title: Entry of opioid peptides into the central nervous system.
abstract: Cerebrovascular permeability of four modified opioid peptides--[D-Ala2]methionine enkephalin amide, beta-[D-Ala62,14C-Homoarg69]lipotropin 61 -69, alpha-[D-Ala2,14C-Homoarg9]endorphin, and beta-[D-Ala2,14C-Homoarg]endorphin--ranged from 1.4 to 3.9 X 10(-6) centimeters per second in brain regions of the conscous rat. These significant permeabilities should allow the peptides to fill the extracellular brain space with a half time of 3 to 11 minutes, as a result of a step increase in plasma concentration of unbound peptide.
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D002199:Capillary Permeability; D004723:Endorphins / Q000378:metabolism*; D004745:Enkephalins / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D008297:Male; D051381:Rats; D012995:Solubility; D008083:beta-Lipotropin / Q000378:metabolism*
chemical_list: D004723:Endorphins; D004745:Enkephalins; D008083:beta-Lipotropin