Comparative Effects of Heterologous TRPV1 and TRPM8 Expression in Rat Hippocampal Neurons
Figure 4
Agonist-induced currents in both TRPV1- and TRPM8-transfected neurons are decreased after prolonged exposure.
(A) Examples of TRPV1-transfected neurons exposed to bath application of 500 nM capsaicin, 25 µM D-APV, and 1 µM NBQX acutely (top panel) or for 4 hr (bottom panel) prior to recording in whole-cell voltage clamp. Capsaicin was retained in the bath recording solution. After the whole-cell recording was established, capsaicin was briefly removed by perfusing fresh recording saline for 10 s before 5 s application of 30 mM KCl. (B) Examples of TRPM8-transfected neurons exposed to bath application of 100 µM menthol, 25 µM D-APV, and 1 µM NBQX acutely (top panel) or for 4 hr (bottom panel) prior to recording in whole-cell voltage clamp. Similar to (A), menthol was added to the bath recording solution. Menthol was removed by perfusing fresh, menthol-free recording saline for 10 s before 5 s application of 30 mM KCl. (C) The average ratio of capsaicin current amplitude to KCl current amplitude was calculated for acute and 4 hr applications of capsaicin. Error bars represent SEM. The ratio of capsaicin to KCl current is significantly decreased after 4 hr capsaicin exposure (Student's unpaired t test, p<0.05). (D) Similar to C except the ratio of menthol to KCl currents in TRPM8-transfected neurons is depicted. Error bars represent SEM, and the menthol to KCl current ratio is significantly decreased after 4 hr exposure to menthol (Student's unpaired t test, p<0.05).
