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Updated: Jul 3, 2026

An In Vivo Blood-brain Barrier Permeability Assay in Mice Using Fluorescently Labeled Tracers
Published on: February 26, 2018
Low permeability of the blood-brain barrier to nanomolar concentrations of immunoreactive alpha-melanotropin
1Department of Pharmacology and Therapeutics, University of Wales College of Medicine, Cardiff, UK.
The permeability of the blood-brain barrier (BBB) to immunoreactive alpha-melanotropin (alpha-MSH) was quantified in rats pretreated with monosodium L-glutamic acid to deplete their CNS stores of endogenous alpha-MSH. The methodology, suitable for poorly permeable substances, monitored blood and brain tissue concentrations of alpha-MSH over 15 min following intravenous injection of 30 nmol synthetic alpha-MSH. Rate constants for entry of alpha-MSH into brain tissue were estimated from separate non-linear least-squares fits of connecting two- and one-compartment open models to plasma and extravascular brain tissue concentration data, respectively. Comparisons were made to rate constants measured similarly for 14C-inulin. The BBB had a low permeability to immunoreactive alpha-MSH, consistent with peptide penetrating the barrier by passive diffusion dependent upon the lipid solubility of the molecule.
The permeability of the blood-brain barrier (BBB) to immunoreactive alpha-melanotropin (alpha-MSH) was quantified in rats pretreated with monosodium L-glutamic acid to deplete their CNS stores of endogenous alpha-MSH. The methodology, suitable for poorly permeable substances, monitored blood and brain tissue concentrations of alpha-MSH over 15 min following intravenous injection of 30 nmol synthetic alpha-MSH. Rate constants for entry of alpha-MSH into brain tissue were estimated from separate non-linear least-squares fits of connecting two- and one-compartment open models to plasma and extravascular brain tissue concentration data, respectively. Comparisons were made to rate constants measured similarly for 14C-inulin. The BBB had a low permeability to immunoreactive alpha-MSH, consistent with peptide penetrating the barrier by passive diffusion dependent upon the lipid solubility of the molecule.
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