Characteristics of the electrical response to dopamine in neuroblastoma cells

Three-dimensional directional nerve guide conduits fabricated by dopamine-functionalized conductive carbon nanofibre-based nanocomposite ink printing

Directional growth induced by dopamine-functionalized CNF-based nanocomposite ink printing.

Effect of culture age on the susceptibility of differentiating neuroblastoma cells to retinoid cytotoxicity

The cytotoxic effects of retinoids on neuroblastoma cells at various times during electrophysiological differentiation were evaluated. We used N1E-115, a clone of the murine neuroblastoma C1300 derived from the neural crest, and three retinoids: vitamin A (retinol), all-trans retinoic acid (tretinoin), and 13-cis-retinoic acid (isotretinoin). Differentiating N1E-115 cells exposed to retinoids at an isotretinoin EC(50) of 16 microM exhibited the greatest vulnerability in terms of cell death during a period (8 to 10 days) that was previously found to be the most sensitive for induction of gross malformations in rodents. This finding suggested possible similarities between the in vivo and in vitro retinoid mechanism(s) of action. The greatest period of vulnerability to retinoid cytotoxicity was also found to coincide with the rapid resting membrane potential (V(m)) development period, suggesting a linkage between neuronal V(m) and/or electrical excitability development and vulnerability to retinoid cytotoxicity.

Haloperidol causes cytoskeletal collapse in N1E-115 cells through tau hyperphosphorylation induced by oxidative stress: Implications for neurodevelopment

Haloperidol a typical antipsychotic commonly used in the treatment of schizophrenia causes neuronal damage and extrapiramidal symptoms after several years of treatment. These symptoms have been associated with increased levels of oxidative stress. Reactive oxygen species produce cytoskeletal collapse and an excessive phosphorylation of tau, a microtubule-associated protein that plays a key role in microtubule stabilization, and in growth cone and neurite formation, which are cytoskeletal phenotypes that participate in neurodevelopment. Thus, we hypothesized that haloperidol produces neurocytoskeletal disorganization by increasing free radicals and tau hyperphosphorylation, and consequently, the loss of neurodevelopmental cytoskeletal phenotypes, neurites and growth cones. The purpose of this work was the characterization of neuronal cytoskeletal changes caused by haloperidol in neuroblastoma N1E-115 cells. We also studied the mechanisms by which haloperidol causes cytoskeletal changes. The results showed that haloperidol at 100microM caused a complete cytoskeleton collapse in the majority of the cells. Melatonin, a free radical scavenger, blocks tau hyperphosphorylation, and microtubule disorganization caused by haloperidol in a dose-response mode. Additionally, the indole blocks lipoperoxide formation in haloperidol treated cells. The results indicate that free radicals and tau hyperphosphorylation produced by haloperidol caused a cytoskeletal collapse and the lost of growth cones and neurites. These effects were blocked by melatonin. Data suggest that extrapiramidal symptoms in schizophrenic patients can be produced by cytoskeletal disorganization during adult brain neurodevelopment after prolonged haloperidol treatment that can be prevented by melatonin.

Effect of peripherally administered lipopolysaccharide (LPS) on GTP cyclohydrolase I, tetrahydrobiopterin and norepinephrine in the locus coeruleus in mice

Lipopolysaccharide (LPS), an endotoxin released from the outer membranes of Gram-negative bacteria, triggers cells to synthesize and release inflammatory cytokines that may progress to septic shock in vivo. We found that LPS enhances tetrahydrobiopterin (BH4) biosynthesis by inducing the biosynthetic enzyme GTP cyclohydrolase I (GCH) in vitro in the mouse neuroblastoma cell line N1E-115. Furthermore, we observed that gene expression of GCH in the locus coeruleus (LC) in mice was enhanced by peripheral administration of LPS, resulting in increased concentrations of BH4, and norepinephrine, and its metabolite 4-hydroxy-3-methoxyphenylglycol (MHPG). These results suggest that tyrosine hydroxylase (TH) activity is increased by increased content of BH4 due to enhanced mRNA expression of GCH in the LC resulting in the increase in norepinephrine in the LC during endotoxemia. LPS in blood may act as a stressor to increase norepinephrine biosynthesis in the mouse LC.

Development of resting membrane potentials in differentiating murine neuroblastoma cells (N1E-115) evaluated by flow cytometry

With the aid of a voltage-sensitive oxonol dye, flow cytometry was used to measure relative changes in resting membrane potential (V(m)) and forward angle light scatter (FALS) profiles of a differentiating/differentiated murine neuroblastoma cell line (N1E-115). Electrophysiological differentiation was characterized by V(m) establishment. The (V(m))-time profile was found to be seed cell concentration-dependent for cell densities of less than 2 × 10(4) cells/cm(2). At higher initial cell densities, under differentiating culture conditions, V(m) development commenced on day 2 and reached a steady-state on day 12. The relative distribution of differentiated cells between low and high FALS has been proposed as a potential culture electrophysiological differentiation state index. These experiments offer a general methodology to characterize cultured excitable cells of nervous system origin, with respect to electrophysiological differentiation. This information is valuable in studies employing neuroblastoma cells as in vitro screening models for safety/hazard evaluation and/or risk assessment of therapeutical and industrial chemicals under development.

Release of dopamine and chemoreceptor discharge induced by low pH and high PCO2 stimulation of the cat carotid body

1. Cat carotid bodies were incubated with the precursor [3H]tyrosine to label the catecholamine deposits and then mounted in a superfusion chamber which allowed simultaneous collection of the released [3H]dopamine (DA) and recording of action potentials from the carotid sinus nerve. 2. Low pH (7.2-6.6) superfusion of the carotid bodies for periods of 10 min produced a parallel increase in the release of [3H]DA and chemoreceptor discharge. 3. Carotid sinus nerve denervation of the carotid body 12-15 days prior to the experiments did not modify the release of [3H]DA elicited by low pH. 4. Superfusion of the carotid bodies with Ca(2+)-free, high-Mg2+ (1.6 mM) media reduced basal release of [3H]DA and chemoreceptor discharge by about 30%. Release evoked by low pH was reduced by 82%. Peak and average chemoreceptor discharge recorded in response to low pH were reduced by 28%. 5. Solutions containing weak acids (sodium acetate, 10 mM), adjusted at pH 7.4, elicited release of [3H]DA and increased chemoreceptor discharge. 6. With HCO3-CO2-buffered superfusion media, a reduction of bicarbonate to 5.6 mM (pH 6.8), an increase in CO2 to 20% (pH 6.8), or a simultaneous increase in CO2 to 20% and bicarbonate to 90 mM (pH 7.4), resulted in all cases in a corresponding increase in [3H]DA release and chemoreceptor discharge. The most effective stimulus was 20% CO2-pH 6.8 and the least effective 5% CO2-5.6 mM-HCO3-pH 6.8. 7. Inhibition of carbonic anhydrase with acetazolamide while perfusing the carotid bodies with a 20% CO2-equilibrated (pH 7.4) solution resulted in comparable reductions in the release of [3H]DA and chemoreceptor discharge. 8. It is concluded that the effective acidic stimulus at the carotid body chemoreceptors is an increase in hydrogen ion concentration in type I cells. It is also concluded that DA plays a critical role in the genesis of carotid sinus nerve discharges.

The properties of 5-HT3 receptors in clonal cell lines studied by patch-clamp techniques

1 The characteristics of transmembrane currents evoked by 5-hydroxytryptamine (5-HT) in the neuroblastoma x Chinese hamster brain cell line NCB-20 and neuroblastoma clonal cell line N1E-115 have been studied under voltage-clamp conditions by the whole-cell recording and outside-out membrane patch modes of the patch-clamp technique. 2 In 73% of NCB-20 cells examined (n = 221), and all N1E-115 cells studied (n = 80), 5-HT (10 microM) elicited a transient inward current at negative holding potentials, this being associated with an increase in membrane conductance. In both cell lines responses to 5-HT reversed in sign at a potential of approximately -2 mV and demonstrated inward rectification. 3 The reversal potential of 5-HT-induced currents (E5-HT) recorded from either NCB-20 or N1E-115 cells was unaffected by total replacement of internal K+ by Cs+. In N1E-115 cells, reducing internal K+ concentration from 140 to 20 mM produced a positive shift in E5-HT of approximately 28 mV, whereas reducing external Na+ from 143 to 20 mM was associated with a negative shift in E5-HT of about 37 mV. A large reduction in internal Cl- concentration (from 144 to 6 mM) had little effect on E5-HT. 4 5-HT-induced currents of NCB-20 cells were unaffected by methysergide (1 microM) or ketanserin (1 microM), but were reversibly antagonized by GR38032F (0.1-1.0 nM) with an IC50 of 0.25 nM. GR 38032F (0.3 nM) reduced 5-HT-induced currents in N1E-115 cells to approximately 26% of their control value. 5 On outside-out membrane patches excised from both NCB-20 and N1E-115 cells, 5-HT induced small inward currents which could not be clearly resolved into discrete single channel events. Such responses were: (i) reversibly antagonized by GR 38032F (1 nM) (ii) reversed in sign at 0 mV, and (iii) subject to desensitization. 6 Fluctuation analysis of inward currents evoked by 5-HT (1 microM) in N1E-115 cells suggests that 5-HT gates a channel with a conductance of approximately 310fS. Such a relatively small conductance could readily explain why the response of outside-out membrane patches to 5-HT cannot at present be resolved into clear single channel events.

Kinetics of the membrane current mediated by serotonin 5-HT3 receptors in cultured mouse neuroblastoma cells

1. Ionic currents mediated by serotonin 5-HT3 receptors were studied in the mouse neuroblastoma cell line N1E-115, using suction pipettes for intracellular perfusion and voltage clamp recording. The dependence of the kinetics of the membrane current on serotonin concentration was investigated. 2. At a holding potential of -70 mV application of 5-HT (5-hydroxytryptamine creatinine sulphate) causes a transient inward current. The i-V curve of the peak amplitude is linear between -80 and 60 mV. The reversal potential is 20 +/- 4 mV (mean +/- S.D.). The kinetics of the transient ionic current are independent of the holding potential. 3. In the presence of 5-HT the membrane current decays to a small steady-state level with a single-exponential time course. The time constant of decay decreases with increasing concentration of the agonist, to a minimum value of 6.5 +/- 1.5 s for concentrations of 5-HT greater than or equal to 3 microM. 4. When the agonist is rapidly removed, single-exponential decay of the ionic current is observed. The time constant of this decay in the absence of 5-HT amounts to 6.9 +/- 1.5 s and is independent of the membrane potential and of the concentration of 5-HT used. 5. In the presence of low concentrations of 5-HT the peak amplitude of the inward current evoked with a high concentration of agonist is gradually reduced. The onset of this desensitization follows the same time course as the decay of the membrane current. In the range from 0.7 to 1.5 microM-5-HT both kinetic processes show the same steep concentration dependence. 6. Recovery from desensitization, measured at variable intervals after removal of the agonist, can be fitted by a single-exponential function with a time constant of 18 +/- 4 s. 7. The results show that the kinetic properties of the 5-HT3 receptor-mediated ionic current can only be described by a complex, co-operative model.

Divalent cations modulate 5-HT3 receptor-induced currents in N1E-115 neuroblastoma cells

The influence of extracellular calcium and magnesium ion concentrations upon 5-HT3 receptor-gated membrane currents in murine N1E-115 neuroblastoma cells has been studied under voltage-clamp conditions. A decrease in the concentration of either Ca2+ or Mg2+ from their standard values of 1.0 and 2.0 mM respectively augmented both the amplitude and duration of the 5-HT-induced current, whereas elevating the concentration of either divalent cation produced the opposite effect. Such modulation did not involve a change in the reversal potential of the response.

Pharmacological characterization of serotonin 5-HT3 receptor-mediated electrical response in cultured mouse neuroblastoma cells

The aim of this study was to investigate the pharmacological characteristics of the 5-hydroxytryptamine-(5-HT)-induced electrical response in cultured neuroblastoma N1E-115 cells of the mouse. In these cells 5-HT induces a transient membrane depolarization, which is associated with a transient inward current, that has been recorded in voltage clamp experiments on whole cells. The peak amplitude of the inward current depends on the concentration of 5-HT applied. Maximum peak inward current was evoked by 10 microM 5-HT and half maximum effect by 2 microM. Responses to 5-HT were blocked by nanomolar concentrations of selective 5-HT3-receptor antagonists, whereas the selective agonist 2-methyl-5-HT mimicked the membrane depolarization induced by 5-HT. A number of agonists and antagonists, which are known to act on 5-HT1-like, 5-HT2, dopaminergic and adrenergic receptors failed to affect the response to 5-HT in neuroblastoma cells. Observed antagonistic effects of SCH 23390 [(R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepi n-7-ol hemimaleate] and haloperidol are discussed. The inhibitory effect of the 5-HT3 receptor antagonist, ICS 205-930 [(3 alpha-tropanyl)-1H-indole-3-carboxylic acid ester] has been demonstrated. When cells were exposed to 0.1 nM ICS 205-930 the maximum evoked response was reduced by about 50%, but a surmountable shift of the concentration-response curve of 5-HT was not observed. The kinetics of the 5-HT-induced inward current remained unchanged in the presence of ICS 205-930. Recovery from the block by ICS 205-930 was very slow.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclic nucleotide potentiation of muscarinic responses in neuroblastoma cells

The role of cyclic nucleotides in modulating acetylcholine-induced and dopamine-induced responses was examined with cultured neuroblastoma N1E-115 cells by means of intracellular recording techniques. Acetylcholine-induced muscarinic hyperpolarization and muscarinic depolarization were potentiated by bath application of a dibutyryl analog of adenosine 3',5'-phosphate (cyclic AMP) or phosphodiesterase inhibitors, 3-isobutyl-1-methylxanthine and 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone. Dibutyryl cyclic AMP did not affect the resting membrane potential and membrane resistance. Acetylcholine-induced nicotinic depolarization was unaffected by dibutyryl cyclic AMP or phosphodiesterase inhibitors. Intracellular pressure injection of cyclic AMP caused a potentiation of muscarinic hyperpolarization and muscarinic depolarization without marked change in the resting membrane potential. Nicotinic depolarization and dopamine depolarization were not affected by cyclic AMP injection. Among the possible metabolites of cyclic AMP, injection of adenosine potentiated muscarinic hyperpolarization, but did not change nicotinic depolarization and dopamine depolarization. Injection of guanosine 3',5'-phosphate (cyclic GMP) potentiated muscarinic hyperpolarization and muscarinic depolarization without effect on nicotinic depolarization and dopamine depolarization. We conclude that cyclic AMP and cyclic GMP enhance muscarinic responses in neuroblastoma cells. It is suggested that synaptic transmission in the nervous system may be modulated postsynaptically by changes in intracellular cyclic nucleotide levels.

Acetylcholine-activated currents in mouse neuroblastoma cells

The nicotine and muscarinic responses of differentiated mouse neuroblastoma cells from the clonal line N1E 115 to applied cholinergic agents were recorded using single channel and whole cell patch clamp techniques. An inward macroscopic current induced by acetylcholine (ACh) at the resting potential was blocked by curare; cell-attached recordings revealed a single channel conductance of 18 pS and a lifetime of 36 ms at 30 degrees C, with 200 nM ACh. The zero current potential was close to 0 mV. The kinetics of these nicotinic currents were described by multiexponential functions for both the open and closed time distributions. An outward single channel current, present at resting and slightly depolarized potentials, was also observed and has been tentatively described as being dependent on muscarinic receptor activation, as it was usually blocked by atropine. Under our conditions of whole cell clamp, no macroscopic outward current sensitive to ACh was observed.

The dopamine response in mouse neuroblastoma cells is mediated by serotonin 5HT3 receptors

Serotonin (5HT) and dopamine (DA) induce, in neuroblastoma N1E-115 cells, a transient membrane depolarization associated with an inward current. The half-maximum response is obtained with 2 microM 5HT or 200 microM DA. The maximum response to 5HT is 2-3 times that to DA. The selective 5HT3 receptor antagonists ICS 205-930 and MDL 72222 at nanomolar concentrations block both the 5HT- and the DA-induced response. High concentrations (10 microM) of 5HT2 receptor antagonists are without effect. It is concluded that, in N1E-115 cells, 5HT and DA activate a single population of 5HT3 receptors.

Cyclic AMP-mediated potentiation of muscarinic hyperpolarization in neuroblastoma cells

Adenosine, 2-chloroadenosine and prostaglandin E1 which are known to increase cyclic AMP in neuroblastoma cells potentiated the acetylcholine-induced muscarinic hyperpolarization of the cells without changing the resting membrane potential. The potentiation caused by 2-chloroadenosine was further augmented by Ro 20-1724, a phosphodiesterase inhibitor. A direct intracellular pressure application of cyclic AMP potentiated the muscarinic hyperpolarization without changing the resting membrane potential. Morphine which inhibits adenylate cyclase antagonized 2-chloroadenosine-induced potentiation of the muscarinic hyperpolarization. These results suggest that changes in cyclic AMP level modulate the muscarinic response of neuroblastoma cells.