The presence in pig brain of an endogenous equivalent of apamin, the bee venom peptide that specifically blocks Ca2+-dependent K+ channels.
An apamin-like factor has been isolated from pig brain after extraction of the tissue and purification on sulfopropyl-Sephadex C-25 and on reversed-phase high pressure liquid chromatography. The apamin-like factor has the following properties: (i) it prevents 125I-labeled apamin binding to its specific receptor site present on rat brain synaptosomes, (ii) it is active in the radioimmunoassay for apamin (i.e., it prevents 125I-labeled apamin precipitation by anti-apamin antibodies), (iii) it induces contraction of guinea pig intestinal smooth muscle previously relaxed with epinephrine, and (iv) it blocks Ca2+-dependent K+ channels responsible for the long-lasting afterpotential hyperpolarization following the action potential in rat skeletal muscle cells in culture. All these properties are those of apamin itself. The apamin-like factor is a peptide that, like apamin, is destroyed by trypsin and unaffected by chymotrypsin. These results suggest the presence in mammalian brain of a potent Ca2+-dependent K+-channel modulator.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001030:Apamin; D001514:Bee Venoms; D001923:Brain Chemistry; D007473:Ion Channels / Q000187:drug effects; D009132:Muscles / Q000187:drug effects; D009419:Nerve Tissue Proteins / Q000302:isolation & purification*; D010447:Peptide Hydrolases; D013552:Swine
D001514:Bee Venoms; D007473:Ion Channels; D009419:Nerve Tissue Proteins; D001030:Apamin; D010447:Peptide Hydrolases