We have previously reported that the spontaneous release of [3H]5-hydroxytryptamine(5-HT) was markedly decreased by hypoxic insult in rat hippocampal slices. In the present study, the effect of glucose on 5-HT release was examined. Fractional release of [3H]5-HT was measured from an incubation medium exchanged every 10 min for 140 min and after stabilization of [3H]5-HT release, 10 or 20 min period of hypoxia was induced by exchanging the media which have been previously saturated by 95% N2/5% CO2 gas. In the media containing 1, 2, 5, 10 or 20 mM glucose, [3H]5-HT release was stabilized after 40 min of incubation. Exposure to hypoxia decreased [3H]5-HT release up to 60% of the control level in a glucose concentration-dependent manner and recovered gradually after hypoxic periods. However, in the media containing no glucose, the spontaneous release of [3H] 5-HT increased continuously during incubation. Moreover, when hippocampal slices were exposed to hypoxia, the [3H]5-HT release increased up to 150% of the control level and recovered gradually to the control level after hypoxic periods. These results demonstrate that hypoxia inhibits or enhances 5-HT release in the presence or absence of extracellular glucose respectively and suggest that the availability of extracellular glucose is a key factor to determine the direction of 5-HT release under hypoxic condition.
Animal ; Cell Hypoxia ; Dose-Response Relationship, Drug ; Glucose/*pharmacology ; Hippocampus/*secretion ; In Vitro ; Male ; Rats ; Rats, Sprague-Dawley ; Serotonin/*secretion

OBJECTIVETo observe the dynamics of hippocampal release of glutamate (Glu) and gamma-aminobutyric acid (GABA) in epilepsy (TLE) after administration with high frequency stimulation (HFS).

METHODSThe SD were divided into four groups (n =10): (1) Control group (KB) the rats were injected intraperitoneally with saline 0.9%. (2) Kainic acid (KA) group: the rats were injected with KA. (3) Pseudo-deep brain stimulation (DBS) group: the KA-induced rats were implanted with rheophores alone. (4) DBS group: KA induced-rats with DBS in hippocampal epileptic foci. We then collected hippocampal extracellular fluid by microdialysis and the levels of Glu and GABA were measured by high-performance liquid chromatography (HPLC) and fluorescence detection.

RESULTSThere was no difference in the baseline of Glu and GABA in the four groups. In contrast, a significant increase in the content of Glu and GABA was shown in the three periods of KA-kindled seizures. Electrical stimulation of hippocampus resulted in a decrease of hippocampal Glu contents, while there was no change in GABA contents. Additionally, HFS of hippocampus normalized the Glu/GABA ratio in the chronic period of seizures.

CONCLUSIONThe high frequency stimulation of epileptic foci may protect against seizures by modulating the extracellular release of hippocampal Glu.

Animals ; Electric Stimulation ; methods ; Epilepsy ; chemically induced ; therapy ; Glutamic Acid ; secretion ; Hippocampus ; metabolism ; Kainic Acid ; Kindling, Neurologic ; drug effects ; Male ; Rats ; Rats, Sprague-Dawley ; gamma-Aminobutyric Acid ; secretion

AIMTo determine whether serotonin, a major neurotransmitter in brain, can modulate the production of secretory beta-amyloid protein precursor (sAPP) by activation of serotonin 5-HT2C receptor.

METHODSThe hippocampal slices of rats were incubated with various concentrations of serotonin, M-110, or L-107. sAPP released into the incubation medium were assayed by Western blot analysis assay with monoclonal antibody 22C11 for 2 h.

RESULTSVarious concentrations of serotonin (1.0 x 10(-2) - 1.0 x 10(3) micromol x L(-1)), M-110, a serotonin 5-HT2C agonist (1.5 x 10(-6) - 1.5 x 10(3) micromol x L(-1)), showed positive effect on the production of sAPP while L-107, a serotonin 5-HT2C antagonist (1.0 x 10(-9) - 1.0 x 10(3) micromol x L(-1)), showed negative effect on the production of sAPP over controls.

CONCLUSIONSerotonin modulates production of secretory amyloid beta-protein precursor through serotonin 5-HT2C receptor in incubated rat hippocampal slices.

Amyloid beta-Protein Precursor ; secretion ; Animals ; Hippocampus ; metabolism ; In Vitro Techniques ; Male ; Peptide Fragments ; secretion ; Rats ; Rats, Sprague-Dawley ; Receptor, Serotonin, 5-HT2C ; Serotonin ; pharmacology ; Serotonin 5-HT2 Receptor Agonists ; Serotonin 5-HT2 Receptor Antagonists

Animals ; Animals, Newborn ; Cell Hypoxia ; Cell Survival ; drug effects ; Female ; Hippocampus ; cytology ; drug effects ; L-Lactate Dehydrogenase ; secretion ; Male ; Malondialdehyde ; analysis ; Neuroprotective Agents ; pharmacology ; Propofol ; pharmacology ; Rats ; Rats, Wistar ; Superoxide Dismutase ; metabolism

OBJECTIVETo elucidate the inhibitory effects of recombinant Chinese scorpion neurotoxin BmK IM on seizures induced by pentylenetetrazol (PTZ) and the possible mechanism.

METHODSAfter purifying recombinant BmK IM from an E. coli cell line, its toxicity (both LD50 and minimum lethal dose) on rats was determined. BmK IM was then microinjected into the CA3 region of the right hippocampus and its ability to inhibit the effects of an intraperitoneal injection of PTZ was assessed. The effects of BmK IM on the electrophysiological properties of isolated CA3 pyramidal neurons were then studied using whole-cell patch clamp techniques.

RESULTSBmK IM can significantly prolong the latent period of epileptic seizures, decrease the degree of seizures, and decrease the frequency of epileptiform discharges induced by PTZ. At the same time, 24h after injection of BmK IM into the hippocampal tissue, BmK IM significantly reduces the concentration of the neurotransmitter glutamate and alleviates PTZ-induced lesions in the hippocampus. Whole-cell patch clamp recordings indicate that BmK IM inhibits INa of rat hippocampal neurons in a dose-dependent manner. BmK IM significantly shifts the activation curve of INa in a positive direction, indicating that BmK IM enhances the threshold potential of INa.

CONCLUSIONSBmK IM has significant anti-epileptic properties, and may prove useful as a drug in the therapy of epilepsy. The inhibitory effects of BmK IM on seizures caused by pentylenetetrazol might depend on reductions in the release of presynaptic glutamate via the blocking of Na+ channels.

Animals ; Glutamine ; secretion ; Hippocampus ; drug effects ; Male ; Microinjections ; Pentylenetetrazole ; Peptides ; administration & dosage ; therapeutic use ; Rats ; Rats, Sprague-Dawley ; Recombinant Proteins ; administration & dosage ; therapeutic use ; Scorpion Venoms ; administration & dosage ; therapeutic use ; Seizures ; chemically induced ; prevention & control ; Sodium Channels ; drug effects

OBJECTIVETo investigate the effect of extracellular regulating kinase (ERK) signaling pathway on the secretion of gamma-aminobutyric acid (GABA) in cultured rat hippocampal neurons induced by stromal cell derived factor-1 (SDF-1).

METHODSThe hippocampal neurons of newborn SD rats were cultured and identified in vitro; the phosphorylation level of ERK1/2 was examined by Western blot; ELISA was used to detect the effect of PD98059, a ERK1/2 specific blocker on GABA secretion of cultured hippocampal neurons and Western blot were adopted to measure the protein expression levels of glutamate decarboxylase (GAD65/67) and gamma aminobutyric acid transporter (GAT); after blocking ERK1/2 signaling pathway with PD98059; RT-PCR was used to detect the mRNA expression levels of GAT-1 and GAD65 after treated with PD98059.

RESULTSThe levels of ERKl/2 phosphorylation were increased significantly by SDF1 acting on hippocampal neurons, and CX-CR4 receptor blocker AMD3100, could inhibit SDF-1 induced ERK1/2 activation; SDF-1 could inhibit the secretion of GABA in cultured hippocampal neurons, and ERK1/2 specific inhibitor PD98059, could partly reverse the inhibition of GABA secretion by SDF-1. The effects of SDF-1 on cultured hippocampal neurons was to decrease the mRNA genesis of glutamic acid decarboxylase GAD65 and GABA transporter GAT-1, besides, ERK inhibitor PD98059 could effectively flip the effect of SDF-1. The results of Western blot showed that SDF-1 could inhibit the protein expression of GAT-1 and GAD65/67 in hippocampal neurons and the inhibition of GAT-1 and GAD65/67 protein expression could be partially restored by ERK1/2 blocker.

CONCLUSIONSDF-1 acts on the CXCR4 of hippocampal neurons in vitro, and inhibits the expression of GAD by activating the ERK1/2 signaling pathway, and this may represent one possible pathway of GABA secretion inhibition.

Animals ; Blotting, Western ; Cells, Cultured ; Chemokine CXCL12 ; pharmacology ; Flavonoids ; pharmacology ; Glutamate Decarboxylase ; metabolism ; Hippocampus ; cytology ; MAP Kinase Signaling System ; Neurons ; metabolism ; Phosphorylation ; RNA, Messenger ; Rats ; Rats, Sprague-Dawley ; Receptors, CXCR4 ; metabolism ; gamma-Aminobutyric Acid ; secretion

OBJECTIVETo study the effect of ginsenoside Rb1 on GSKbeta/IDE signal transduction pathway and Abeta protein secretion in hippocampal neurons of high glucose-treated rats.

METHODHippocampal neurons of 24 h-old newly born SD rats were primarily cultured, inoculated in culture medium under different conditions, and then divided into the normal group, the high glucose group, the LiCl group and the Rb1 group. After being cultured for 72 h, the expressions of their phosphorylated GSK3beta, total GSK3beta and IDE protein were detected by Western blotting analysis. The mRNA expressions of GSK3beta and IDE were determined by RT-PCR. The ELISA assay was used to detect the secretion of Abeta protein in cell supernatant.

RESULTCompared with the normal group, the high glucose group showed increase in the p/tGSK3beta protein ratio and the secretion of Abeta protein and decrease in IDE protein and mRNA (P < 0.05). Compared with the high glucose group, both Rb1 and LiCl groups showed decrease in the p/tGSK3beta protein ratio and the expression of Abeta protein and increase in IDE protein and mRNA expression (P < 0.05). Compared with the LiCl group, the Rb1 group showed no significant difference in the expressions of p/tGSK3beta protein, IDE protein, mRNA and Abeta protein expression. In addition, the GSK3beta mRNA expression of the four groups had no significant difference.

CONCLUSIONGinsenoside Rb1 may reduce the secretion of Abeta protein in hippocampal neurons by reducing the phosphorylation of GSK3beta, down-regulating the ratio of pGSK3beta/GSK3beta and upregulating the expression of IDE.

Amyloid beta-Peptides ; genetics ; metabolism ; secretion ; Animals ; Dietary Carbohydrates ; adverse effects ; Gene Expression Regulation ; drug effects ; Ginsenosides ; pharmacology ; Glucose ; adverse effects ; Glycogen Synthase Kinase 3 ; genetics ; metabolism ; Glycogen Synthase Kinase 3 beta ; Hippocampus ; cytology ; Insulin ; metabolism ; Insulysin ; genetics ; metabolism ; Neurons ; cytology ; drug effects ; metabolism ; secretion ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; drug effects