AIMTo study changes of function of transmitter glycine in nitrogen narcosis.

METHODSSynaptosomes of rat spinal cord were prepared. Glycine uptake of synaptosomes of rat spinal cord in 0.7 MPa (7ATA) hyperbaric air pressure was observed by the methods of isotope.

RESULTSGlycine uptake slowed down and took a longer period of time to reach saturation in 0.7 MPa (7ATA). The maximum glycine uptake was lessened. Vm was diminished, but Km was increased. Vm rose in 0.7 MPa (7ATA) when corticosterone was added.

CONCLUSIONWhen nitrogen narcosis arose in 0.7 MPa (7ATA), the function of transporters of glycine re-uptake was reduced, the affinity of glycine for transporters subsided. Corticosterone was conductive to the recovery of the function of glycine transporters of high affinity.

Air Pressure ; Animals ; Glycine ; metabolism ; Rats ; Rats, Sprague-Dawley ; Spinal Cord ; metabolism ; Synaptosomes ; metabolism

To investigate the effect of thiopental sodium on the release of glutamate and gamma-aminobutyric acid (GABA) from synaptosomes in the prefrontal cortex, synaptosomes were made, the spontaneous release and the evoked release by 30 mmol/L KCl or 20 micromol/L veratridine of glutamate and GABA were performed under various concentrations of thiopental sodium (10-300 micromol/L), glutamate and GABA concentrations were determined by reversed-phase high-performance liquid chromatography. Our results showed that spontaneous release and evoked release of glutamate were significantly inhibited by 30 micromol/L, 100 micromol/L and 300 micromol/L thiopental sodium, IC50 of thiopental sodium was 25.8 +/- 2.3 micromol/L for the spontaneous release, 23.4 +/- 2.4 micromol/L for KCl-evoked release, and 24.3 +/- 1.8 micromol/L for veratridine-evoked release. But GABA spontaneous release and evoked release were unaffected. The study showed that thiopental sodium with clinically related concentrations could inhibit the release of glutamate, but had no effect on the release of GABA from rats prefrontal cortical synaptosomes.
Glutamic Acid/*metabolism ; Hypnotics and Sedatives/pharmacology ; Prefrontal Cortex/*metabolism ; Rats, Sprague-Dawley ; Synaptosomes/*metabolism ; Thiopental/*pharmacology ; gamma-Aminobutyric Acid/*metabolism

RalA GTPase, a member of Ras superfamily proteins, shows alternative forms between the active GTP-binding and the inactive GDP-binding states. Ral-specific guanine nucleotide exchange factor such as RalGDS interacts with activated Ras and cooperates with Ras indicating that Ral can be activated through Ras signaling pathway. Another activation path for Ral are through Ca2+-dependent but Ras-independent manner. In this study, studies were carried out to examine possible effects of Ca2+ and calmodulin, Ca2+-binding protein, directly on the GTP/GDP-binding state to recombinant unprenylated GST-RalA proteins. The results showed that Ca2+ stimulated the binding of GTP to RalA, whereas it reduced the binding of GDP to RalA. However, it does not involve a high affinity association of Ca2+ with RalA. Ca2+/calmodulin stimulated the GTPase activity of RalA. These results indicate that Ca2+ alone activates RalA by stimulating GTP-binding to RalA and Ca2+/calmodulin inactivates RalA by increasing the activity of RalGTPase.
Animal ; Brain/metabolism ; Calcium/*metabolism ; Calmodulin/*metabolism ; GTP Phosphohydrolases/*metabolism ; Guanosine Diphosphate/metabolism ; Guanosine Triphosphate/*metabolism ; Rats ; Support, Non-U.S. Gov't ; Synaptosomes/metabolism

AIMTo study the effects of sodium magnesium fructose diphosphate (SMFD) on free calcium concentration and nitric oxide synthase activity of ischemic synaptosome, so as to explore the protective mechanisms of SMFD on cerebral ischemia.

METHODSThe synaptosomes from normal rat brain were prepared by phase partition and cultured with oxygen-glucose deprivation to establish ischemic synaptosome model. The intrasynaptosomal free calcium concentration and nitric oxide synthase activity were detected separately after the synaptosomes were co-incubated with SMFD (1.3 mmol.L-1) or fructose-1, 6-diphosphate (FDP, 4.0 mmol.L-1) for 60 min.

RESULTSSMFD decreased the free calcium concentration and reduced the activity of nitric oxide synthase (NOS) of ischemic synaptosomes. Its effects were more powerful than those of FDP.

CONCLUSIONSMFD may protect neurons from ischemic injury by preventing intracellular Ca2+ overload and inhibiting the activity of nitric oxide synthase.

Animals ; Brain Ischemia ; enzymology ; metabolism ; Calcium ; metabolism ; Chelating Agents ; pharmacology ; Fructosediphosphates ; pharmacology ; Magnesium ; chemistry ; Male ; Nitric Oxide Synthase ; drug effects ; metabolism ; Rats ; Rats, Wistar ; Sodium ; chemistry ; Synaptosomes ; metabolism

To investigate the effect of thiopental sodium on the release of glutamate and gamma-aminobutyric acid (GABA) from synaptosomes in the prefrontal cortex, synaptosomes were made, the spontaneous release and the evoked release by 30 mmol/L KCl or 20 micromol/L veratridine of glutamate and GABA were performed under various concentrations of thiopental sodium (10-300 micromol/L), glutamate and GABA concentrations were determined by reversed-phase high-performance liquid chromatography. Our results showed that spontaneous release and evoked release of glutamate were significantly inhibited by 30 micromol/L, 100 micromol/L and 300 micromol/L thiopental sodium, IC50 of thiopental sodium was 25.8 +/- 2.3 micromol/L for the spontaneous release, 23.4 +/- 2.4 micromol/L for KCl-evoked release, and 24.3 +/- 1.8 micromol/L for veratridine-evoked release. But GABA spontaneous release and evoked release were unaffected. The study showed that thiopental sodium with clinically related concentrations could inhibit the release of glutamate, but had no effect on the release of GABA from rats prefrontal cortical synaptosomes.
Animals ; Glutamic Acid ; metabolism ; Hypnotics and Sedatives ; pharmacology ; Male ; Prefrontal Cortex ; metabolism ; Rats ; Rats, Sprague-Dawley ; Synaptosomes ; metabolism ; Thiopental ; pharmacology ; gamma-Aminobutyric Acid ; metabolism

OBJECTIVETo investigate the effect of microwave radiation on synaptic structure, characteristic of synaptosome, the contents and release of neurotransmitters in hippocampus in Wistar rats.

METHODSWistar rats were exposed to microwave radiation with average power density of 30 mW/cm(2). Electron telescope was used to study the change of the synaptic structure at 6 h after radiation and to identify synaptosome. Flow cytometry and electron spin resonance were used to study the change of the concentration of Ca(2+) in synapse and the fluidity of membrane proteins of synaptosome. High performance liquid chromatography (HPLC) and spectrophotometer were used to study the changes of contents and release of amino acids and acetylcholine in hippocampus.

RESULTSMicrowave radiation of 30 mW/cm(2) caused deposits of synapse vesicle, elongation of active zone, the increase of thickness of postsynaptic density (PSD) and curvature, and perforation of synapse. The concentration of Ca(2+) in synapse (P<0.01) and tc of membrane proteins (P<0.01) of synaptosome increased contents of glutamic acid and glycine (P<0.01) and release of GABA increased the increase of contents and release of acetylcholine, and activity of acetyl cholinesterase (P<0.01) increased.

CONCLUSIONMicrowave radiation can induce the injure of synaptic structure and function of hippocampus, and then induce the disorder of the ability of learning and memory in rats.

Animals ; Hippocampus ; metabolism ; pathology ; radiation effects ; Male ; Microwaves ; adverse effects ; Rats ; Rats, Wistar ; Synapses ; metabolism ; pathology ; radiation effects ; Synaptosomes ; metabolism ; radiation effects

To investigate the effect of propofol on the release of glutamate and gamma-aminobutyric acid (GABA) from rat hippocampal synatosomes, synaptosomes was made from hippocampus and incubated with artificial cerebrospinal fluid (aCSF). With the experiment of Ca(2+)-dependent release of glutamate and GABA, dihydrokainic acid (DHK) and nipectic acid were added into aCSF. For the observation of Ca(2+)-independent release of glutamate and GABA, no DHK, nipectic acid and Ca2+ were added from aCSF. The release of glutamate and GABA were evoked by 20 micromol/L veratridine or 30 mmol/L KCI. The concentration of glutamate and GABA in aCSF was measured by using high-performance liquid chromatography (HPLC). 30, 100 and 300 micromol/L propofol significantly inhibited veratridine-evoked Ca(2+)-dependent release of glutamate and GABA (P < 0.01 or P < 0. 05). However, propofol showed no effect on elevated KCl-evoked Ca(2+)-dependent release of glutamate and GABA (P > 0.05). Veratridine or elevated KCI evoked Ca(2+)-independent release of glutamate and GABA was not affected significantly by propofol (P > 0.05). Propofol could inhibit Ca(2+)-dependent release of glutamate and GABA. However, it has no effect on the Ca(2+)-independent release of glutamate and GABA.
Anesthetics, Intravenous/pharmacology ; Calcium/metabolism ; Glutamic Acid/*biosynthesis ; Hippocampus/*metabolism ; Propofol/*pharmacology ; Rats, Sprague-Dawley ; Synaptosomes/*metabolism ; gamma-Aminobutyric Acid/*biosynthesis

We studied the effect of carbon monoxide (CO)-induced hypoxia on synaptosomal uptake and release of dopamine (DA) in rat striatum. When the rats were intoxicated at a blood level of carboxyhemoglobin (HbCO), 60-70% for 3-4hrs, [3H] DA uptake was inhibited as much as 80% of control activity. This suppressed activity remained as long as 12 hrs after termination of the intoxication. After a week recovery period, the suppressed uptake activity was restored completely. When the rats were intoxicated maintaining a blood level of HbCO at 30-40% for 6-7hrs, the uptake was inhibited to 57% of the control actvity and this suppressed activity was restored within 12hrs. For the rats maintaining a blood level of HbCO at 15-25% for 6-7hrs, uptake inhibition was not shown. Acute CO intoxication(at 60-70% of HbCO for 3-4 hrs) caused an increase in K+-stimulated DA release to 147% of the control value. In conclusion, the diminished uptake and increased release of striatal DA in a CO intoxicated brain would cause an extraneuronal accumulation of DA with depletion of intraneuronal DA level, which may play a role in CO-induced hypoxic cell damage.
Animal ; Carbon Monoxide Poisoning/*complications ; Corpus Striatum/*ultrastructure ; Culture Media ; Dopamine/*metabolism ; Female ; Hypoxia, Brain/chemically induced/*pathology ; In Vitro ; Male ; Rats ; Synaptosomes/*metabolism

OBJECTIVETo explore the effect of organophosphorus insecticides (OPs) on the nicotinic autoreceptor function (NAF) in rat cortical synaptosomes and to understand alternative target of the OPs for human and other animals.

METHODSIn vitro experiment, synaptosomes from the rats were incubated with [(3)H] choline and then superfused with physiological buffer. The [(3)H] acetylcholine release from the synaptosomes after the addition of paraoxon or chlorpyrifos to the superfusion system was recorded and the changes of NAF were calculated. In vivo experiment, NAF and acetylcholinesterase (AChE) activity in the cortical synaptosomes in the adult rats dosed with chlorpyrifos were also determined 96 h after OPs treatment.

RESULTSParaoxon caused slight effect on NAF (average inhibition rate: < 23%) while chlorpyrifos oxon caused > 100% of inhibition on NAF in vitro. Chlorpyrifos markedly reduced NAF by 66% 96 h after treatment and inhibited the AChE activity by 91% in vivo.

CONCLUSIONThe OPs may have different effects on the NAF of rat cortical synaptosomes while chlorpyrifos may certainly inhibit the NAF in cortical synaptosomes of adult rats.

Acetylcholine ; secretion ; Animals ; Brain ; drug effects ; metabolism ; Chlorpyrifos ; toxicity ; In Vitro Techniques ; Insecticides ; toxicity ; Paraoxon ; toxicity ; Rats ; Receptors, Nicotinic ; physiology ; Synaptosomes ; drug effects ; metabolism

Lithium remains the most widely used therapeutic agent for bipolar affective disorder, particularly mania. Although many investigators have studied the effects of lithium on abnormalities in monoamine neurotransmitter as a pathophysiological basis of affective disorder, the action mechanism of lithium ion remains still unknown. To explore the action mechanism of lithium in the brain, we examined the effects of lithium on the extrasynaptosomal concentrations of catecholamines and their metabolites. Synaptosomes were prepared from the rat forebrains and assays of catecholamines and metabolites were made using HPLC with an electrochemical detector. Lithium of 1mM decreased the extrasynaptosomal concentrations of NE from the control group of 3.07+/-1.19 to the treated group of 0.00+/-0.00 (ng/ml of synaptosomal suspension) but not that of DHPG. It can be suggested that lithium increases synaptosomal uptake of NE. Increased intraneuronal uptake of NE would decrease neurotransmission and extraneuronal metabolism of NE. Because increased brain NE metabolism and neurotransmission have been suggested as important components in the pathophysiology of bipolar affective disorder, especially mania, lithium-induced increase of intraneuronal NE uptake can be suspected as an action mechanism of therapeutic effect of lithium in manic patient, possibly in bipolar affective disorder.
Animals ; Bipolar Disorder ; Brain* ; Catecholamines ; Chromatography, High Pressure Liquid ; Humans ; Lithium ; Metabolism ; Mood Disorders ; Neurotransmitter Agents ; Norepinephrine* ; Prosencephalon ; Rats* ; Research Personnel ; Synaptic Transmission ; Synaptosomes