Fig. 8.

SOM-Cre; Ai32 cells are distinguished from non-SOM+ cells by their light-evoked responses at holding membrane potentials toward −50 mV to −60 mV, using the cesium-containing internal solution. A: non-SOM+ cell. Example of ChR2-photoactivated current responses measured by whole cell voltage clamp at different holding membrane potentials is shown. The recoded cell (indicated by the circle) is located in the oval BNST and photoactivated at a perisomatic site (label, 1). Note the absence of downward deflecting currents at −40 and −50 mV. B: SOM+ cell. Example of ChR2-photoactivated current responses measured by whole cell voltage clamp at different holding membrane potentials is shown. The recoded cell is located in the oval BNST, and photoactivated at a perisomatic site (label, 1). Note the presence of downward deflecting currents at −40, −50 and −60 mV, which were caused by direct activation of ChR2-gated cation currents. In comparison, both cells showed strong upward deflecting currents (IPSCs) beyond −20 mV, which resulted from presynaptic SOM-Cre; Ai32 neuronal spiking.