinephrine increases the selective permeability of epidurally administered [3H]-D-mannitol and [14C]-carboxyl-inulin across the blood-spinal cord barrier.
A rabbit experimental model was used to ascertain how epinephrine influences uptake of epidurally-administered [3H]-D-mannitol and [14C]-carboxyl-inulin into regions of brain and spinal cord. [3H]-D-mannitol and [14C]-carboxyl-inulin, 20 microCi each, were distributed in normal saline (control) and normal saline with 0.03 microM (1:200,000 diluted) epinephrine. These tracers were administered as bolus and slow epidural infusion for 90 min. Epinephrine decreased the uptake of [3H]-D-mannitol and [14C]-carboxyl-inulin into the serum collected at 15, 30, 45, 60, 75 and 90 min intervals during the administration of tracers. Epinephrine did not alter the uptake of [3H]-D-mannitol and [14C]-carboxyl-inulin into the regions of the brain (cerebrum, cerebellum, brain stem including midbrain and pons) and upper regions of the spinal cord (mid-cervical and mid-thoracic) compared to controls. The uptake of [3H]-D-mannitol and [14C]-carboxyl-inulin into the mid-lumbar region is significantly increased compared to the control. The differential uptake of [3H]-D-mannitol and [14C]-carboxyl-inulin into 1 cm thick sections of lumbo-sacral cord was significantly increased by epinephrine at the site of the epidural catheter placement, while sections of the cord distal on either end (thoracic and sacral ends) did not show significant differences compared to the control. The efficacy of epinephrine in increasing spinal cord uptake of hydrophilic [3H]-D-mannitol and [14C]-carboxyl-inulin may be attributed to its vasoconstrictive properties and its ability to increase vascular endothelial cell permeability across the blood-spinal cord barrier.
Naidu
K A
KA
Department of Neurology, College of Medicine, University of South Florida, Tampa 33612, USA.
Fu
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ES
Prockop
L D
LD
D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects*; D001921:Brain / Q000378:metabolism; D002199:Capillary Permeability / Q000187:drug effects*; D002245:Carbon Dioxide / Q000493:pharmacokinetics*; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics; D004730:Endothelium, Vascular / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology*; D007268:Injections, Epidural; D007444:Inulin / Q000493:pharmacokinetics*; D008297:Male; D008353:Mannitol / Q000493:pharmacokinetics*; D011817:Rabbits; D013116:Spinal Cord / Q000098:blood supply* / Q000378:metabolism
D002250:Carbon Radioisotopes; D002245:Carbon Dioxide; C041069:carboxyl radical; D008353:Mannitol; D007444:Inulin; D004837:Epinephrine