PURPOSE: Flutamide (4-nitro-3-t-trifluoromethyl-isobutyranilide) is an androgen-receptor antagonist with typical antiandrogenic effect, used to treat androgen-dependent disorders such as prostate cancer. However, some reports noted that flutamide has direct effects to neuronal cells. It has been shown to retard the development of electrical kindling in rats. METHODS: We used the chemoconvulsant 4-aminopyridine (4-AP) and picrotoxin (PTX) in the in vitro hippocampal slice model to determine of flutamide for the suppression of epileptiform discharges. Extracellular field potential recordings were obtained from the CA3 pyramidal layer of hippocampus. RESULTS: The concentration of 30 and 100 micrometer flutamide suppressed the whole mean number of epileptiform discharges to 57.8% and 66.8% each compared with the 4-AP only slices. In 100 micrometer PTX, 10 and 30 micrometer flutamide suppressed the whole mean number of epileptiform discharges to 56.6% and 82.5% each. Intermixed with flumazenil, the anticonvulsant effect of flutamide was decreased. CONCLUSIONS: Flutamide suppressed epileptiform discharges induced by 4-AP and PTX in vitro seizure model. It suggests that flutamide influence to anti-epileptic activity by benzodiazepine site of the GABAA receptor.
4-Aminopyridine ; Benzodiazepines ; Flumazenil ; Flutamide ; Neurons ; Picrotoxin ; Prostatic Neoplasms ; Seizures

PURPOSE: In order to elucidate the actual mechanism and the optimal concentration of Lamotrigine(LTG) that suppresses epileptiform discharges, we observed epileptiform discharges from hippocampal slices of immature rat in 4-aminopyridine(4-AP) added Mg2+ - free medium of artificial cerebrospinal fluid(aCSF) with various LTG concentrations. METHODS: We divided 19-23 day-old Sprague-Dawley rats into 4 groups; control group(n=12) and 3 LTG groups depending on the concentrations of LTG such as 400 (n=9), 800(n=7), and 1,000(n=8) microM. The rats were anesthetized and their brains were taken, soaked in aCSF(NaCl 125 mM, KCl 2.5 mM, NaH2PO4 2 mM, MgSO4 1.25 mM NaHCO3 25 mM, CaCl2 2 mM, Glucose 10 mM, pH 7.3-7.4). And then the brains were cut into 400 microm hippocampal slices by a vibratome. The slices of control group were soaked in 200 microM 4-AP added Mg2+ -free medium of aCSF for 1 hour, and then extracellular recordings were performed in hippocampal CA1 pyramidal region. The slices of LTG groups were soaked in the solution containing 400, 800, and 1,000 microM LTG, then extracellular recordings were performed. RESULTS: Interictal discharges were observed in all the control and the LTG groups. The latency to the first interictal discharges after 4-AP addition was 52.7+/-26.9 sec in control group, but was 225.0+/-28.2 sec in 800 microM and 322.1+/-116.4 sec in 1,000 microM group of LTG(P<0.05). The duration of interictal discharges was 64.6+/-35.6 sec in control group, but was the shortest in 800 microM group of LTG at 39.3+/-12.6 sec. Ictal discharges were observed in all of control and 400 microM group, but the frequency was decreased as the concentration of LTG increases, 57.1% in 800 microM, 12.5% in 1,000 microM group. The latency to ictal discharge after 4-AP addition was 142.1+/-52.6 sec in control group, but increased as the concentration of LTG increases, 304.4+/-84.5 sec in 400 microM group and 689.8+/-213.1 sec in 800 microM group(P<0.05). The duration of ictal discharges was 1,534.7/-339.3 sec in control group, but decreased as the concentration of LTG increases, it was 126.5+/-76.1 sec in 800 microM group(P <0.05) and 42 sec in 1,000 microM group. CONCLUSION: The antiepileptic effects of LTG were most significant when the concentration, inhibiting epileptiform discharges induced by 4-AP and Mg2+ -free medium in hippocampal slices of immature rats, was 800 microM or higher. Although the basic pharmacologic mechanism of LTG is the inhibition of sodium channel, it may also work on potassium channel at higher concentrations.
4-Aminopyridine* ; Animals ; Brain ; Glucose ; Hydrogen-Ion Concentration ; Potassium Channels ; Rats* ; Rats, Sprague-Dawley ; Sodium Channels

BACKGROUND: Long-term phenytoin therapy induces resistance to the neuromuscular blocking effects of metocurine, atracurium, doxacurium, and pipecuronium. This study examine neuromuscu-lar blocking effect and recovery of mivacurium in isolated rat phrenic-hemidiaphragm with two-weeks phenytoin pretreatment. METHOD: After the administration of 14 days of phenytoin 40 mg/kg, administered intraperitoneally twice daily (n=10), ED90, antagonism of neostigmine and 4-aminopyridine on the electrically evoked twitch response and train-of-four (TOF) stimulation were compared to control groups in isolated rat phrenic-hemidiaphragm preparation. RESULTS: ED90 was significantly greater in the phenytoin group than in the control group (319 +/- 39.5 g vs. 209.5 +/- 52.2 g, respectively). After the administration of neostigmine 0.75 M, the recovery of the single twitch and TOF ratio were significantly lesser in the phenytoin group than in the control group (single twitch; 19.6 +/- 6.6% vs. 69.2 +/- 9.4%, TOF ratio; 0.258 +/- 0.149 vs. 0.543 +/- 0.1, respectively). After the administration of 4-aminopyridine 40uM, the recovery of the single twitch and TOF ratio were no significant differrence between the phenytoin group and the control group (twitch; 118.1 +/- 25.3% vs. 122.6 +/- 24.8%, TOF ratio; 0.937 +/- 0.051 vs. 0.949 +/- 0.067, respectively). CONCLUSION: Long-term phenytoin therapy induces resistance to the neuromuscular blocking effects of mivacurium.
4-Aminopyridine ; Animals ; Atracurium ; Drug Interactions ; Neostigmine ; Neuromuscular Blockade* ; Phenytoin* ; Pipecuronium ; Rats*

BACKGROUND: The aim of this study was to evaluate the effect of 4-aminopyridine (4-AP) combined with anticholiesterase (antiChE) in antagonizing MgSO4-rocuronium-induced neuromuscualr blockade using a rat hemidiaphragm. METHODS: A hemidiaphragm with phrenic nerve was dissected and was mounted in a bath containing oxygenated Krebs solution. The phrenic nerve was stimulated supramaximally and the twitch response (0.1 Hz) was stabilized for at least 30 minutes. After maximal twitch inhibition by IC95 (concentration of 95% twitch inhibition) of rocuronium and MgSO4 20 mg was achieved, antagonistic effects of 1.6, 16 microgram/ml of edrophonium, 0.1, 1.0 microgram/ml of neostigmine, 0.5, 5.0 microgram/ml of pyridostigmine, and 0.8 microgram/ml of 4-AP combined with each of the above mentioned antiChEs were investigated. RESULTS: Whereas antiChE alone at low concentration partially recovered only the twitch response, 4-AP combined with antiChE recovered both the twitch and train-of-four responses significantly. CONCLUSIONS: 4-AP enhances antagonism of a magnesium-rocuronium induced neuromuscular blockade by edrophonium, neostigmine or pyridostigmine in vitro.
4-Aminopyridine* ; Animals ; Baths ; Cholinesterase Inhibitors* ; Edrophonium ; Neostigmine ; Neuromuscular Blockade* ; Oxygen ; Phrenic Nerve ; Pyridostigmine Bromide ; Rats

Acute hypoxia induces contraction of pulmonary artery (PA) to protect ventilation/perfusion mismatch in lungs. As for the cellular mechanism of hypoxic pulmonary vasoconstriction (HPV), hypoxic inhibition of voltage-gated K+ channel (Kv) in PA smooth muscle cell (PASMC) has been suggested. In addition, our recent study showed that thromboxane A2 (TXA2) and hypoxia-activated nonselective cation channel (I(NSC)) is also essential for HPV. However, it is not well understood whether HPV is maintained in the animals exposed to ambient hypoxia for two days (2d-H). Specifically, the associated electrophysiological changes in PASMCs have not been studied. Here we investigate the effects of 2d-H on HPV in isolated ventilated/perfused lungs (V/P lungs) from rats. HPV was almost abolished without structural remodeling of PA in 2d-H rats, and the lost HPV was not recovered by Kv inhibitor, 4-aminopyridine. Patch clamp study showed that the hypoxic inhibition of Kv current in PASMC was similar between 2d-H and control. In contrast, hypoxia and TXA2-activated I(NSC) was not observed in PASMCs of 2d-H. From above results, it is suggested that the decreased I(NSC) might be the primary functional cause of HPV disappearance in the relatively early period (2 d) of hypoxia.
4-Aminopyridine ; Animals ; Anoxia* ; Lung ; Muscle Cells* ; Myocytes, Smooth Muscle ; Pulmonary Artery ; Rats* ; Thromboxane A2 ; Vasoconstriction*

The effects of Zn2+ on spontaneous glutamate and GABA release were tested in mechanically dissociated rat CA3 pyramidal neurons which retained functional presynaptic nerve terminals. The spontaneous miniature excitatory and inhibitory postsynaptic currents (mEPSCs and mIPSCs, respectively) were pharmacologically isolated and recorded using whole-cell patch clamp technique under voltage-clamp conditions. Zn2+ at a lower concentration (30 micrometer) increased GABAergic mIPSC frequency without affecting mIPSC amplitude, but it decreased both mIPSC frequency and amplitude at higher concentrations (> or =300 micrometer). In contrast, Zn2+ (3 to 100 micrometer) did not affect glutamatergic mEPSCs, although it slightly decreased both mIPSC frequency and amplitude at 300 micrometer concentration. Facilitatory effect of Zn2+ on GABAergic mIPSC frequency was occluded either in Ca2+ -free external solution or in the presence of 100 micrometer 4-aminopyridine, a non-selective K+ channel blocker. The results suggest that Zn2+ at lower concentrations depolarizes GABAergic nerve terminals by blocking K+ channels and increases the probability of spontaneous GABA release. This Zn2+ -mediated modulation of spontaneous GABAergic transmission is likely to play an important role in the regulation of neuronal excitability within the hippocampal CA3 area.
4-Aminopyridine ; Animals ; gamma-Aminobutyric Acid* ; Glutamic Acid ; Hippocampus ; Inhibitory Postsynaptic Potentials ; Neurons* ; Rats* ; Zinc*

The profile of membrane currents was investigated in differentiated neuronal cells derived from human neural stem cells (hNSCs) that were obtained from aborted fetal cortex. Whole-cell voltage clamp recording revealed at least 4 different currents: a tetrodotoxin (TTX)-sensitive Na+ current, a hyperpolarization-activated inward current, and A-type and delayed rectifier-type K+ outward currents. Both types of K+ outward currents were blocked by either 5 mM tetraethylammonium (TEA) or 5 mM 4-aminopyridine (4-AP). The hyperpolarization-activated current resembled the classical K+ inward current in that it exhibited a voltage-dependent block in the presence of external Ba2+ (30micrometer) or Cs+ (3micrometer). However, the reversal potentials did not match well with the predicted K+ equilibrium potentials, suggesting that it was not a classical K+ inward rectifier current. The other Na+ inward current resembled the classical Na+ current observed in pharmacological studies. The expression of these channels may contribute to generation and repolarization of action potential and might be regarded as functional markers for hNSCs-derived neurons.
4-Aminopyridine ; Action Potentials ; Humans ; Membranes ; Neural Stem Cells ; Neurons ; Tetraethylammonium ; Tetrodotoxin

We have investigated the two types of voltage-dependent outward potassium (K) currents, i.e. delayed rectifier K current (I-K(V)) and 'A-like' transient outward K current (I-to) with patch-clamp technique in single smooth muscle cells (SMCs) isolated from rabbit basilar artery, and investigated the characteristics of them. The time-courses of activation were well fitted by exponential function raised to second power (n-2) in I-K(v) and fourth power (n-4) in I-to. The activation, inactivation and recovery time courses of I-to were much faster than that of I-K(V). The steady-state activation and inactivation of I-K(V) was at the more hyperpolarized range than that of I-to contrary to the reports in other vascular SMCs. Tetraethylammonium chloride (TEA; 10 mM) markedly inhibited I-K(V) but little affected 1-to. 4-Aminopyridine (4-AP) had similar inhibitory potency on both currents. While a low concentration of Cd-2+ (0.5 mM) shifted the current-voltage relationship of I-to to the positive direction without change of maximum conductance, Cd-2+ did not cause any appreciable change for I-K(V).
4-Aminopyridine ; Basilar Artery* ; Muscle, Smooth* ; Myocytes, Smooth Muscle* ; Patch-Clamp Techniques ; Potassium* ; Tetraethylammonium

BACKGROUND: A toxic dose of bupivacaine produces vasodilation in isolated aortas. The goal of this in vitro study was to investigate the cellular mechanism associated with bupivacaine-induced vasodilation in isolated endotheliumdenuded rat aortas precontracted with phenylephrine. METHODS: Isolated endothelium-denuded rat aortas were suspended for isometric tension recordings. The effects of nifedipine, verapamil, iberiotoxin, 4-aminopyridine, barium chloride, and glibenclamide on bupivacaine concentration-response curves were assessed in endothelium-denuded aortas precontracted with phenylephrine. The effect of phenylephrine and KCl used for precontraction on bupivacaine-induced concentration-response curves was assessed. The effects of verapamil on phenylephrine concentration-response curves were assessed. The effects of bupivacaine on the intracellular calcium concentration ([Ca2+]i) and tension in aortas precontracted with phenylephrine were measured simultaneously with the acetoxymethyl ester of a fura-2-loaded aortic strip. RESULTS: Pretreatment with potassium channel inhibitors had no effect on bupivacaine-induced relaxation in the endothelium-denuded aortas precontracted with phenylephrine, whereas verapamil or nifedipine attenuated bupivacaine-induced relaxation. The magnitude of the bupivacaine-induced relaxation was enhanced in the 100 mM KCl-induced precontracted aortas compared with the phenylephrine-induced precontracted aortas. Verapamil attenuated the phenylephrine-induced contraction. The magnitude of the bupivacaine-induced relaxation was higher than that of the bupivacaine-induced [Ca2+]i decrease in the aortas precontracted with phenylephrine. CONCLUSIONS: Taken together, these results suggest that toxic-dose bupivacaine-induced vasodilation appears to be mediated by decreased calcium sensitization in endothelium-denuded aortas precontracted with phenylephrine. In addition, potassium channel inhibitors had no effect on bupivacaine-induced relaxation. Toxic-dose bupivacaine- induced vasodilation may be partially associated with the inhibitory effect of voltage-operated calcium channels.
4-Aminopyridine ; Animals ; Aorta* ; Barium ; Bupivacaine ; Calcium Channels ; Calcium* ; Glyburide ; Nifedipine ; Phenylephrine* ; Potassium Channels ; Rats* ; Relaxation ; Vasodilation* ; Verapamil

PURPOSE: Topiramate(TPM), one of the newest antiepileptic drugs, has been prescribed not only to refractory partial seizures but to generalized tonic-clonic seizures. However, its action mechanisms are not well understood and the optimal dose of antiepileptic efficacy in animal seizure models is not determined yet. In order to elucidate the action mechanisms and the optimal concentration of TPM that suppresses epileptic discharges, we observed ictal and interictal discharges from immature rat hippocampal slices in Mg(2+)-free, and 4-aminopyridine(AP) added artificial CSF with various TPM concentrations. METHODS: We divided Sprague-Dawley rats of 19 to 23 days old into 5 groups; namely, a control group(n=12) and 4 TPM groups according to the concentration of TPM, 6 (n=11), 20(n=7), 60(n=10), and 200(n=14) micrometer. The rats were anesthetized and their brains were taken, and soaked in artificial CSF(NaCl 125 mM; KCl 2.5 mM; NaH2PO4 2 mM; MgSO4 1.25 mM; NaHCO3 25 mM; CaCl2 2 mM, Glucose 10 mM, and pH 7.3-7.4). Then the brains were cut into 400 micrometer hippocampal slices by a vibratome. The slices of the control group were soaked in 200 micrometer 4-AP added Mg(2+)-free medium for 1 hour, and then extracellular recordings were performed in the hippocampal CA1 pyramidal region. The slices of TPM groups were soaked in solutions containing 6, 20, 60, 200 micrometer TPM, and then extracellular recordings were performed. RESULTS: Interictal discharges were observed in the control group and 6, 20 micrometer groups but the frequency decreased as the concentration of TPM increased:90% in 60 micrometer group, and 35.7% in 200 micrometer group. And the amplitude of TPM groups was much smaller than that of the control group. The latency to the first interictal discharge after 4-AP addition was 52.7+/-7.5 sec in the control group, 290.2+/-78 sec in 60 micrometer group, and 568+/-113.1 sec in 200 micrometer group. Duration of the interictal discharge was 64.6+/-10.3 sec in the control group, but was prolonged to 141+/-38.1 sec in 60 micrometer group(P<0.05). Ictal discharges were observed in all of the control and 6 micrometer groups, but the frequency decreased as the concentration of TPM increased:55.6% in 60 micrometer, and 28.6% in 200 micrometer groups. The amplitude of the TPM groups was much smaller than that of the control group. The latency to ictal discharges after 4-AP addition was 141+/-15.2 sec in the control group, but increased as the concentration of TPM increased:431.8+/-57.4 sec in 60 micrometer, and 627.8+/-143.5 sec in 200 micrometer group(P<0.05). The duration of ictal discharges was 1,534.7+/-97.9 sec in the control group, but decreased as the concentration of TPM increased, the shortest in 60 micrometer group, 155.2+/-65.5 sec(P<0.05). Status epilepticus was seen in 58.3% of the control and 27.2% of 6 microM groups. CONCLUSION: TPM suppresses the frequency, latency, and duration of epileptiform discharges induced by Mg(2+)-free, and 4-AP added artificial CSF in immature rat hippocampal slices, starting from 20 micrometer and reaching the maximal effect at over 60 micrometereter. This finding is presumably due to TPM enhancing of GABA receptor currents and/or K+ channel conductance in response to TPM.
4-Aminopyridine* ; Animals ; Anticonvulsants ; Brain ; Glucose ; Hydrogen-Ion Concentration ; Rats* ; Rats, Sprague-Dawley ; Receptors, GABA ; Seizures ; Status Epilepticus