OBJECTIVETo investigate the effects of ropivacaine on Gamma-aminobutyric acid(GABA)-activated currents in dorsal root ganglion (DRG) neurons in rats and discuss the analgesia mechanism of ropivacaine.

METHODSBy means of using whole-cell patch-clamp technique, to investigate the modulatory effects of ropivacaine on GABA-activated currents (I(GABA)) in acutely isolated dorsal root ganglion neurons.

RESULTS(1) In 48 out of 73DRG cells (65.7%, 48/73), to perfusion ropivacaine bromide (0.1 - 1 000 micromol/L) were sensitive. Which produce in 0 to 380 pA current. (2) The majority of the neurons examined (74.5%, 73/98) were sensitive to GABA. Concentration of 1 - 1 000 micromol/L GABA could activate a concentration-dependent inward current, which manifested obvious desensitization, and the inward currents could be blocked byGABA-receptor selective antagonist of bicuculline (100 micromol/L). (3) After the neurons were treated with ropivacaine (0.1 - 1000 micromol/L) prior to the application of GABA (100 micromol/L) 30 s, GABA currents were obviously increased. Ropivacaine could make dose-response curve of the GABA up, EC50 is 23.46 micromol/L. Ropivacaine shifted the GABA dose-response curve upward and increased the maximum response to the contrast about 153%.

CONCLUSIONThe enhancement of ropivacaine to DRG neurons activation of GABA current, can lead to enhancement of pre-synaptic inhibition at the spinal cord level. This may be one of the reasons for the anesthetic effect and analgesia for ropivacaine in epidural anesthesia.

Amides ; pharmacology ; Animals ; Ganglia, Spinal ; cytology ; physiology ; Membrane Potentials ; drug effects ; Neurons ; cytology ; drug effects ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA-A ; physiology

AIMThe effects of morphine on the potassium ionic currents of caudate nucleus neurons of neonatal rat were studied.

METHODSUsing of whole cell voltage clamp technique on caudate nucleus neurons, applied morphine chronically or acutely on it. In order to research the effects of morphine for voltage-gated of potassium ionic currents.

RESULTSThe amplitude of potassium ionic currents are increased by applied morphine acutely in caudate nucleus from (2.6 +/- 0.4) nA to (3.3 +/- 0.5) Na, naloxone can block the effect of morphine on K+ current and the currents are decreased to (2.4 +/- 0.4) nA. If applied morphine in caudate nucleus chronically, the amplitude of potassium ionic currents are increased from (2.6 +/- 0.4) nA to (3.1 +/- 0. 5) nA. After applied naloxone, the currents are decreased to (2.4 +/- 0.4) nA.

CONCLUSIONThe effects of morphine increased potassium ionic currents by micro-opioid receptor mediated and induced the hyper polarization of neurons, leading to inhibition of neural activity.

Animals ; Caudate Nucleus ; cytology ; drug effects ; physiology ; Morphine ; pharmacology ; Neurons ; drug effects ; physiology ; Patch-Clamp Techniques ; Potassium Channels ; drug effects ; physiology ; Rats ; Rats, Wistar

OBJECTIVETo set up a platform for phenotype-based primary screening of drug candidates promoting neuronal subtype differentiation in embryonic stem cells (ES) with light microscope.

METHODSHanging drop culture 4-/4+ method was employed to harvest the cells around embryoid body (EB) at differentiation endpoint. Morphological evaluation for neuron-like cells was performed with light microscope. Axons for more than three times of the length of the cell body were considered as neuron-like cells. The compound(s) that promote neuron-like cells was further evaluated. Icariin (ICA, 10(-6)mol/L) and Isobavachin (IBA, 10(-7)mol/L) were selected to screen the differentiation-promoting activity on ES cells. Immunofluorescence staining with specific antibodies (ChAT, GABA) was used to evaluate the neuron subtypes.

RESULTSThe cells treated with IBA showed neuron-like phenotype, but the cells treated with ICA did not exhibit the morphological changes. ES cells treated with IBA was further confirmed to be cholinergic and GABAergic neurons.

CONCLUSIONPhenotypic screening with light microscope for molecules promoting neuronal differentiation is an effective method with advantages of less labor and material consuming and time saving, and false-positive results derived from immunofluorescence can be avoided. The method confirms that IBA is able to facilitate ES cells differentiating into neuronal cells, including cholinergic neurons and GABAergic neurons.

Animals ; Cell Differentiation ; drug effects ; physiology ; Cell Line ; Drug Evaluation, Preclinical ; methods ; Embryoid Bodies ; cytology ; Embryonic Stem Cells ; cytology ; Mice ; Nerve Regeneration ; drug effects ; Neurons ; cytology ; Phenotype

OBJECTIVETo explore the electrophysiological properties of differentiation of rat bone marrow-derived stromal stem cells (rBMSCs) to neuron-like cells in vitro by edaravone, a new type of free radical scavenger.

METHODSStromal stem cells were separated from rat bone marrow with Ficoll-Paque reagent and expanded in different culture medium in vitro. rBMSCs were induced by edaravone containing serum-free L-DMEM. Morphologic observation and Western blot analysis including the expression of Nav1.6, Kv1.2, Kv1.3, Cav1.2 were performed, and whole patch-clamp technique was used.

RESULTSCyton contraction and long processes were shown in differentiated stromal stem cells. Nav1.6, Kv1.2, Kv1.3 and Cav1.2 were expressed in both differentiated and undifferentiated cells. However, the expression of channel proteins in differentiated cells was up-regulated. Consistently, their resting potential and outward currents were also enhanced in the differentiated cells, which was especially significant in the outward rectifier potassium current.

CONCLUSIONIn vitro, neuron-like cells derived from rBMSCs, induced by edaravone, possess electrophysiological properties of neurons.

Animals ; Antipyrine ; analogs & derivatives ; pharmacology ; Blotting, Western ; Bone Marrow Cells ; cytology ; physiology ; Cell Differentiation ; drug effects ; Male ; Neurons ; cytology ; physiology ; Rats ; Rats, Sprague-Dawley ; Stromal Cells ; cytology ; physiology

Animals ; Habenula ; cytology ; drug effects ; Male ; Microelectrodes ; Neurons ; drug effects ; physiology ; Pain ; Pregnanolone ; pharmacology ; Rats ; Rats, Wistar

Neuronal PC12 cells induced by nerve growth factor (NGF) have been considered to be postmitotic and lack the ability to divide. However, in this study, we not only detected DNA synthesis but also observed cell division in some morphologically differentiated neuronal PC12 cells bearing long neurites. More interestingly, in addition to the division of perikaryon, the neurites located on the division site of the cell membrane also divided into two parts and were allocated to the two daughter cells. These results demonstrate that the morphologically differentiated neuronal PC12 cells still retain the ability to divide. This is the first report that neuronal PC12 cells as well as their neurites can divide.
Animals ; Cell Differentiation ; drug effects ; Cell Division ; drug effects ; DNA Replication ; drug effects ; physiology ; Nerve Growth Factor ; pharmacology ; Neurites ; drug effects ; Neurons ; cytology ; PC12 Cells ; Rats

The effects of magnesium sulfate (MgSO4) on sodium currents (Na(+) currents) were studied in freshly dissociated hippocampal CA(1) neurons of rat using the whole-cell patch-clamp technique. The results indicated that MgSO4 caused a concentration-dependent and voltage-dependent decrease in Na(+) currents. The half-inhibitory concentration (IC(50)) was 4.05 mmol/L. This action was frequency-independent. The results also showed that 4 mmol/L MgSO4 shifted the steady state activation curve of Na(+) currents towards positive potential (control V(h)=-55.8+/-6.8 mV, MgSO4 V(h)=-34.2+/-6.2 mV, n=8, P<0.01) without changing the slope factor. However, the steady state inactivation curve was not affected. These results suggest that blockade of Na(+) currents by MgSO4 might be an interpretation for its neuroprotection against damages induced by ischemia and oxygen deprivation.
Animals ; Hippocampus ; cytology ; drug effects ; physiology ; Magnesium Sulfate ; pharmacology ; Neurons ; drug effects ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Wistar ; Sodium Channel Blockers ; pharmacology ; Sodium Channels ; physiology

OBJECTIVETo study the effects of pentobarbital sodium in generation and modulation of rhythmical respiration in neonatal rats.

METHODSThe effects of pentobarbital sodium were examined on hypoglossal nerve (XII) rootlets and inspiratory neurons in the medullary preparations including the medial region of the nucleus retrofacialis, pre-Bötzinger complex and the dorsal respiratory group of neonatal rats aged 0-3 days. The electrical activity of XII nerve rootlets and inspiratory neurons were recorded. Different doses of pentobarbital sodium (20, 40, 60, 80 micromol/L) were added into modified Krebs solution to observe changes in the discharge activity of XII nerve and inspiratory neurons. Bicuculline was used to further investigate the mechanisms that pentobarbital sodium suppresses respiration.

RESULTSThe discharge activity inhibition of XII nerve was increased as pentobarbital sodium doses increased from 20 to 60 micromol/L, but no significant difference was observed between the doses of 60 and 80 micromol/L. Bicuculline can partly restore the rhythmical respiration discharge activity.

CONCLUSIONPentobarbital sodium can suppress respiration partly via GABAA receptors.

Adjuvants, Anesthesia ; pharmacology ; Animals ; Animals, Newborn ; Dose-Response Relationship, Drug ; Medulla Oblongata ; cytology ; drug effects ; physiology ; Neurons ; drug effects ; physiology ; Pentobarbital ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA-A ; physiology ; Respiration ; drug effects ; Respiratory Center ; drug effects ; physiology

Many extracellular matrix molecules are expressed in the embryonic nervous system and there is some evidence that they are important regulators of neural development. Of these molecules, laminin appears to be the most potent, affecting virtually all neurons of the peripheral and central nervous system. This study was undertaken to investigate the effects of laminin on the proliferation and differentiation of cultured neuroepithelial cells taken from fetal rat forebrains (embryonic day 17-19). The results are summarized as follows. 1) Neuroepithelial cells cultivated in epidermal growth factors containing serum-free medium subsequently differentiated into neurons, astrocytes, and oligodendrocytes. 2) Neuronal cells derived from neuroepithelial cells were immunoreactive for gamma-aminobutyric acid (GABA) or substance P, but were not for serotonin and tyrosine hydroxylase. 3) In western blot analysis, the phosphorylated neurofilament content in neuronal cells was higher in culture on laminin than in culture on poly-L-lysine (PLL). 4) The proliferation rate of GABAergic neurons was higher in culture on laminin than in culture on PLL. These results suggest that GABAergic and substance P-ergic neurons can be differentiated from neuroepithelial cells and that laminin promotes the differentiation of neuronal cells from neuroepithelial cells and the increased proliferation rate of GABAergic cells.
Animal ; Brain/drug effects* ; Brain/cytology ; Cell Aging/drug effects ; Cell Differentiation/drug effects ; Cell Division/drug effects ; Cells, Cultured ; Epidermal Growth Factor/pharmacology* ; Epithelial Cells/drug effects ; Epithelial Cells/cytology ; GABA/physiology ; Laminin/pharmacology* ; Neurons/physiology ; Neurons/drug effects* ; Neurons/cytology* ; Rats/embryology

Panax notoginseng saponins (PNS) are very important extracts from roots of medicinal herb Sanchi Ginseng which is highly regarded in China for its therapeutic ability to meliorate blood-circulation, anti-anoxia, improve memory, and anti-caducity effects. In this study, we used blind whole-cell voltage-clamp recordings to detect the effects of PNS on long-term potentiation (LTP) in the CA1 region of the hippocampus, and investigated the electrophysiological mechanisms underlying potentiating effects of PNS on learning and memory. Wistar rats (3-4 weeks) were decapitated and hippocampal slices (400 microm thick) were cut coronally. Excitatory postsynaptic currents (EPSCs) were recorded by patch clamp technique in whole-cell configuration. The Schaffer collateral/commissural pathway was stimulated by high frequency stimulation (HFS: 100 Hz) pulses to induce LTP. The findings showed that 0.1 - 0.4 g x L(-1) PNS significantly depressed the amplitude of EPSCs (P < 0.05) and had no facilitative effects on LTP of pyramidal neurons located in the CA1 region. PNS in the concentrations of 0.04 - 0.05 g x L(-1) did not appreciably affect the amplitude of EPSCs (P > 0.05) but markedly increased the amplitude of LTP (P < 0.05). In conclusion, 0.04 - 0.05 g x L(-1) PNS could facilitate LTP in the CA1 region of the rat hippocampus and it is reasonable to suggest that this action may contribute to its potentiating effects on learning and memory.
Animals ; Excitatory Postsynaptic Potentials ; drug effects ; Ginsenosides ; isolation & purification ; pharmacology ; Hippocampus ; drug effects ; physiology ; Long-Term Potentiation ; drug effects ; Neurons ; drug effects ; physiology ; Panax notoginseng ; chemistry ; Pyramidal Cells ; cytology ; drug effects ; physiology ; Rats ; Rats, Wistar