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This Article Full Text Full Text (PDF) All Versions of this Article: 575/1/175    most recent jphysiol.2006.113308v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wladyka, C. L. Articles by Kunze, D. L. Search for Related Content PubMed PubMed Citation Articles by Wladyka, C. L. Articles by Kunze, D. L. Related Collections Neuroscience

¹ Rammelkamp Centre for Research and Education, MetroHealth Medical Centre and Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44109, USA

The M-current is a slowly activating, non-inactivating potassium current that has been shown to be present in numerous cell types. In this study, KCNQ2, Q3 and Q5, the molecular correlates of M-current in neurons, were identified in the visceral sensory neurons of the nodose ganglia from rats through immunocytochemical studies. All neurons showed expression of each of the three proteins. In voltage clamp studies, the cognition-enhancing drug linopirdine (1–50 µM) and its analogue, XE991 (10 µM), quickly and irreversibly blocked a small, slowly activating current that had kinetic properties similar to KCNQ/M-currents. This current activated between –60 and –55 mV, had a voltage-dependent activation time constant of 208 ± 12 ms at –20 mV, a deactivation time constant of 165 ± 24 ms at –50 mV and V_1/2 of –24 ± 2 mV, values which are consistent with previous reports for endogenous M-currents. In current clamp studies, these drugs also led to a depolarization of the resting membrane potential at values as negative as –60 mV. Flupirtine (10–20 µM), an M-current activator, caused a 3–14 mV leftward shift in the current–voltage relationship and also led to a hyperpolarization of resting membrane potential. These data indicate that the M-current is present in nodose neurons, is activated at resting membrane potential and that it is physiologically important in regulating excitability by maintaining cells at negative voltages.

(Received 10 May 2006; accepted after revision 14 June 2006; first published online 15 June 2006)
Corresponding author D. L. Kunze: Rammelkamp Centre for Research and Education R326 MetroHealth Medical Centre, 2500 MetroHealth Drive, Cleveland, OH 44109-1998, USA.  Email: dkunze{at}metrohealth.org

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