M channels containing KCNQ2 subunits modulate norepinephrine, aspartate, and GABA release from hippocampal nerve terminals - PubMed (original) (raw)

Effects of RT and FP on K+- evoked release of hippocampal [3H]NE release and on KCNQ2 channels expressed in CHO cells. A, Effects of 10 μ

m

RT on [3H]NE release evoked by increasing [K+]e. The integrated AUCs of hippocampal [3H]NE release were 6.08 ± 0.42, 12.95 ± 0.78, 18.20 ± 1.26, and 23.60 ± 1.65% of total synaptosomal radioactivity with 9, 15, 30, and 50 m

m

[K+]e, respectively. Filled triangles are the percentage of RT (10 μ

m

)-induced inhibition of depolarization-induced [3H]NE release observed at the indicated [K+]e. Data represent the mean ± SEM of three experiments run in triplicate. *p < 0.05 versus respective controls. B, Effect of 10 μ

m

RT on KCNQ2 channels with 2 and 50 m

m

[K+]e. Representative voltage ramp-evoked current traces from a single KCNQ2-transfected cell are recorded in 2 m

m

(thin lines) or 50 m

m

(thick lines) [K+]e. C, Enhancement of KCNQ2 K+ currents by RT and FP is maximal at negative membrane potentials. KCNQ2 K+ currents (2 m

m

[K+]e) were activated by the voltage-ramp protocol described in Materials and Methods under control conditions (C), after exposure to 10 μ

m

RT or to 10 μ

m

FP and after washout (W), as indicated in the inset. After normalization to the maximal value, the currents recorded in the presence of the drug were divided by the control currents, and the results were expressed as a function of membrane potential. The vertical arrows indicate the theoretical _E_K values predicted by the Nernst equation (_E_K = RT/F × ln [K+]e/[K+]i) in the presence of the indicated [K+]e. In, Logarithm. Similar results were obtained in four cells with 10 μ

m

RT and in three cells with 10 μ

m

FP.