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Helothermine, a lizard venom toxin, inhibits calcium current in cerebellar granules.
Nobile, M; Noceti, F; Prestipino, G; Possani, L D.
Afiliación
  • Nobile M; Istituto di Cibernetica e Biofisica, CNR, Genova, Italy.
Exp Brain Res ; 110(1): 15-20, 1996 Jun.
Article en En | MEDLINE | ID: mdl-8817251
Helothermine (HLTx), a 25.5-kDa peptide toxin isolated from the venom of the Mexican beaded lizard (Heloderma horridum horridum), was found to be an inhibitor of Ca2+ channels in cerebellar granule cells of newborn rats. Macroscopic currents, carried by 10 mM Ba2+, were measured in whole-cell configuration. The toxin at the saturating dose of 2.5 microM reversibly produced an approximately 67% block of the voltage-dependent Ca2+ current by a fast mechanism of action. The current inhibition and recovery were reached in less than 1 min. Inhibition was concentration-dependent, with a half-effective dose of 0.25 microM. The current block was practically voltage-independent, whereas the steady-state inactivation h infinity was significantly affected by HLTx (approximately 10 mV). The toxin did not affect the activation and inactivation kinetics of the Ca2+ current. Experiments with other Ca2+ channel blockers showed that HLTx abolished omega-cono-toxin GVIA-sensitive Ca2+ currents, as well as omega-Aga-IVA- and dihydropyridine-sensitive Ca2+ currents. These drugs had virtually no effect when HLTx was applied first. The present results indicate that HLTx produce a high-potency blockage of the three pharmacologically distinct Ca2+ current components.
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Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Péptidos / Ponzoñas / Bloqueadores de los Canales de Calcio / Cerebelo / Lagartos / Neurotoxinas Límite: Animals Idioma: En Revista: Exp Brain Res Año: 1996 Tipo del documento: Article País de afiliación: Italia Pais de publicación: Alemania
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Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Péptidos / Ponzoñas / Bloqueadores de los Canales de Calcio / Cerebelo / Lagartos / Neurotoxinas Límite: Animals Idioma: En Revista: Exp Brain Res Año: 1996 Tipo del documento: Article País de afiliación: Italia Pais de publicación: Alemania