Voltage-induced activation of mechanosensitive cation channels of leech neurons.
The voltage dependence of stretch-activated cation channels in leech central neurons was studied in cell-free configurations of the patch-clamp technique. We established that stretch-activated channels excised from identified cell bodies of desheathed ganglia, as well as from neurons in culture, were slowly and reversibly activated by depolarizing membrane potentials. Negative pressure stimuli, applied to the patch pipette during a slow periodical modulation of membrane potential, enhanced channel activity, whereas positive pressures depressed it. Voltage-induced channel activation was observed, with soft glass pipettes, both in inside-out and outside-out membrane patches, at negative and positive reference potentials, respectively. The results presented in this study demonstrate that membrane depolarization induces slow activation of stretch-activated channels of leech central neurons. This phenomenon is similar to that found in Xenopus oocytes, however, some peculiar features of the voltage dependence in leech stretch-activated channels indicate that specific membrane-glass interactions might not necessarily be involved. Moreover, following depolarization, stretch-activated channels in membrane patches from neurons in culture exhibited significantly shorter delay to activation (sec) than their counterparts from neurons of freshly isolated ganglia (hundreds of sec).
Dipartimento di Fisiologia e Biochimica G. Moruzzi, Università di Pisa, Via S. Zeno 31, 56127, Pisa, Italy.
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D000818:Animals; D002412:Cations; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D004594:Electrophysiology; D007473:Ion Channels / Q000378:metabolism*; D007865:Leeches; D008465:Mechanoreceptors / Q000378:metabolism*; D008564:Membrane Potentials; D009474:Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques
D002412:Cations; D007473:Ion Channels