Figure 2

Thermostimulation setup.

(a) Top panel: Implementation of the thermal stimulation device for the plantar hindpaw within the ROCKET mouse holder system. Bottom panel: Functional scheme of the thermal stimulation system: the Peltier element (PE) is attached to a heat sink cooled by water circulation. The PE’s driving current is feedback controlled and monitored by a thermoprobe within a copper plate (the thermode) covering the entire PE surface. The paw is positioned between the thermode and an inflatable balloon connected to a water-filled cylinder, whose filling level determines the contact pressure. (b) Top panel: To test for B₀-effects induced by the stimulation system a 2% agarose phantom was positioned below the CryoProbe. Bottom panel: Coronal views of field changes measured in an agarose phantom induced by the current in the Peltier element. Top: Field change induced by baseline heating current; center: Field change induced by maximum heating current; bottom: Expected signal change in percent due to field change induced by switching from baseline heating to maximum heating. The contours indicate the position of the mouse brain during fMRI. (c) Stimulation temperature plot during a defined heat paradigm (35.5 °C baseline, 48 °C stimulus, 4 °C/s, 20 s). Measuring locations are illustrated in the above scheme: the PE control temperature measured within the thermode core (TC), on the thermode surface (TS) and at the thermode-skin-interface (TSI). Dashed lines indicate the delays until TSI temperature reaches 42 °C (TRPV1 activation threshold) and 46 °C (stimulation target temperature). (d) Infrared image of a hindpaw from an awake mouse indicating its adaptation to the respective thermal ambient. Measured at room temperature (20 °C).