The toxin helothermine affects potassium currents in newborn rat cerebellar granule cells |
| |
Authors: | M Nobile V Magnelli L Lagostena J Mochca-Morales L D Possani G Prestipino |
| |
Institution: | (1) Istituto di Cibernetica e Biofisica, CNR, Via Dodecanese 33, 16146 Genova, Italy;(2) Dip. Anatomia e Fisiologia Umana, Universitá di Torino, 10125 Torino, Italy;(3) Instituto de Biotecnologia, UNAM, 62271 Cuernavaca, Mexico |
| |
Abstract: | Helothermine, a recently isolated toxin from the venom of the Mexican beaded lizard Heloderma horridum horridum was tested on K+ currents of newborn rat cerebellar granule cells. In whole-cell voltageclamp experiments, cerebellar granule neurons exhibited at least two different K+ current components: a first transient component which is similar to an I
A-type current, is characterized by fast activating and inactivating kinetics and blocked by 4-aminopyridine; a second component which is characterized by noninactivating kinetics, is blocked by tetraetylammonium ions and resembles the classical delayed-rectifier current. When added to the standard external solution at concentrations ranging between 0.1 and 2 m helothermine reduced the pharmacologically isolated I
A-type current component in a voltage- and dose-dependent way, with a half-maximal inhibitory concentration (IC50) of 0.52 m. A comparison between control and nelothermine-modified peak transient currents shows a slowdown of activation and inactivation kinetics. The delayed-rectifier component inhibition was concentration dependent (IC50 = 0.86 m) but not voltage dependent. No frequency-or use-dependent block was observed on both K+ current types. Perfusing the cells with control solution resulted in quite a complete current recovery. We conclude that helothermine acts with different affinities on two types of K+ current present in central nervous system neurons. |
| |
Keywords: | Cerebellar granule neuron Heloderma horridum Helothermine Potassium current Patch clamp |
本文献已被 SpringerLink 等数据库收录! |
|