Comparative Effects of Heterologous TRPV1 and TRPM8 Expression in Rat Hippocampal Neurons
Figure 7
Agonist treatment in 0.5 µM tetrodotoxin (TTX) increases presynaptic transmitter release in transfected neurons.
(A) Fluorescence image of a TRPM8-transfected neuron (green) forming presumed presynaptic contacts onto a postsynaptically-recorded cell (red) filled with Alexa Fluor 568, which was included in the recording pipette. Scale bar denotes 50 µM. (B) Example of miniature excitatory postsynaptic currents (mEPSCs) recorded from non-transfected postsynaptic partners of TRPM8-transfected neurons (bottom panel) or from non-transfected neurons not in contact with transfected neurons (top panel) in 0.5 µM TTX. During 100 µM menthol application, mEPSC and mIPSC frequency increased in neurons postsynaptic to TRPM8-transfected neurons but not in control neurons. (C) Quantification of the mPSC frequency during 100 µM menthol application compared to the baseline frequency (dashed line). Error bars represent SEM. In neurons postsynaptic to TRPM8-transfected neurons, but not in control neurons, the mPSC frequency increased significantly in menthol (Fisher's exact test, p<0.005). (D) Quantification of the mPSC frequency during 500 nM capsaicin application compared to baseline frequency (dashed line) in neurons postsynaptic to TRPV1-transfected neurons or to control neurons. Error bars represent SEM. In neurons postsynaptic to TRPV1-transfected neurons, but not to non-transfected neurons, the mPSC frequency in capsaicin increased significantly (Fisher's exact test, p<0.01).
