Fig. 7.
Effect of L-bupivacaine and D-bupivacaine on excitatory postsynaptic currents evoked by noxious and innocuous mechanical stimuli in female rats. (A) Representative effects of L-bupivacaine (50 μM) on pinch-evoked excitatory postsynaptic currents recorded from substantia gelatinosa neurons. The pinch-evoked excitatory postsynaptic currents were reduced in the presence of L-bupivacaine. (B) Representative effects of D-bupivacaine (50 μM) on pinch-evoked excitatory postsynaptic currents recorded from substantia gelatinosa neurons. The pinch-evoked excitatory postsynaptic currents were reduced in the presence of D-bupivacaine. (C) Representative effects of L-bupivacaine (50 μM) on brush-evoked excitatory postsynaptic currents recorded from deep dorsal horn neurons. The brush-evoked excitatory postsynaptic currents were hardly changed in the presence of L-bupivacaine. (D) Representative effects of D-bupivacaine (50 μM) on brush-evoked excitatory postsynaptic currents recorded from deep dorsal horn neurons. The brush-evoked excitatory postsynaptic currents were reduced in the presence of D-bupivacaine. (E) Summary of the inhibition ratio of L-bupivacaine (n = 6, **P = 0.001) and D-bupivacaine (n = 6, **P = 0.002) on the area of pinch-evoked excitatory postsynaptic currents. Data presented as mean ± SD. (F) Summary of the inhibition ratio of L-bupivacaine (n = 5, P = 0.235) and D-bupivacaine (n = 5, ***P < 0.001) on the area of brush-evoked excitatory postsynaptic currents. Data presented as mean ± SD. (G) Effect of L-bupivacaine and D-bupivacaine on miniature excitatory postsynaptic currents. In the presence of tetrodotoxin (0.5 μM), L-bupivacaine and D-bupivacaine did not affect the frequency (L-bupivacaine: n = 6, P = 0.974; D-bupivacaine: n = 6, P = 0.973) or amplitude (L-bupivacaine: n = 6, P = 0.803; D-bupivacaine: n = 6, P = 0.955) of miniature excitatory postsynaptic currents. Cumulative distributions of the interevent interval and amplitude of miniature excitatory postsynaptic currents were shown. Both L-bupivacaine (red line) and D-bupivacaine (blue line) did not change the interevent interval (P = 0.977 and P = 0.961, respectively, Kolomogorov–Smirnov test) and amplitude (P = 0.803 and P = 0.955, respectively, Kolomogorov–Smirnov test) of miniature excitatory postsynaptic currents.