Author(s): Baba M, Oishi R, Saeki K
Abstract Share this page
Abstract The effects of opioids on the permeability of the blood-brain barrier (BBB) were examined in mice with sodium fluorescein as an indicator of the permeability. The brain was perfused with saline 30 min after injection of sodium fluorescein (40 mg/kg, i.v.) and examined by fluorometry. Morphine hydrochloride (0.3-10 mg/kg, s.c.) markedly increased the brain level of sodium fluorescein dose-dependently without influencing the plasma level, when administered 20 min before sodium fluorescein injection. Intracerebroventricularly (i.c.v.) injected morphine hydrochloride (0.5 and 1.0 microgram) increased the brain sodium fluorescein level. Buprenorphine (0.1 and 0.5 mg/kg, s.c.) was also effective. However, pentazocine, ethylketazocine, U-50488H and SKF-10047 had no significant influence. The i.c.v. administration of [D-Ala2, MePhe4, Gly(ol)5]enkephalin (0.1 microgram) and [D-Ala2, D-Leu5]enkephalin (0.5 microgram) but not of [D-Thr2, Leu5]enkephalin-Thr increased the brain level of sodium fluorescein significantly. A small dose of naloxone (i.p.) significantly inhibited the effects of morphine, buprenorphine, [D-Ala2, MePhe4, Gly(ol)5]enkephalin and [D-Ala2, D-Leu5]enkephalin. ICI-174864 coadministered i.c.v. with [D-Ala2, D-Leu5]enkephalin was ineffective in antagonizing the effect of the latter. These findings suggest that the stimulation of mu opioid receptors results in an increase in BBB permeability to sodium fluorescein.
This article was published in Naunyn Schmiedebergs Arch Pharmacol
and referenced in Journal of Pulmonary & Respiratory Medicine