An Ex Vivo Method for Evaluating Prostaglandin Synthetase Activity in Cortical Slices of Mouse Brain

The release of prostaglandin E2 (PGE2) from cortical slices of mice into incubation medium is followed for 3 h and compared to PGE2 levels in the corresponding slice. Immediately after decapitation, the rate of PGE2 released into the incubation medium is elevated and a steady low rate of spontaneous release is gained within 1-2 h of incubation. PGE2 synthesis and release is blocked in a dose-dependent manner by either indomethacin (3 X 10(-6) -3 X 10(-4) M) or flufenamic acid (2.6 X 10(-6) M) either when added in vitro or administered in vivo. Full recovery of PGE2 synthesis is reached after 3 h incubation of slices following in vivo administration of indomethacin. In vivo administration of flufenamic acid results in prolonged inhibition of PGE2 released in vitro. The inhibition of PGE2 released by indomethacin is also correlated with the slice PGE2 content. Administration of lipopolysaccharide (LPS), a known activator of phospholipase A2, results in a fivefold increase in PGE2 and a twofold increase in 6-keto-PGF1 alpha released into the medium. The release of thromboxane B2 is not affected by LPS.     

Identification and Characterization of Cysteinyl-Leukotriene Formation in Tissue Slices from Human Intracranial Tumors: Evidence for Their Biosynthesis Under In Vivo Conditions

In previous studies, it had been shown that human gray and white matter tissue slices have the capacity to synthesize large amounts of cysteinyl-leukotrienes (cysteinyl-LT) in vitro. This study was initiated to investigate cysteinyl-LT formation by tissue slices from intracranial tumors in comparison with cyclooxygenase products such as prostaglandin (PG) F2 alpha and thromboxane (TX) B2. Tissue slices from meningiomas and astrocytomas were found to release large amounts of cysteinyl-LT spontaneously and even higher amounts after ionophore A 23187 stimulation, which could not be accounted for by blood possibly remaining in the tissue slices. Cysteinyl-LT were identified by their immunoreactive characteristics, their biological activity in the guinea pig ileum bioassay, and their retention time on reversed-phase HPLC. With increasing malignancy, astrocytomas were shown to have an increasing biosynthetic capacity for cysteinyl-LT and TXB2 in vitro. In comparison with meningioma patients, malignant astrocytoma patients had an enhanced urinary excretion of LTE4, the major urinary metabolite of cysteinyl-LT in humans, which dropped in level within 7 days after operation by 79%. A correlation exists between the in vivo cysteinyl-LT production in patients with malignant astrocytomas and that observed under basal conditions in the tissue slices in vitro. The results provide evidence that in malignant astrocytoma patients, the tumor tissue produces large amounts of cysteinyl-LT, which may be detected in the patients' urine.     

Production of Hyperalgesic Prostaglandins by Sympathetic Postganglionic Neurons

Prostaglandin E2 and prostacyclin (prostaglandin I2) produce hyperalgesia in animals and humans. Because there is evidence that prostaglandins contribute to pain maintained by sympathetic nervous system activity, we evaluated whether sympathetic postganglionic neurons synthesize these hyperalgesic prostaglandins, and whether production of prostaglandins by these neurons can contribute to sensitization of primary afferent nociceptors. Intradermal injection of arachidonic acid but not linoleic acid, in the rat hindpaw, produces a decrease in mechanical nociceptive threshold. This hyperalgesic effect is prevented by indomethacin, an inhibitor of prostaglandin synthesis or by prior surgical removal of the lumbar sympathetic chain. To test the hypothesis that sympathetic postganglionic neurons are the source of prostaglandins, we measured production of prostaglandin E2 and 6-keto-prostaglandin F1 alpha (the stable metabolite of prostacyclin) by homogenates of adult rat sympathetic postganglionic neurons from superior cervical ganglia. These homogenates produced significant amounts of prostaglandin E2 and 6-keto-prostaglandin F1 alpha, and most of this production is eliminated by neonatal administration of 6-hydroxydopamine which selectively destroys sympathetic postganglionic neurons. These results demonstrate that sympathetic postganglionic neurons produce prostaglandins, and supports further the hypothesis that the release of prostaglandins from sympathetic postganglionic neurons contributes to the hyperalgesia associated with sympathetically maintained pain.     

Effects of Metabotropic Glutamate Receptor Agonists and Antagonists on D-Aspartate Release from Mouse Cerebral Cortical and Striatal Slices

The cytosolic release of L-glutamate has been held to be responsible for the increase in extracellular glutamate to toxic levels in the brain. The mechanism and regulation of this release was now studied in cerebral cortical and striatal slices with D-[³H]aspartate, a non-metabolized analogue of L-glutamate and a poor substrate for vesicular uptake. L-Glutamate and D-aspartate strongly stimulated the release in a concentration-dependent manner. Of the ionotropic glutamate receptor agonists, only kainate enhanced the basal release in the striatum. Of the metabotropic glutamate receptor ligands, the group I agonist (S)-3,5-dihydroxyphenylglycine (S-DHPG) failed to affect the basal release but inhibited the D-aspartate-evoked release in the striatum. The group I antagonist (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) had no effect on the basal release in either preparation but enhanced the L-glutamate-evoked release and inhibited the D-aspartate-evoked release in the striatum, not however in the cerebral cortex. The group II agonist (2S,2R,3R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG IV) and the group II antagonist (2S)-2-ethylglutamate (EGLU) were without effect on the basal, D-aspartate- and L-glutamate-evoked releases of D-[³H]aspartate in either preparation. The group III agonist L-serine-O-phosphate (L-SOP) failed to affect the basal release but reduced the D-aspartate-evoked release in the striatum. The group III antagonist (RS)-methylserine-O-phosphate (MSOP) failed to affect the basal release but increased the glutamate-evoked release and inhibited the D-aspartate-evoked release in the striatum. Both L-trans-pyrrolidine-2,4-dicarboxylate (L-trans-PDC) and (2S, 1S, 2R)-2-carboxycyclopropyl)glycine (L-CCG-III), transportable inhibitors of the high-affinity glutamate uptake, enhanced the basal release, more strongly in the striatum than in the cerebral cortex. L-CCG-III also increased the L-glutamate-evoked release in the striatum. Nontransportable dihydrokainate enhanced the basal release much less and failed to affect the glutamate-evoked release. The results indicate that the release of glutamate from cytosolic pools is carrier-mediated via homoexchange. This process is regulated in the striatum by metabotropic group I and group III receptors in a manner different from the regulation of the vesicular release of glutamate from presynaptic terminals.     

N-Methyl-d-Aspartate- and Non-N-Methyl-d-Aspartate-Evoked Adenosine Release from Rat Cortical Slices: Distinct Purinergic Sources and Mechanisms of Release

Abstract: Excitatory amino acids, acting at both N methyl- d -aspartate (NMDA) and non-NMDA receptors, release the inhibitory neuromodulator adenosine from superfused rat cortical slices. This study was initiated to investigate the possible purinergic sources and mechanisms of release for the adenosine release evoked by NMDA and non-NMDA receptor activation. Inhibition of the bidirectional nucleo-side transporter with dipyridamole greatly enhanced adenosine release evoked by glutamate, NMDA, kainate, and ( RS -α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). Inhibition of ecto -5'-nucleotidase with α,β-methylene ADP and GMP had no effect on either kainateor AMPA-evoked adenosine release, but it decreased glutamate- and NMDA-evoked adenosine release by 23 and 68%, respectively. A similar inhibition of NMDA-evoked adenosine release was observed with α,β-methylene ADP alone, indicating that the inhibitory effect was not due to the reported competitive inhibition of NMDA receptors by GMP. Finally, NMDA-evoked adenosine release, but not kainate- or AMPA-evoked release, was Ca²⁺ dependent. These results indicate that activation of non-NMDA receptors releases adenosine per se in a Ca²⁺-independent manner. In contrast, NMDA receptor activation releases primarily a nucleotide that is subsequently converted extracellularly to adenosine; in this case, release is Ca²⁺ dependent. Although neither NMDA- nor non-NMDA-evoked adenosine release occurs via the nucleoside transporter, this transporter does appear to be a major route for removal of adenosine from the extracellular space.     

Somatodendritic α2-Adrenoceptors in the Locus Coeruleus Are Involved in the In Vivo Modulation of Cortical Noradrenaline Release by the Antidepressant Desipramine

Abstract: The effect of the antidepressant and selective noradrenaline reuptake blocker desipramine (DMI) on noradrenergic transmission was evaluated in vivo by dual-probe microdialysis. DMI (1, 3, and 10 mg/kg, i.p.) dose-dependently increased extracellular levels of noradrenaline (NA) in the locus coeruleus (LC) area. In the cingulate cortex (Cg), DMI (3 and 10 mg/kg, i.p.) also increased NA dialysate, but at the lowest dose (1 mg/kg, i.p.) it decreased NA levels. When the α₂-adrenoceptor antagonist RX821002 (1 µ M ) was perfused in the LC, DMI (1 mg/kg, i.p.) no longer decreased but rather increased NA dialysate in the Cg. In electrophysiological experiments, DMI (1 mg/kg, i.p.) inhibited the firing activity of LC neurons by a mechanism reversed by RX821002. Local DMI (0.01–100 µ M ) into the LC increased concentration-dependently NA levels in the LC and simultaneously decreased NA levels in the Cg. This decrease was abolished by local RX821002 administration into the LC. The results demonstrate in vivo that DMI inhibits NA reuptake at somatodendritic and nerve terminal levels of noradrenergic cells. The increased NA dialysate in the LC inhibits noradrenergic activity, which in part counteracts the effects of DMI on the Cg. The modulation of cortical NA release by activity of DMI at the somatodendritic level is mediated through α₂-adrenoceptors located in the LC.     

Acute Uteroplacental Ischemic Embryo: Lactic Acid Accumulation and Prostaglandin Production in the Fetal Rat Brain

A new experimental model for studying the effects of acute ischemia on brain development in the near-term fetal rat has been devised. Ischemic conditions are achieved by complete clamping of blood vessels branching from the uterine vasculature into each individual fetus for designated times followed by removal of the clamps to permit reperfusion. Accumulation of lactic acid in the fetal brain depends on the length of the restriction period, reaching a plateau level of 29 mumol/g tissue at about 30 min. It also depends on the reperfusion time. Thus after a period of 15 min of restriction lactate levels show an increase over the next 30-min reperfusion to a value of 25.5 mumol/g followed by a rapid decrease to normal values by 3 h of reperfusion. Restriction of 15 min followed by reperfusion of 45 min causes an elevation of prostaglandin E2 (PGE2) level from 12.4 +/- 0.86 ng/g to 21.1 +/- 0.6 ng/g (p less than 0.001). This elevation in PGE2 level is less apparent after 20 min of restriction. No effects are seen on the level of PGF2 alpha. Both PGE2 and PGF2 alpha accumulate in vitro in a time-dependent manner by brain particulate fraction. In vitro synthesis of both PGE2 and PGF2 alpha is inhibited by indomethacin (100% and 68%, respectively) and AA861 (94% and 76%, respectively). BW755c and nordihydroguaiaretic acid do not affect PGE2 formation but enhance PGF2 alpha production by 112% and 152%, respectively. Particulate fractions from restricted brain produce less PGF2 alpha than control brains (6.38 +/- 1.62 versus 11.43 +/- 2.2, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of Tritiated Noradrenaline Release from the Rat Preoptic Area with Microdialysis In Vivo

Abstract: Present techniques are unable to provide a sensitive and accurate index of noradrenergic activity in the rat preoptic area. In this study, we have examined the brainstem A₁ noradrenergic input to the preoptic area using a new technique whereby [³H]noradrenaline is preloaded into the preoptic area and release of radioactivity from this region is measured subsequently using microdialysis in vivo. Electrical stimulation of the ipsilateral A₁ area for 20 min at 5, 10, and 15 Hz evoked significant increases in dialysate radioactivity that were repeatable and frequency-dependent. After removal of calcium from the perfusion medium, basal release of radioactivity was markedly reduced and the effect of A₁ stimulation abolished. Changing to a 100 mM K⁺ medium evoked an increase in the release of radioactivity that was sixfold greater than that seen after A₁ stimulation. Separation of the dialysate with HPLC showed that 33% of the increase in measured radioactivity after A₁ stimulation was directly attributable to [³H]noradrenaline and the remainder to the metabolites vanillylmandelic acid, 3,4-dihydroxymandelic acid, and 3,4-dihydroxyphenylglycol. In contrast, the increase in radioactivity after K⁺ depolarization was due almost completely to [³H]noradrenaline. Addition of 10 μM clonidine to the perfusion medium markedly reduced basal release of radioactivity, but had no effect on evoked release following A₁ stimulation. Conversely, perfusion with 10 μM yohimbine had no effect on basal release, but significantly increased evoked release after A₁ stimulation. These results now provide a characterization of noradrenergic activity in the preoptic area and indicate the importance of the A₁ noradrenergic input to this region. The technique of measuring radioactivity with microdialysis after preloading with [³H]noradrenaline provides a relatively simple, sensitive index of noradrenergic activity in vivo with good temporal resolution.     

Characterization of Brain Synaptic Vesicle Phospholipase A2 Activity and Its Modulation by Calmodulin, Prostaglandin E2, Prostaglandin F2α, Cyclic AMP, and ATP

Brain synaptic vesicle phospholipase A2 (PLA2) activity was characterized. It is Ca2+-dependent and has a pH optimum of 9.0. The enzyme has a Km of 60 microM and a Vmax of 2.0 nmol/mg/h. Calmodulin, prostaglandin F2 alpha, and cAMP, and ATP all increased the Vmax of the enzyme. Prostaglandin E2 inhibited the Vmax in the presence or absence of calmodulin. Light-scattering techniques in conjunction with phase-contrast and electron microscopy demonstrated that an increase in Vmax of PLA2 was correlated with synaptic vesicle aggregation, lysis, and possible fusion. In vitro synaptic vesicle-vesicle association that was stimulated by conditions that increased PLA2 activity could be diminished when synaptic vesicles were preincubated with PLA2 inhibitors. It is suggested that endogenous synaptic vesicle PLA2 activity may be an important mechanism underlying Ca2+-mediated neurotransmitter release.     

The Significance of Mast Cells as a Source of Histamine in the Mouse Brain

Abstract: Knowledge of the relative contributions of mast cells and neurons to the overall pool of histamine in the brain is a prerequisite to determining the significance and role of this amine in brain function. Consequently, we analyzed the levels of brain histamine in four genotypes (+/+, W/+, W^v/+ , and WIW^v ) of WBB6F₁ mice, whose numbers of brain-associated mast cells vary in a genotypically specific manner. Although mast cell numbers ranged from a total absence of mast cells (W/ W^v ) to an average of about 500 mast cells/brain ( W/+ ), no significant differences between genotypes were found in the quantities of histamine in whole brains, brain regions, or crude subcellular fractions. Thus, in this strain of mice, mast cells are not a significant source of histamine in the brain. This suggests that most of the histamine is of neuronal origin. Since neuronal histamine levels are maintained only by continued histidine decarboxylase activity, complete inhibition of this enzyme by α-fluoromethylhistidine, a "suicide" inhibitor of histidine decarboxylase, would totally deplete W/W^v mice of brain histamine. This was not found to occur in the W/W^v mice, suggesting that neuronal stores of histamine can be maintained in the absence of histidine decarboxylase, or that an additional nonneuronal, non-mast cell source of histamine exists in the W/W^v mouse brain.     

Effect of α-Amino-4-Phosphonobutyrate on the Release of Endogenous Glutamate and Aspartate from Cortical Synaptosomes of Epileptic Rats

The effect of the glutamate antagonist alpha-amino-4-phosphonobutyrate (APBA) on the release of endogenous amino acids from sensorimotor cortical synaptosomes of rats with a cortical cobalt focus and from non-epileptic rats was studied: (1) The release of endogenous glutamate, aspartate, and gamma-aminobutyric acid (GABA) from synaptosomal preparations of cobalt-induced epileptogenic tissues was increased compared with the release from the contralateral (sensorimotor) region or the sensorimotor cortex of normal animals. The intrasynaptosomal content of these amino acids was reduced in proportion to the amount released. The levels of other amino acids were unaffected or showed much smaller changes. (2) APBA (0.5-1 mM) decreased significantly the spontaneous release of aspartate and glutamate from the epileptic foci without affecting GABA or any other amino acid. (3) APBA produced no effect whatsoever on the release of any amino acid from synaptosomal preparations of nonepileptic focus.     

Release of Endogenous Taurine and γ-Aminobutyric Acid from Brain Slices from the Adult and Developing Mouse

The spontaneous and potassium-stimulated release of endogenous taurine and gamma-aminobutyric acid (GABA) from cerebral cortex and cerebellum slices from adult and developing mice was studied in a superfusion system. The spontaneous release of GABA was of the same magnitude in slices from adult and developing mice, but the spontaneous release of taurine was considerably greater in the adults. The potassium-stimulated release of GABA from cerebral cortex slices was about five times greater in adult than in 3-day-old mice, but the potassium-stimulated release of taurine was more than six times greater in 3-day-old than in adult mice. In cerebellar slices from 7-day-old mice, potassium stimulation also evoked a massive release of taurine, whereas the evoked release from slices from adult mice was rather negligible. Also in cerebellar slices the potassium-stimulated release of GABA exhibited the opposite quantitative pattern. The stimulated release of both GABA and taurine was partially calcium dependent. The results suggest that taurine may be an important regulator of excitability in the developing brain.     

Acetylcholine Release in the Rat Prefrontal Cortex In Vivo: Modulation by α2-Adrenoceptor Agonists and Antagonists

Abstract: We have previously shown that the release of acetylcholine (ACh) in the medial prefrontal cortex of the conscious rat, as measured by microdialysis, is increased following intraperitoneal injection of the selective α₂-adrenoceptor antagonist (+)-efaroxan. To characterize further the receptor pharmacology of this response, the effects of other selective α₂-adrenoceptor ligands were examined. The α₂-adrenoceptor antagonists idazoxan (2.5 and 20 mg/kg), atipamezole (2.5 mg/kg), and fluparoxan (10 mg/kg) increased ACh outflow by up to 250–325% of basal levels over a 3-h period following intraperitoneal injection. The α₂-adrenoceptor agonists UK-14304 (2.5 mg/kg) and guanabenz (2.5 mg/kg) reduced ACh outflow by 80 and 60%, respectively. Clonidine (0.00063–0.16 mg/kg) had no significant depressant effect and at 2.5 mg/kg increased ACh outflow to 233% of basal levels. These results indicate a modulatory role for α₂-adrenoceptors on the release of ACh in the rat prefrontal cortex in vivo. Based on the facilitatory effects produced by the antagonists alone, this α₂-adrenoceptor modulation appears to be tonic and inhibitory. The ability of α₂-adrenoceptor antagonists to enhance ACh outflow suggests a therapeutic usefulness in disorders where cortical ACh release deficits have been implicated.     

Glucocorticoids Provoke a Shift from α2- to α1-Adrenoreceptor Activities in Cultured Hypothalamic Slices Leading to Opposite Noradrenaline Effect on Corticotropin-Releasing Hormone Release

Abstract: We have shown previously that noradrenaline (NA) stimulated or inhibited the release of corticotropin-releasing hormone (CRH) according to the availability of adrenal steroids. The aim of the present work was to examine whether the changes in the NA modulation of CRH release from hypothalamic neurons result from a steroid-induced plasticity of the adrenergic transduction pathways. From anterior hypothalamic slices cultured in standard medium (i.e., containing adrenal steroids at a final dilution of 61 ± 9 ng/ml), (a) the stimulatory effect of NA on CRH release was reversed in a dose-dependent manner by increasing concentrations of the α₁-adrenoreceptor antagonist prazosin, (b) activation of protein kinase C by acute treatment with phorbol 12-myristate 13-acetate (0.5 µ M , 1 h) mimicked NA stimulation of CRH secretion, and (c) the activation of L-type Ca²⁺ channels by Bay K 8644 also produce an increased CRH secretion. In contrast, the inhibitory effect of NA on CRH secretion from slices cultured in steroid-free medium was markedly reversed by the α₂-adrenoreceptor antagonist yohimbine, by pretreatment with pertussin toxin, or by the addition of 4-aminopyridine, a K⁺-channel blocker. Acute treatment with phorbol 12-myristate 13-acetate did not change the inhibitory NA effect. Moreover, all these effects were reversed by daily corticosterone supplementation, for as long as they were tested. These results are consistent with a steroid-dependent change in the nature of adrenergic receptors and its associated transduction pathways involved in the regulation of CRH secretion in the hypothalamus.     

Effects of Cyclic AMP Analogues and Phosphodiesterase Inhibitors on K+-Induced [3H]Noradrenaline Release from Rat Brain Slices and on Its Presynaptic α-Adrenergic Modulation

The possible role of cyclic AMP in the presynaptic alpha-adrenoceptor-mediated modulation of [3H]noradrenaline (NA) release induced by 13 mM K+ from superfused rat cerebral cortex slices was investigated. Both dibutyryl-cyclic AMP (db-cAMP) and 8-bromo-cyclic AMP (8-Br-cAMP) dose-dependently (10(-4) - 10(-2) M) enhanced K+-induced (3H]NA release, maximally to about 160% of control. In contrast, db-cAMP had no effect on calcium-induced [3H]NA release in the presence of the calcium ionophore A 23187. Surprisingly, the phosphodiesterase (PDE) inhibitors 3-isobutyl-1-methylxanthine (IBMX). 7-benzyl-IBMX, 4-(3-cyclopentyloxy-4-methoxyphenyl)-2-pyrrolidone (ZK 62771), and 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro 20-1724) appeared to inhibit K+-induced [3H]NA release in a dose-dependent (10(-5) - 10(-3) M) manner. At a concentration of 10(-4) M, AK 62771 caused an inhibition of [3H]NA release by 30%, and this inhibitory effect was not affected by 10(-6) M phentolamine nor by 10(-3) M db-cAMP or 10(-4) M theophylline. Theophylline by itself enhanced [3H]NA release to about 135% of control. The inhibitor effect of the alpha-adrenoceptor agonist oxymetazoline (1 micro M) and the enhancing effect of the antagonist phentolamine (1 micro M) on [3H]NA release were significantly decreased in the presence of 10(-3) M db-cAMP or 8-Br-cAMP, whereas 10(-4) M ZK 62771 had no effect. In the presence of 10(-2) M NaF, a potent activator of adenylate cyclase, the inhibitory effect of oxymetazoline (1 micro M) on [3H]NA release was significantly decreased. The data obtained with the cyclic AMP analogues support the hypothesis that activation of presynaptic alpha-receptors modulating NA release results in an inhibition of a presynaptic adenylate cyclase. Possible causes for the anomalous effects of th PDE inhibitors are discussed.     

Measurement of Endogenous Noradrenaline Release in the Rat Cerebral Cortex In Vivo by Transcortical Dialysis: Effects of Drugs Affecting Noradrenergic Transmission

The release of endogenous noradrenaline was measured in the cerebral cortex of the halothane-anesthetized rat by using the technique of brain dialysis coupled to a radioenzymatic assay. A thin dialysis tube was inserted transversally in the cerebral cortex (transcortical dialysis) and perfused with Ringer medium (2 microliter min-1). Under basal conditions, the cortical output of noradrenaline was stable over a period of at least 6 h and amounted to 8.7 pg/20 min (not corrected for recovery). Histological control of the perfused area revealed very little damage and normal morphology in the vicinity of the dialysis tube. Omission of calcium from the perfusion medium caused a marked drop in cortical noradrenaline output. Bilateral electrical stimulation (for 10 min) of the ascending noradrenergic pathways in the medial forebrain bundle caused a frequency-dependent increase in cortical noradrenaline output over the range 5-20 Hz. Stimulation at a higher frequency (50 Hz) resulted in a levelling off of the increase in cortical noradrenaline release. Systemic administration of the dopamine-beta-hydroxylase inhibitor bis-(4-methyl-1-homopiperazinylthiocarbonyl) disulfide (FLA 63) (25 mg/kg i.p.) markedly reduced, whereas injection of the monoamine oxidase inhibitor pargyline (75 mg/kg i.p.) resulted in a progressive increase in, cortical noradrenaline output. d-Amphetamine (2 mg/kg i.p.) provoked a sharp increase in cortical noradrenaline release (+450% over basal values within 40 min). Desmethylimipramine (10 mg/kg i.p.) produced a twofold increase of cortical noradrenaline release. Finally, idazoxan (20 mg/kg i.p.) and clonidine (0.3 mg/kg i.p.), respectively, increased and decreased the release of noradrenaline from the cerebral cortex.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of Fructose-1,6-Bisphosphate on Glutamate Release and ATP Loss from Rat Brain Slices During Hypoxia

Abstract: Fructose-1,6-bisphosphate (FBP), an intermediate of glucose metabolism, is neuroprotective in brain hypoxia or ischemia. Because the mechanisms for this protection are not clear, we examined the effects of FBP on two important events in brain ischemia, i.e., loss of ATP and release of the excitatory neurotransmitter glutamate. Glutamate release from cortical brain slices was measured fluorometrically (glutamate dehydrogenase)-catalyzed conversion of glutamate to α-ketoglutarate) during hypoxia (Po₂ 15 mm Hg) or hypoxia plus 100 µ M cyanide. FBP (3.5 m M , with glucose 20 m M ) reduced glutamate release during hypoxia by 55% and during hypoxia/cyanide by 46% ( p < 0.005), and prevented a significant fall in [ATP]. [ATP] was maintained in oxygenated glucose-free conditions with 20 but not 3.5 m M FBP, and fell to <20% of normal with hypoxia. Despite the drop in [ATP], 3.5 or 20 m M FBP without glucose decreased hypoxia-evoked glutamate release. We conclude (1) FBP present without glucose preserves normal [ATP] only when oxygen is available, suggesting limited uptake and metabolism; and (2) FBP decreases hypoxia-evoked glutamate release by processes independent of [ATP]. These results suggest protective actions of FBP that are separate from augmentation of anaerobic energy production, as previously proposed.     

Roles of Prostaglandins D2 and E2 in Interleukin-1-Induced Activation of Norepinephrine Turnover in the Brain and Peripheral Organs of Rats

Abstract: Possible roles of prostaglandins (PGs) in interleukin-1 (IL-1)-induced activation of noradrenergic neurons were examined by assessing norepinephrine (NE) turnover in the brain and peripheral organs of rats. An intraperitoneal injection of human recombinant IL-1β accelerated NE turnover in the hypothalamus, spleen, lung, diaphragm, and pancreas. A similar increase in NE turnover was also observed after intracerebroventricular injection of corticotropin-releasing hormone (CRH). Pretreatment with indomethacin (cyclooxygenase inhibitor) abolished the IL-1-induced, but not the CRH-induced, increase in hypothalamic and splenic NE turnover. To elucidate which eicosanoid-cyclooxygenase product(s) is responsible for accelerating NE turnover, PGD₂, PGE₂, PGF_2α, U-46619 (stable thromboxane A₂ analogue), or carbacyclin (stable prostacyclin analogue) was administered intracerebroventricularly. Among them, PGE₂ was the only eicosanoid effective in increasing NE turnover in spleen, whereas PGD₂ was effective in the hypothalamus. The stimulative effect of PGD₂ was abolished by pretreatment with intracerebroventricular injection of a CRH antiserum. These results suggest that the action of IL-1 is mediated through PGD₂ production to activate the noradrenergic neurons in the hypothalamus, and through PGE₂ production to increase sympathetic nerve activity in spleen.     

Comparison of the Effects of a Convulsant Barbiturate on the Release of Endogenous and Radiolabeled Amino Acids from Slices of Mouse Hippocampus

The convulsant barbiturate 5-(2-cyclohexylidene-ethyl)-5-ethyl barbituric acid (CHEB) stimulates the spontaneous release of endogenous and radiolabeled acetylcholine (ACh) from mouse hippocampal slices in vitro. In order to determine if the ability of CHEB to release ACh was unique to this neurotransmitter, we have studied the action of this drug in vitro on the release of both radiolabeled and endogenous putative neurotransmitter and non-transmitter amino acids in the hippocampus. Although CHEB stimulated the spontaneous release of both [3H]gamma-n-aminobutyric acid (GABA) and endogenous GABA, CHEB had different effects on the spontaneous release of radiolabeled and endogenous L-glutamate and L-aspartate: L-[3H]glutamate release was inhibited by CHEB, but endogenous L-glutamate release was unaffected by CHEB, but endogenous L-aspartate release was stimulated. The spontaneous release of the amino acids L-alanine and glycine (not thought to be neurotransmitters in the hippocampus) was not affected by CHEB. The results of this study indicate that CHEB does not always stimulate the release of all putative neurotransmitters. The ability of this drug to release ACh, GABA, and L-aspartate may be the result of some specific interaction of CHEB with nerves using these neurotransmitters in the hippocampus. In addition, the results suggest some problems that may be encountered when radiolabeled substances are used to study neurotransmitter release.     

丙泊酚与七氟醚用于后腹腔镜手术患者对血浆TXB2, ET-1, D-D水平的影响比较

目的:比较丙泊酚与七氟醚用于后腹腔镜手术患者对血浆血栓烷素B2(TXB2)、内皮素-1(ET-1)、D-二聚体(D-D)水平的影响。方法:研究对象选自我院2015年5月~2016年12月收治的行后腹腔镜手术治疗的84例患者,采取随机数字表将其分成两组,每组42例。两组患者麻醉诱导相同,观察组麻醉维持采取2%~3%七氟醚持续吸入,对照组给予丙泊酚4~12 mg/(kg·h)持续泵注,两组同时给予瑞芬太尼10μg/(kg·h)靶控输注。分别于麻醉诱导后(T0)、气腹后0.5 h(T1)、1 h(T2)、1.5 h(T3)时点检测两组患者的血浆TXB2、ET-1、D-D含量,同时比较两组麻醉效果以及不良反应的发生情况。结果:观察组意识消失时间、气管插管时间、自主呼吸恢复时间、睁眼时间、言语应答时间、定向力恢复时间、拔管时间均显著短于对照组(P0.01)。两组不良反应发生情况对比差异无统计学意义(P0.05)。两组患者T1、T2、T3时点的血浆TXB2、ET-1、D-D含量均逐渐升高,且均明显高于T0(P0.01);观察组患者T1、T2、T3时点的血浆TXB2、ET-1、D-D含量均显著低于对照组同时点(P0.01)。结论:后腹腔镜手术可引起不同程度的血液高凝状态。与丙泊酚相比,七氟醚用于后腹腔镜手术麻醉中可有效抑制TXB2、ET-1、D-D的释放,能起到更好抗凝作用。