[Roles of G Protein-gated Inward Rectifier Potassium Channels in Substance Addiction].

G protein-gated inward rectifier potassium(GIRK)channels are widely distributed in the central nervous system and play important roles in maintaining the resting membrane potential of neurons,adjusting neuronal excitability,and regulating the release of neurotransmitter.Studies have shown that addictive behavior is closely related to the expression and activity of the GIRK channels in the brain reward system and the GIRK channels may be a potential target for addiction treatment.This article summarizes the recent research advances in GIRK channels in terms of structure,intracranial tissue distribution,and especially substance addiction.

Voltage-gated potassium channel blocker 4-aminopyridine induces glioma cell apoptosis by reducing expression of microRNA-10b-5p.

Accumulating evidence has demonstrated that voltage-gated potassium channels (Kv channels) were associated with regulating cell proliferation and apoptosis in tumor cells. Our previous study proved that the Kv channel blocker 4-aminopyridine (4-AP) could inhibit cell proliferation and induce apoptosis in glioma. However, the precise mechanisms were not clear yet. MicroRNAs (miRNAs) are small noncoding RNAs that act as key mediators in the progression of tumor, so the aim of this study was to investigate the role of miRNAs in the apoptosis-promoting effect of 4-AP in glioma cells. Using a microRNA array, we found that 4-AP altered the miRNA expression in glioma cells, and the down-regulation of miR-10b-5p induced by 4-AP was verified by real-time PCR. Transfection of miR-10b-5p mimic significantly inhibited 4-AP-induced caspases activation and apoptosis. Moreover, we verified that apoptosis-related molecule Apaf-1 was the direct target of miR-10b-5p. Furthermore, miR-10b-5p mimic significantly inhibited 4-AP-induced up-regulation of Apaf-1 and its downstream apoptosis-related proteins, such as cleaved caspase-3. In conclusion, Kv channel blocker 4-AP may exert its anti-tumor effect by down-regulating the expression of miR-10b-5p and then raised expression of Apaf-1 and its downstream apoptosis-related proteins. Current data provide evidence that miRNAs play important roles in Kv channels-mediated cell proliferation and apoptosis.

[Effect of Ginsenoside Rg2 and Its Stereoisomers on Oxygen-Glucose Deprivation and Reperfusion Induced Cortical Neuronal Injury Model].

OBJECTIVE: To observe the effect of natural type ginsenoside Rg2 (Rg2) and its stereoisomers [20 (R)-Rg2 and 20 (S)-Rg2] at different concentrations on oxygen-glucose deprivation/ reperfusion (OGD/R) induced cortical neuronal injury model in vitro, and to explore the mechanism, and compare their differences of action. METHODS: Cortical neurons after 7-day culture were randomly divided into 5 groups, i.e., the control group, the model group, the Rg2 group, 20 (R) -Rg2 group, and 20 (S) - Rg2 group. Cortical neurons in the Rg2 group, 20 (R)-Rg2 group, and 20(S)-Rg2 group were pretreated with 20, 40, and 80 µmol/L Rg2, 20 (R) -Rg2, and 20 (S) -Rg2 for 24 h to prepare OGD/R model. The cell survival rate, the activity of Caspase-3, the intracellular Ca2+ concentration, contents of superoxide dismutase (SOD) and malondialdehyde (MDA) were detected 24 h later. RESULTS: Compared with the control group, cell survival rates and activities of SOD obviously decreased, the activity of Caspase-3, Ca2+ fluorescent optical gray value, and contents of MDA significantly increased with statistical difference (P < 0.05). Compared with the model group, cell survival rates and activities of SOD obviously increased, the activity of Caspase-3, Ca2+ fluorescent optical gray value, and contents of MDA significantly decreased in 20 µmol/L Rg2 group, 40 µmol/L 20 (R) -Rg2 group, and 80 µmol/L 20 (S) -Rg2 group (P < 0.05). Compared with 20(S)-Rg2 group, cell survival rates increased and contents of MDA significantly decreased in 20, 40, and 80 µmol/L Rg2 and 20 (R)-Rg2 groups (P < 0.05). The activity of Caspase-3 decreased and contents of SOD increased in 80 µmol/L 20 (R)-Rg2 group, and 40, 80 µmol/L Rg2 groups (P < 0.05). Ca2+ fluorescent optical gray value decreased in 40, 80 µmol/L Rg2 and 20 (R)-Rg2 groups (P < 0.05). Compared with 20 (R)-Rg2 group, Ca2+ fluorescent optical gray value decreased in 80 µmol/L Rg2 group (P < 0.05); contents of SOD increased in 40 and 80 µmol/L Rg2 groups (P < 0.05); contents of MDA decreased in 20, 40, and 80 µmol/L Rg2 groups (P < 0.05). CONCLUSIONS: Rg2 and its stereoisomers could improve cell vitality of cortical neurons against OGD/R induced injury. This might be related to improving anti-apoptotic capacities and antioxidant abilities, and reducing Ca2+ inflow. Besides, the neuroprotective effect of 20 (R) -Rg2 was better than that of 20 (S) -Rg2, but inferior to that of Rg2.

Differential expression of ATP-gated P2X receptors in DRG between chronic neuropathic pain and visceralgia rat models.

There are divergences between neuropathic pain and visceralgia in terms of the duration, location, and character of hyperalgesia. It is generally recognized that nociceptive receptors, including P2X receptors, may play different roles in nociceptive mechanisms. The different roles of P2X1-7 receptors have not been fully understood both in neuropathic pain and visceral hyperalgesia. In order to explore the different expressions of P2X1-7 receptors in these two hyperalgesia models, the lumbosacral dorsal root ganglion (DRG) neurons from rat sciatic nerve chronic constriction injury (CCI) model and neonatal colorectal distention (NCRD) model were studied (both the primary nociceptive neuron afferents of those two models projected to the same segment of spinal cord). Both immunohistochemistry (IHC) technique and real-time fluorescence quantitative polymerase chain reaction (RT-PCR) technology were applied to analyze the protein expression levels and nucleic acid of P2X1-7 receptors. We found that except P2X2 and P2X3, the expression levels of P2X1 and P2X5 receptors increased in neuropathic pain while those expression levels of P2X4, P2X6, and P2X7 receptors increased in visceral pain. Our results also suggested that in addition to P2X2/3 heteromeric, other P2X subunits may also involved in generation heteromeric such as P2X1/5 and/or P2X2/5 in neuropathic pain and P2X4/6 and/or P2X4/7 in visceral pain.

Phenotypes of ATP-activated current associated with their genotypes of P2X1-6 subunits in neurons innervating tooth-pulp.

To explore the association of the phenotype of ATP-activated current with the genotype of P2X1-6 subunits in nociceptors, we developed a method that allows us to label nociceptive neurons innervating tooth-pulp in rat trigeminal ganglion (TG) neurons using a retrograde fluorescence-tracing method, to record ATP-activated current in freshly isolated fluorescence-labeled neurons, and then to conduct single cell immunohistochemical staining for P2X1-6 subunits in the same neuron. We found that fast application of 100 µM ATP to fluorescence-traced TG neurons produced robust inward current in 87% (96/110) of cells tested. The diameter of cells varied from 16 to 56 µm. Three types of ATP-activated current (F, I and S) were recorded with distinct rise times of the current (R10-90, P < 0.05). There was a positive correlation between the cell diameter and the value of R10-90 (P < 0.05): the value of R10-90 increased with increases in the cell diameter. Cells responsive to ATP with the type F current mainly showed positive staining for P2X3 and P2X5, but negative staining for P2X2; cells responsive to ATP with the type I current showed positive staining for P2X1-3 and P2X5, but negative staining for P2X4; and cells responsive to ATP with the type S current showed positive staining for P2X1-5, but negative staining for P2X6. The present findings suggest that in addition to P2X3 subunits, P2X5 subunits are also involved in the generation of the F type of ATP-activated current in small-sized nociceptive neurons. In addition to the P2X2/3 subunit-containing channels, more complex uncharacterized combinations of P2X1-5 subunits exist in native medium-sized nociceptive neurons exhibiting the I and S types of ATP-activated current. In addition, the P2X6 subunit is not a main subunit involved in the nociceptive signal in rat TG neurons innervating tooth-pulp.

Voltage­gated K+ channel blocker quinidine inhibits proliferation and induces apoptosis by regulating expression of microRNAs in human glioma U87­MG cells.

Accumulating evidence has proved that potassium channels (K+ channels) are involved in regulating cell proliferation, cell cycle progression and apoptosis of tumor cells. However, the precise cellular mechanisms are still unknown. In the present study, we investigated the effect and mechanisms of quinidine, a commonly used voltage-gated K+ channel blocker, on cell proliferation and apoptosis of human glioma U87-MG cells. We found that quinidine significantly inhibited the proliferation of U87-MG cells and induced apoptosis in a dose-dependent manner. The results of caspase colorimetric assay showed that the mitochondrial pathway was the main mode involved in the quinidine-induced apoptotic process. Furthermore, the concentration range of quinidine, which inhibited voltage-gated K+ channel currents in electrophysiological assay, was consistent with that of quinidine inhibiting cell proliferation and inducing cell apoptosis. In U87-MG cells treated with quinidine (100 µmol/l), 11 of 2,042 human microRNAs (miRNAs) were upregulated and 16 were downregulated as detected with the miRNA array analysis. The upregulation of miR-149-3p and downregulation of miR-424-5p by quinidine treatment were further verified by using quantitative real-time PCR. In addition, using miRNA target prediction program, putative target genes related to cell proliferation and apoptosis for two differentially expressed miRNAs were predicted. Taken together, these data suggested that the anti-proliferative and pro-apoptosis effect of voltage-gated K+ channel blocker quinidine in human glioma cells was mediated at least partly through regulating expression of miRNAs, and provided further support for the mechanisms of voltage-gated K+ channels in mediating cell proliferation and apoptosis.

[Theoretical Investigation of the Electron Paramagnetic Resonance Parameters and Local Structures for Zinc Phosphate Glass Doped with VO2+].

As an important model system, 3d(1) ions (VO2+, V4+ et al) have been extensively investigated by means of electron paramagnetic resonance (EPR), and many experimental results of EPR parameters were also measured. The optical absorption and EPR parameters (g factors g||, g⊥ and hyperfine structure constants A||, A⊥) of a tetragonal V4+ center in zinc phosphate glass are theoretically investigated, using the perturbation formulas for a 3d(1) ion in tetragonally compressed octahedra. Since the spin-orbit coupling parameter r (150 cm(-1)) of ligand O2- is close to that ξp(0) (≈248 cm(-1)) of the central 3d(1) ion in zinc phosphate glass doped VO2+, the effect of the spin-orbit coupling parameter ξp(0) on the EPR spectra and optical absorption spectra should be taken into account. In this work, the relationship between the EPR parameters as well as the optical absorption spectra and the local structure of the impurity center are established based on the superposition model. By fitting the calculated EPR parameters and optical absorption spectra for V4+ center in zinc phosphate glass to the experimental data, the local structure parameters of [VO6](8-) cluster are obtained. According to the investigation, the magnitudes of the metal-ligand distances parallel and perpendicular to the C4-axis of [VO6](8-) cluster are, respectively, R|| ≈ 0.175 nm and R⊥ ≈ 0.197 nm, the local structure around the V4+ ions possesses a compressed tetragonal distortion along C4 axis. Theoretical results of EPR parameters and optical absorption spectra are in good agreement with experimental data, the validity of the calculated results has also been discussed. Thus, perturbation method is effective to the studies the EPR parameters and optical spectra of transition-metal 3d ions in crystals. In addition, based on the studies of the hyperfine structure constants (All and A1), one can found that the large value of kappa indicates a large contribution to the hyperfine constant by the unpaired selectron.

Voltage-gated and ATP-sensitive K+ channels are associated with cell proliferation and tumorigenesis of human glioma.

Increasing evidence indicates that potassium (K+) channels play important roles in the growth and development of human cancer. In the present study, we investigated the contribution of and the mechanism by which K+ channels control the proliferation and tumor development of U87-MG human glioma cells. A variety of K+ channel blockers and openers were used to differentiate the critical subtype of K+ channels involved. The in vitro data demonstrated that selective blockers of voltage-gated K+ (K(V)) channels or ATP-sensitive K+ (K(ATP)) channels significantly inhibited the proliferation of U87-MG cells, blocked the cell cycle at the G0/G1 phase and induced apoptosis. In the U87-MG xenograft model in nude mice, K(V) or K(ATP) channel blockers markedly suppressed tumor growth in vivo. Furthermore, electrophysiological results showed that KV or KATP channel blockers inhibited K(V)/K(ATP) channel currents as well as cell proliferation and tumor growth over the same concentration range. In contrast, iberiotoxin, a selective blocker of calcium-activated K+ channels, had no apparent effect on the cell proliferation, cell cycle or apoptosis of U87-MG cells. In addition, the results of fluorescence assays indicated that blockers of K(V) or K(ATP) channels attenuated intracellular Ca2+ signaling by blocking Ca2+ influx in U87-MG cells. Taken together, these data suggest that K(V) and K(ATP) channels play important roles in the proliferation of U87-MG cells and that the influence of K(V) and K(ATP) channels may be mediated by a Ca2+-dependent mechanism.

P2X3, but not P2X1, receptors mediate ATP-activated current in neurons innervating tooth-pulp.

We developed a method that allows us to label nociceptive neurons innervating tooth-pulp in rat trigeminal ganglion neurons using a retrograde fluorescence-tracing method, to record ATP-activated current in freshly isolated fluorescence-labeled neurons and to conduct single cell immunohistochemical staining for P2X1 and P2X3 subunits in the same neuron. Three types of ATP-activated current in these neurons (F, I and S) were recorded. The cells exhibiting the type F current mainly showed positive staining for P2X3, but negative staining for P2X1. The results provide direct and convincing evidence at the level of single native nociceptive neurons for correlation of the characteristics of ATP-activated currents with their composition of P2X1 and P2X3 subunits and cell size. The results also suggest that the P2X3, but not P2X1, is the main subunit that mediates the fast ATP-activated current in nociceptive neurons.

Conserved extracellular cysteines differentially regulate the potentiation produced by Zn2+ in rat P2X4 receptors.

One feature of the amino acid sequence of P2X receptors identified from mammalian species, Xenopus laevis and zebrafish is the conservation of ten cysteines in the extracellular loop. Little information is available about the role of these conserved ectodomain cysteines in the function of P2X receptors. Here, we investigated the possibility that ten conserved cysteine residues in the extracellular loop of the rat P2X4 receptor may regulate zinc potentiation of the receptor using a series of individual cysteine to alanine point mutations and functional characterization of recombinant receptors expressed in Xenopus oocytes. For the C116A, C132A, C159A, C165A, C217A and C227A mutants, 10 µM zinc did not significantly affect the current activated by an EC40 concentration of ATP. By contrast, 5 µM zinc shifted the ATP concentration-response curve to the right in a parallel manner for both the C261A and C270A mutants and the magnitudes of those shifts were similar to that of the wildtype receptor. Interestingly, for the C126A and C149A mutants, 5µM zinc potentiated ATP-activated current, but increased the maximal response to ATP by 90% and 81% respectively, without significantly changing the EC50 value of ATP. Thus, these results suggest that cysteines and disulfide bonds between cysteines are differentially involved in the potentiation of the rat P2X4 receptor by zinc.

[The study of removing salt in salt Aconiti Lateralis Radix Praeparata].

OBJECTIVE: To study the method and technique to remove the salt of salt Aconiti Lateralis Radix Praeparata. METHODS: Took the Aconiti Lateralis Radix Praeparata alkaloids, polysaccharides and the content of removing salt as the indexes, and then compared with the original process. RESULTS: There was no obvious difference between these two way on the content of the Aconiti Lateralis Radix Praeparata alkaloids and polysaccharides,and the time of removing salt has reduced from 7 days (168 h) to 1.5 h. CONCLUSION: The new way reduces the time to remove salt obviously, and saves water; The research fills in the gaps of removing the salt of salt Aconiti Lateralis Radix Praeparata and provides thought and method for processing technology of Aconiti Lateralis Radix Praeparata

Potentiation by WIN 55,212-2 of GABA-activated currents in rat trigeminal ganglion neurones.

BACKGROUND AND PURPOSE: Although both natural and synthetic cannabinoid compounds have been shown to exert an antinociceptive effect on acute and persistent pain, the anatomical locus of the target of cannabinoid-induced analgesia has not been fully elucidated. Here, we investigated the effects of the cannabinoid agonist WIN 55,212-2 on GABA-activated currents (I(GABA)) in rat primary sensory neurones. EXPERIMENTAL APPROACH: In the present study, experiments were performed on neurones freshly isolated from rat trigeminal ganglion (TG) by using whole-cell patch clamp and repatch techniques. KEY RESULTS: GABA-evoked inward currents were potentiated by pretreatment with WIN 55,212-2 in a concentration-dependent manner (10(-10)-10(-8) M). WIN 55,212-2 shifted the GABA concentration-response curve upwards, with an increase of 30.3 +/- 3.7% in the maximal current response but with no significant change in the EC(50) (agonist concentration producing a half-maximal response) value. WIN 55,212-2 potentiated the responses to GABA in a manner independent of holding potential and in the absence of any change in the reversal potential of the current. This potentiation of I(GABA) induced by WIN 55,212-2 was almost completely blocked by AM 251 (3 x 10(-8) M), a CB(1) receptor antagonist, and, using the repatch technique, was found to be abolished after intracellular dialysis with the protein kinase A (PKA) activator cAMP or the PKA inhibitor H89. CONCLUSIONS AND IMPLICATIONS: The potentiation by WIN 55,212-2 of I(GABA) in primary sensory neurones may help to elucidate the mechanism underlying the modulation of analgesia by cannabinoids in the spinal dorsal horn.

Effect of composite salvia injection on platelet parameters in children with anaphylactoid purpura.

OBJECTIVE: To explore the effect of composite salvia injection (CSI) on platelet parameters in children with anaphylactoid purpura (AP) and its clinical significance. METHODS: One hundred and fifty children with AP were assigned to two groups, 80 in Group A and 70 in Group B. They were treated, respectively, with conventional therapy only or conventional therapy combined with CSI. Their platelet parameters, including blood platelet count (BPC), mean platelet volume (MPV), platelet distribution width (PDW) and plateletcrit (PCT) were determined at the acute stage and convalescent stage, respectively. RESULTS: At the acute stage, the BPC in AP children of both groups was in the normal range, but significant abnormality was shown in the levels of MPV, PDW and PCT. As for comparisons of these parameters at the convalescent stage, significant difference between the two groups was also shown in terms of MPV, PDW and PCT (P<0.05 or P<0.01). CONCLUSION: Although platelet shows no quantitative change in the pathogenic process of AP, important functional changes are surely existent. CSI could promote the normalization of platelet function.

Mechanism of bis(7)-tacrine inhibition of GABA-activated current in cultured rat hippocampal neurons.

Bis(7)-tacrine is a novel dimeric acetylcholinesterase inhibitor derived from tacrine that shows promise for the treatment of Alzheimer's disease. We have previously reported that bis(7)-tacrine inhibits GABA(A) receptors. In the present study we investigated the mechanism of bis(7)-tacrine inhibition of GABA(A) receptor function using whole-cell patch-clamp recording in cultured rat hippocampal neurons. Bis(7)-tacrine produced a gradual decline of GABA-activated current to a steady-state, but this was not an indication of use-dependence, as the gradually declining component could be eliminated by exposure to bis(7)-tacrine prior to GABA application. In addition, bis(7)-tacrine inhibition did not require the presence of agonist, and GABA-activated current recovered completely from inhibition by bis(7)-tacrine in the absence of agonist. The slow onset of inhibition by bis(7)-tacrine was not apparently due to an action at an intracellular site, as inclusion of 25 microM bis(7)-tacrine in the recording pipette did not alter inhibition by bis(7)-tacrine applied externally. Bis(7)-tacrine shifted the GABA concentration-response curve to the right in a parallel manner and the pA(2) value estimated from a Schild plot was 5.7. Bis(7)-tacrine increased the time constant of activation of GABA-gated ion channels without affecting the time constants of deactivation or desensitization. These results suggest that bis(7)-tacrine is a competitive GABA(A) receptor antagonist with slow onset and offset kinetics. The competitive inhibition of GABA receptors by bis(7)-tacrine could contribute to its ability to enhance memory.

Conserved extracellular cysteines differentially regulate the inhibitory effect of ethanol in rat P2X4 receptors.

Relatively little information is available about the molecular mechanism of ethanol inhibition of P2X receptors. Here, we investigated the possibility that 10 conserved cysteine residues in the extracellular loop of the rat P2X4 receptor may regulate ethanol inhibition of the receptor using a series of individual cysteine to alanine point mutations. Each of the mutated receptors generated robust inward current in response to ATP and the mutations produced less than a sixfold change in the ATP EC50 value. For the C116A, C126A, C149A, and C165A mutants, 100 mM ethanol did not significantly affect the current activated by an EC40 concentration of ATP. By contrast, for the C261A and C270A mutants, ethanol inhibited ATP-activated current in a competitive manner similar to that for the wild-type receptor. Interestingly, for the C132A, C159A, C217A, and C227A mutants, ethanol inhibited ATP-activated current, but decreased the maximal response to ATP by 70-75% without significantly changing the EC50 value of ATP, thus exhibiting a noncompetitive-type inhibition. The results suggest that cysteines and disulfide bonds between cysteines are differentially involved in the inhibition of the rat P2X4 receptor by ethanol.

Inhibition of NMDA-gated ion channels by bis(7)-tacrine: whole-cell and single-channel studies.

Bis(7)-tacrine is a novel dimeric acetylcholinesterase inhibitor derived from tacrine, and has been proposed as a promising agent to treat Alzheimer's disease. We have recently reported that bis(7)-tacrine prevents glutamate-induced neuronal apoptosis by antagonizing NMDA receptors. The purpose of this study was to characterize bis(7)-tacrine inhibition of NMDA-activated current by using patch-clamp recording techniques. In cultured rat hippocampal neurons, bis(7)-tacrine inhibited NMDA-activated whole-cell current in a concentration-dependent manner with an IC(50) of 0.66+/-0.07 microM. Bis(7)-tacrine produced a gradual decline of NMDA-activated current to a steady-state, but this was not an indication of use-dependence. Also, the slow onset of inhibition by bis(7)-tacrine was not apparently due to an action at an intracellular site. Bis(7)-tacrine, 0.5 microM, decreased the maximal response to NMDA by 40% without changing its EC(50). Bis(7)-tacrine inhibition of NMDA-activated current was not voltage-dependent, and was independent of glycine concentration. Results of single-channel experiments obtained from cells expressing NR1 and NR2A subunits revealed that bis(7)-tacrine decreased the open probability and frequency of channel opening, but did not significantly alter the mean open time or introduce rapid closures. These results suggest that bis(7)-tacrine can inhibit NMDA receptor function in a manner that is slow in onset and offset and noncompetitive with respect to both NMDA and glycine. The noncompetitive inhibition of NMDA receptors by bis(7)-tacrine could contribute to its protective effect against glutamate-induced neurotoxicity.

Bis(7)-tacrine prevents glutamate-induced excitotoxicity more potently than memantine by selectively inhibiting NMDA receptors.

We have recently reported that bis(7)-tacrine could prevent glutamate-induced neuronal apoptosis through NMDA receptors. In this study, we demonstrated that in cultured rat cortical neurons, bis(7)-tacrine (IC(50), 0.02 microM) prevented glutamate-induced excitotoxicity more substantially than memantine (IC(50), 0.7 microM). In addition, bis(7)-tacrine was more efficient than memantine in buffering the intracellular Ca(2+) triggered by glutamate. In cultured rat hippocampal neurons, bis(7)-tacrine inhibited 50 microM NMDA-activated current in a concentration-dependent manner with an IC(50) of 0.68+/-0.07 microM, which is five times more potent than that produced by memantine (IC(50), 3.41+/-0.36 microM; p<0.05). By contrast, bis(7)-tacrine, up to 5 microM, did not significantly affect the current activated by 50 microM AMPA or 50 microM kainate. These results suggest that bis(7)-tacrine is more potent than memantine against glutamate-induced neurotoxicity by selectively inhibiting NMDA-activated current.

Inhibition by bis(7)-tacrine of native delayed rectifier and KV1.2 encoded potassium channels.

Bis(7)-tacrine [bis(7)-tetrahydroaminacrine] acts as an AChE inhibitor and also exerts modulatory effects on many ligand-gated ion channels and voltage-gated Ca(2+) and K(+) channels. It has been reported previously that tacrine and some other AChE inhibitors suppressed I(K(A)) in central and peripheral neurons. The present study aimed to explore whether bis(7)-tacrine could modulate the function of native delayed rectifier potassium channels in DRG neurons and K(V)1.2 encoded potassium channels expressed in oocytes. We found that both delayed rectifier potassium currents (I(K(DR))) in rat DRG neurons and the currents recorded from oocytes expressing K(V)1.2 (I(K(K(V)1.2))) were suppressed by bis(7)-tacrine, the potency of which was two orders greater than that of tacrine. The IC(50) values for bis(7)-tacrine and tacrine inhibition of I(K(KD)) in DRG neurons were 0.72+/-0.05 and 58.3+/-3.7 microM, respectively; while the two agents inhibited I(K(K(V)1.2)) in oocytes with an IC(50) of 0.24+/-0.06 and 102.1+/-21.5 microM, respectively. The possible mechanism for bis(7)-tacrine inhibition of I(K(A)) and I(K(K(V)1.2)) was identified as the suppression of their activation, inactivation.