Please cite this article in press as: Islas LD, et al. A simple method for fast temperature changes and its application to thermal activation of TRPV1 ion channels. J Neurosci Methods (2015), http://dx.doi.org/10.1016/j.jneumeth.2015.02.003 ARTICLE IN PRESS G Model NSM-7144; No. of Pages 6 Journal of Neuroscience Methods xxx (2015) xxx–xxx Contents lists available at ScienceDirect Journal of Neuroscience Methods jo ur nal ho me p age: www.elsevier.com/locate/jneumeth A simple method for fast temperature changes and its application to thermal activation of TRPV1 ion channels León D. Islas a,∗ , Victor De-la-Rosa a , Beatriz Rodríguez-Cortés a , Gisela E. Rangel-Yescas a , David Elias-Vi ˜ nas b a Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), México City 04510, Mexico b Sección de Bioelectrónica, CINVESTAV-IPN, México City 07360, Mexico h i g h l i g h t s • We present a simple and effective method for rapid changes in the local temperature around a patch-clamped membrane or cell. • The method is based on the resistive heating of a thin copper filament enclosed in a tight-fitting glass capillary. • We have tested its function by recording heat-activated currents in HEK 293 cells expressing TRPV1 heat-sensitive ion channels. a r t i c l e i n f o Article history: Received 19 October 2014 Received in revised form 16 January 2015 Accepted 3 February 2015 Available online xxx Keywords: TRPV1 channel Heat activation ThermoTRPs Resistive heating Patch-clamp Ion channels a b s t r a c t Background: Thermally activated ion channels function as molecular thermometers and participate in other physiological important functions. The mechanism by which they acquire their exquisite temper- ature sensitivity is unknown and is currently an area of intense research. For this reason, there is a need for diverse methods to deliver controlled temperature stimuli. New method: We have developed a simple, inexpensive and reliable method to deliver temperature pulses to small volumes surrounding the recording area, which can be either a patch-clamp pipette containing a cell-free membrane with thermally activated channels or a whole cell attached to a pipette. Results: Here we developed a micro-heater based on resistive heating of a copper filament enclosed in a glass capillary that is capable of delivering fast and localized temperature changes. We validated the performance of the micro-heaters by analyzing the heat-induced activation of TRPV1 thermoTRP channels recorded in inside-out patches and demonstrate the use of the micro-heaters. Comparison with existing method(s): The micro-heaters we introduce here are compact, easy to fabricate and to operate. In contrast with bulk solution heaters commercially available, our method is extremely affordable and simple to operate. To the best of our knowledge there are no other similar, commercially available heating methods. Conclusions: The micro-heater method is simple and should provide a straightforward and rapid experi- mental tool to study mechanisms in thermally activated ion channels. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Thermally activated ion channels are an important family of membrane proteins associated with sensory perception of temperature and nociceptive processes (Caterina et al., 1997; Everaerts et al., 2011). While some of these channels are activated ∗ Corresponding author. Tel.: +52 5556232132. E-mail addresses: leon.islas@gmail.com, lislas@canales.facmed.unam.mx (L.D. Islas). by decreases in temperature (Peier et al., 2002; Brauchi et al., 2004), others open in response to increased temperature. The most important representatives of the later belong to the TRPV subfamily of TRP ion channels, which are found both in vertebrates and invertebrates. The most thoroughly characterized member of this subfamily is the TRPV1 cation-selective ion channel. This channel can be gated by very diverse chemical stimuli, opening in response to binding of capsaicin and the endogenous ligands LPA (Nieto-Posadas et al., 2011) and anandamide (Zygmunt et al., 1999). Perhaps more importantly, TRPV1 is directly activated by increases in temperature in the range of 40 ◦ C to 50 ◦ C (Caterina and http://dx.doi.org/10.1016/j.jneumeth.2015.02.003 0165-0270/© 2015 Elsevier B.V. All rights reserved.