Influence of electrical stimulation of locus coeruleus on the rat blood-brain barrier permeability to sodium fluorescein.
The role of central adrenergic innervation of the brain capillaries is still a matter of discussion. The hypothesis that these nerves control the blood-brain barrier permeability was tested by electrically stimulating the locus coeruleus, the major central adrenergic nucleus, in the anaesthetized rat. Frequencies of 5, 15, and 30 Hz were used. A frequency dependent increase in blood-brain barrier permeability to sodium fluorescein was verified. Prior administration of the alpha-adrenoceptor antagonist phenoxybenzamine (10 mg/kg i.p., 24 h before electrical stimulation) totally blocked the effect of 15 Hz stimulation. The same dose of pindolol (a beta-adrenoceptor antagonist) given 1 h before electrical stimulation potentiated the effect of 5 Hz stimulation. Thus, blood-brain barrier permeability is increased, in a frequency dependent manner, by electrical stimulation of the locus coeruleus. The results obtained with phenoxybenzamine and pindolol suggest an opposite effect of alpha and beta-adrenoceptors on the control of sodium fluorescein transport through the blood-brain barrier.
Sarmento
A
A
Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal.
Borges
N
N
Lima
D
D
D000320:Adrenergic Fibers / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000098:blood supply; D002196:Capillaries / Q000294:innervation; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D004558:Electric Stimulation; D019793:Fluorescein; D005452:Fluoresceins / Q000493:pharmacokinetics*; D006863:Hydrogen-Ion Concentration; D008125:Locus Coeruleus / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000097:blood; D010643:Phenoxybenzamine / Q000494:pharmacology; D010869:Pindolol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D005452:Fluoresceins; D010643:Phenoxybenzamine; D002245:Carbon Dioxide; D010869:Pindolol; D010100:Oxygen; D019793:Fluorescein