Fig. 2.

Example of effects of surface temperature on ongoing synaptic activity. A: 2-photon maximum intensity fluorescence side-projection of a layer 2/3 pyramidal neuron in barrel cortex during somatic whole-cell recording. The neuron was filled with indicator (Alexa 594) through the recording pipette, which is visible to the right of the image. The pial surface of the cortex is visible as punctate staining near the top of the image. B: surface temperature (temp.) and intracellular membrane potential (Vm.) of the neuron in A. The brain surface was warmed by perfusion with ACSF at 38°C. The brain surface was initially at ∼28°C with no perfusion. The perfusion began after almost 10 min of recording. After the surface temperature warmed to ∼36°C, the heater was switched off, and the brain surface cooled once more to ∼29°C. Heating the perfusate a 2nd time had a similar effect. The membrane potential of the neuron was recorded throughout these manipulations. C: membrane potential recordings from 5 periods at ∼28°C (blue) and ∼36°C (red) at the times indicated in B. Dashed horizontal lines mark −70 mV. D: membrane potential frequency histograms for the traces in C.