Effects of polychlormated biphenyls on dopamine release from PC 12 cells

In PC12 cells, Aroclor 1254 produced a concentration-dependent decrease in basal and K ⁺-evoked dopamine (DA) release, and cellular DA levels. Aroclor 1254 did not alter the fraction of cellular DA released, suggesting that the decreased release of DA was solely due to decreased cellular levels of DA, and not to decreased packaging of DA or inhibition of neurotransmitter release. The coplanar congener 3,3′,4,4′,5-pentachlorobiphenyl decreased cellular DA levels and release of DA at levels that produced cytotoxicity. Absent of any apparent cytotoxicity, the ortho-substituted PCB congeners 2,2′,5,5′-tetrachlorobiphenyl, 2,2′,3,3′,4,4′-hexachlorobiphenyl, 2,3′,4,4′,5-pentachlorobiphenyl, and 2,2′,4,4′,5,5′-hexachlorobiphenyl were effective in decreasing the amount of DA released from PC12 cells. These results suggest that ortho-chlorinated PCBs can cause decreased K⁺-evoked DA release through non-Ah receptormediated mechanisms. Furthermore, the PCB-mediated decrease m DA release was not due to impairment of DA packaging or release, but only due to decreased cellular DA levels.     

人参皂苷Rg1和Rb1促进PC12细胞释放谷氨酸的作用机制

目的研究人参皂苷(ginsenosides)Rg1和Rb1促进PC12细胞释放谷氨酸作用的机制。方法HPLC法测量PC12细胞释放谷氨酸的含量。细胞免疫染色法和Western blotting法检测人参皂苷Rg1和Rb1对突触蛋白(synapsins)磷酸化水平的影响。结果人参皂苷Rg1(10 μmol·L^-1)和Rb1(10 μmol·L^-1)均可明显促进PC12细胞中谷氨酸的释放。加入蛋白激酶A(PKA)抑制剂H89可抑制Rb1诱导的谷氨酸释放增加；但H89不能抑制Rg1诱导的谷氨酸释放增加。Rb1可升高PC12细胞中突触蛋白的磷酸化水平，H89可抑制这种作用；而Rg1对突触蛋白磷酸化水平无明显作用。结论Rb1可介导PKA活化以诱导突触蛋白磷酸化升高，进而引起谷氨酸释放增加；并提示Rg1促进谷氨酸释放的作用可能与突触蛋白磷酸化无关。     

Enhancement of arachidonic acid release and prostaglandin F(2alpha) formation by Na3VO4 in PC12 cells and GH3 cells

Both activation of phospholipase A2 causing arachidonic acid release and tyrosine phosphorylation have been proposed to be involved in neuronal functions. Previously, we reported that orthovanadate (Na3VO4), an inhibitor of tyrosine phosphatases, stimulated tyrosine phosphorylation in proteins and enhanced Ca2+-induced noradrenaline release in rat pheochromocytoma PC12 cells. However, the role of tyrosine phosphorylation on phospholipase A2 activity and/or arachidonic acid release in neuronal cells has not been well established. The effects of Na3VO4 on arachidonic acid release and prostaglandin F(2alpha) formation were investigated in two types of neuronal cell lines. In PC12 cells, addition of Na3VO4 stimulated [3H]arachidonic acid release and prostaglandin F(2alpha) formation in a concentration-dependent manner. Co-addition of 5 mM Na3VO4 enhanced ionomycin-stimulated [3H]arachidonic acid release. Na3VO4 also enhanced ionomycin-stimulated [3H]arachidonic acid release from GH3 cells, a clonal strain from rat anterior pituitary. These findings suggest that the tyrosine phosphorylation pathway regulates arachidonic acid release by phospholipase A2 and prostaglandin F(2alpha) formation in neuronal cells.     

Angiotensin II stimulates arachidonic acid release from bone marrow stromal cells.

INTRODUCTION: Angiotensin II (Ang II) is recognised as a regulator of haematopoiesis, but its actions within the bone marrow are not fully understood. Support of haematopoiesis by bone marrow stromal cells (MSC) is dependent on factors that include arachidonic acid and macrophage colony stimulating factor (MCSF), both of which are increased by Ang II stimulation in other tissues. To further elucidate the mechanisms of Ang II-regulated haematopoiesis, we determined whether Ang II-stimulation alters arachidonic acid release and MCSF secretion from MSC. METHODS: Cynomolgus monkey MSC isolated from bone marrow aspirates and the human HS-5 stromal cell line were studied for Ang II-mediated arachidonic acid (AA) release, while secretion of MCSF in response to Ang II was studied in HS-5 cells. Cells were labelled overnight with 3H-AA and the release of 3H-AA was measured in culture medium following 20 minutes stimulation with Ang II, alone or in combination with the AT1- or AT2-receptor antagonists, losartan and PD 123319, respectively. MCSF secretion into culture medium was measured using an enzyme immunoassay following 24 hours of treatment with Ang II alone or in combination with losartan or PD 123319. Phorbol-myristate-acetate, known to stimulate release of AA and MCSF, was used as a positive control in both experiments. RESULTS: In response to Ang II, release of 3H-AA from monkey and human MSC was increased (p<0.05) to 147+/-4% and 124+/-3% of control, respectively. The AT1- and AT2-receptor antagonists, losartan and PD 123319, individually reduced Ang II-stimulated 3H-AA release. In contrast, Ang II had no effect on secretion of MCSF from HS-5 cells. CONCLUSIONS: These results provide mechanistic evidence for Ang II-mediated haematopoiesis through AA release that may, in part, explain Ang II-facilitated recovery of haematopoiesis in experimental myelosuppression and the anaemias associated with Ang II receptor blockade.     

Effect of amiloride on arachidonic acid and histamine release from rat mast cells

The effect of a putative Na+/H+ exchange inhibition on histamine and [14C]arachidonic acid ([14C]AA) release has been examined in rat peritoneal mast cells, using either addition of amiloride or removal of extracellular Na+. The cells were stimulated by non-immunological agents, i.e. calcium ionophore A23187, nerve growth factor (NGF), thapsigargin and compound 48/80. On the basis of the results obtained, a possible role for Na+/H+ exchange in rat mast cell secretion is discussed.     

Carrageenan-stimulated release of arachidonic acid and of lactate dehydrogenase from rat pleural cells

Cells isolated from the rat pleural cavity consist mainly of macrophages, mast cells, eosinophils, and lymphocytes. Isolated pleural cells labeled with [14C]arachidonic acid released appreciable amounts (approximately 12%) of radiolabel upon exposure to pharmacological concentrations of carrageenan (1-100 micrograms/ml). The release of radiolabel was decreased by an inhibitor of phospholipase A2 (p-bromophenacyl bromide) but not by an inhibitor of arachidonate cyclooxygenase (indomethacin). The released products were arachidonic acid and, to a much lesser extent, prostaglandin E2 and leukotriene C4. The release of radiolabel was associated with release of cytosolic lactate dehydrogenase over the same range of carrageenan concentrations. Time-course studies indicated that release of radiolabel preceded that of lactate dehydrogenase. Since p-bromophenacyl bromide blocked stimulated release of radiolabel but did not prevent release of lactate dehydrogenase, it is unlikely that increase in arachidonate causes carrageenan-induced cell damage. Nevertheless, the question of whether the activation of phospholipase A2 in the pleural cells, most probably the macrophages, was sufficient to initiate the carrageenan-induced inflammatory response requires further study. Cytotoxicity which was apparent with as little as 5 micrograms/ml of carrageenan, may have been a significant consequence of carrageenan action.     

Histamine release from serosal mast cells by intermediate products of arachidonic acid metabolism

In the present paper we report the results of experiments carried out to measure the release of histamine from isolated rat mast cells during the metabolic activation of arachidonic acid. Arachidonic acid (10(-8)-10(-4) M) and the terminal products (10(-6) M) of the arachidonic acid pathways were devoid of any significant histamine releasing properties. A substantial amount of histamine was released from rat mast cells by low concentrations of arachidonic acid during incubation with prostanoid generating systems, such as guinea-pig lung microsomes, rat serosal macrophages and polymorphonuclear cells and prostaglandin-H-synthase from calf seminal vesicles. The release of histamine was not accompanied by a leakage of lactate dehydrogenase and was blocked by D-mannitol and by lipoxygenase and cyclooxygenase pathway inhibitors. The data are consistent with the hypothesis that free radical derivatives of arachidonic acid, originating from hydroperoxy fatty acids, are generated during catalysis, causing mast cell histamine release.     

7-OH-DPAT-induced inhibition of norepinephrine release in PC12 cells

The purpose of this study was to investigate mechanisms of suppression of norepinephrine release by 7-OH-DPAT, a dopamine D(2)/D(3) receptor agonist, in PC12 cells pretreated with nerve growth factor (NGF). 7-OH-DPAT caused inhibition of basal and K(+)-evoked norepinephrine release, which could be blocked by pretreatment with raclopride, a D(2)/D(3) receptor antagonist. Moreover, dopamine D(2) and D(3 )receptors were identified by immunocytochemistry. Expression of D(2), D(3), and D(4) mRNAs and their proteins were detected using RT-PCR and immunoblotting. Furthermore, 7-OH-DPAT produced no change in cGMP levels; however, 7-OH-DPAT inhibited forskolin-stimulated cAMP accumulation that was antagonized by pretreatment with raclopride. In addition, 7-OH-DPAT inhibited carbachol-induced Ca(2+) transient, conversely, 7-OH-DPAT had no effect on 4-aminopyridine-induced Ca(2+) transient. Taken together, suppression of cAMP accumulation and calcium mobilization by 7-OH-DPAT is involved in the inhibition of norepinephrine release through activation of dopamine D(2)/D(3) receptors.     

Lanthanum suppresses arachidonic acid-induced cell death and mitochondrial depolarization in PC12 cells

Within the framework of studying the mechanisms of acute toxicity of arachidonic acid and the role of ambient cations, we have investigated the effects of extracellular La(3+) on arachidonic acid-induced death (lactate dehydrogenase release) and mitochondrial depolarization (rhodamine 123 fluorescence) in PC12 cells. Micromolar La(3+) profoundly suppressed arachidonic acid toxicity and this effect was dependent on the presence of other cations. Whereas in the cation-free solution 10-20 microM La(3+) protected most cells from death caused by a 2 hour-long exposure to 20 microM arachidonic acid, the cytoprotective effect of 100 microM La(3+) was reduced to approximately 70% in the presence of a normal complement of monovalent cations and was hardly detectable with 5 mM Ca(2+) in the bath. Increasing the concentration of arachidonic acid could defeat La(3+) cytoprotection. In fluorescence experiments, arachidonic acid caused a decrease in the mitochondrial membrane potential, with the rate and extent of depolarization increasing with an increase in the concentration of arachidonic acid. La(3+) countered the depolarizing effect of arachidonic acid in a manner consistent with a decrease in the effective arachidonic acid concentration. The results suggest that extracellular cations modulate cellular effects of arachidonic acid by reducing its ability to pass through the plasma membrane, possibly by binding the fatty acid. The similarities of the La(3+) effects on arachidonic acid-induced cell death and arachidonic acid-induced mitochondrial depolarization strongly support the causal relations between the two events and suggest that mitochondria are the primary target of arachidonic acid at the cellular level.     

Mechanism of dopamine mediated inhibition of neuropeptide Y release from pheochromocytoma cells (PC12 cells)

In rat pheochromocytoma (PC12) cells the dopamine D(2) receptor agonists apomorphine (APO) and n-propylnorapomorphine (NPA) produced a concentration dependent inhibition of K(+)-evoked neuropeptide Y release (NPY-ir). The effect of APO was blocked by the dopamine D(2)-receptor antagonist, eticlopride, but not the D(1)/D(3) or the D(4)/D(2) antagonists, SCH23390 or clozapine, respectively. The D(1)/D(5) receptor agonist, SKF38393 or the D(3) agonists PD128907 and 7-OH DPAT had no effect. Selective N and L-type voltage gated Ca(2+) channel blockers, omega-conotoxin GVIa (Ctx-GVIa) and nifedipine, respectively, produced a concentration dependent inhibition of NPY-ir release but were not additive with APO. The Ca(2+)/calmodulin-dependent protein kinase (CaM kinase) II inhibitor KN-62 produced a concentration-dependent inhibition of NPY-ir release but the combination of KN-62 and APO produced no further inhibition. PMA-mediated protein kinase C stimulation significantly increased both basal and K(+)-evoked release of NPY-ir, and in the presence of PMA APO had no inhibitory effect. The PKC antagonist, chelerythrine, inhibited K(+)-evoked NPY-ir release but was not additive with APO. Neither forskolin-mediated adenylate cyclase activation and the active cAMP analog Sp-cAMPS, nor the adenylate cyclase inhibitor SQ 22536, and the competitive inhibitor of cAMP-dependent protein kinases Rp-cAMPS, had any significant effect on K(+)-evoked NPY-ir release. This suggests the inhibitory effect of APO on K(+)-evoked release of NPY-ir from PC12 cells is most likely mediated through activation of dopamine D(2) receptors leading to direct inhibition of N and L-type voltage gated Ca(2+) channels, or indirect inhibition of PKC, both of which would reduce [Ca(2+)](i) and inactivate CaM kinase.     

Effects of inhibitors of arachidonic acid metabolism on serotonin release from rat basophilic leukemia cells

Mast cells can release arachidonic acid (AA) metabolites as well as preformed mediators with IgE mediated stimulation, and these mediators are considered to play an important role in allergic reactions. The coincident release of preformed mediators and AA metabolites suggests that AA metabolism is related to mast cell degranulation. To clarify the relationship between mast cell degranulation and AA metabolism, the effects of various AA cascade inhibitors on rat basophilic leukemia cell (RBL) mediator release induced by either anti-IgE or A23187 were examined. 5,8,11,14-eicosatetraynoic acid (ETYA) inhibited both PGD₂ and LTC₄/D₄ generation, and partially inhibited serotonin release. Nordihydroguaiaretic acid (NDGA) caused complete inhibition of LTC₄/D₄ generation, and partial inhibition of PGD₂ generation and serotonin release. The cyclooxygenase inhibitor, indomethacin, and the specific 5-lipoxygenase inhibitor, L-651,392 completely inhibited PGD₂ and LTC₄/D₄ generation, respectively, without affecting release of other mediators. Both PGD₂ and LTC₄/D₄ generation were abolished by the combination of indomethacin and L-651,392, however, serotonin release remained intact. HPLC analysis showed that no shift to other AA metabolites occurred after the treatment with these inhibitors. Mepacrine, a phospholipase A₂ inhibitor, completely inhibited PGD₂ and LTC₄/D₄ generation, as well as AArelease itself, without affecting serotonin release. Therefore, neither AA metabolism nor AA release is necessary for RBL degranulation.     

Characterization of bradykinin receptors mediating catecholamine release in PC12 cells

The rat pheochromocytoma cell line PC12, which is a widely used model for analyzing stimulus-secretion coupling, was investigated for the effects of kinins on catecholamine release. Subtypes of kinin receptors were characterized using the B₁ agonist desArg⁹-bradykinin, the B₂ agonist bradykinin and the B₂ antagonists [Thi^5,8, D-Phe⁷]-bradykinin, D-Arg[Hyp³, D-Tic⁷, Oic⁸]-bradykinin (HOE 890307) and D-Arg-[Hyp³, Thi⁵, D-Tic⁷, Oic⁸]-bradykinin (HOE 140). The effectiveness of acute and chronic exposure to angiotensin I converting enzyme inhibitors as well as pretreatment of the cells with bacterial lipopolysaccharides in modulating B₁ or B₂ receptor systems was also tested.Bradykinin stimulated noradrenaline release from PC12 cells at low concentrations (EC₅₀ = 1 nM), maximally inducing a release of 43.7% of the cellular content within 15 min. In comparison with acetylcholine and K⁺-induced depolarization, bradykinin was the most effective stimulus. DesArg⁹-bradykinin was only effective at very high concentrations (> 30 M). Like in other neuronal cells, the B₂-specific partial antagonist [Thi^5,8, D-Phe⁷]-bradykinin acted as a low-affinity agonist without any antagonistic effects. The B₂ antagonists HOE 890307 and HOE 140 exerted no agonistic effects and concentration-dependently inhibited bradykinin-induced noradrenaline release, showing competitive antagonism with K_i values of 1.38 nM and 0.66 nM, respectively. Only at the highest concentration used (1 M), HOE 140 did depress the maximal response to bradykinin. HOE 890307 also abolished the effects of desArg⁹-bradykinin and [Thi^5,8, D-Phe⁷]-bradykinin. Acute or chronic inhibition of the angiotensin I converting enzyme or application of lipopolysaccharides, which all can lead to induction of the B₁ receptor subtype in vivo, did not alter the secretory response of PC12 cells to either bradykinin (0.1 and 30 nM) or desArg⁹-bradykinin (1 M).In conclusion, noradrenaline release from PC12 cells is stimulated via B₂, but not B₁, receptors. Despite the fact that the receptor system is highly susceptible to stimulation by low-affinity ligands, HOE 890307 and HOE 140 are pure antagonists, with only high concentrations of HOE 140 (> 1 M) showing a non-competitive type of inhibition. Induction of B₁ receptors which could stimulate noradrenaline release could not be demonstrated in this model. The possible role of bradykinin in modulating sympathetic neurotransmission during inhibition of angiotensin I converting enzyme is discussed.     

PCB 50 stimulates release of arachidonic acid and prostaglandins from late gestation rat amnion fibroblast cells

Amniotic phospholipase A2 activity contributes to elevated levels of arachidonic acid and prostaglandins observed during labor. Polychlorinated biphenyls (PCBs) activate PLA2 and have been associated with shortened gestation length. To determine if PCBs stimulate amniotic PLA2, cell cultures of rat amnion fibroblasts (RAF) were established from gestation day (gd) 20 rats and labeled with 0.5 micro Ci [3H]-arachidonic acid prior to a 0.5- or 4-h exposure to 0.1% DMSO (solvent control), PCB 50 (1-50 micro M) or TNFalpha (positive control). PCB 50 and TNFalpha induced significant release of [3H]-arachidonic acid from amnion fibroblast cells in time-dependent manners (p<0.001), an effect associated with a significant increase in iPLA2 expression (p<0.05). PCB 50 also stimulated prostaglandin production from RAF cells independent of changes in immunoreactive COX-2. These data suggest that amnion may serve as a target for PCB-induced release of arachidonic acid and uterotonic prostaglandins, with a potential for adverse pregnancy outcomes.     

Vesicular catecholamine release from rat PC12 cells on acute and subchronic exposure to polychlorinated biphenyls

Effects of selected polychlorinated biphenyls (PCBs) on vesicular catecholamine release from rat PC12 phaeochromocytoma cells have been measured using carbon fiber microelectrode amperometry. Exocytotic responses were evoked by superfusion of single PC12 cells with high K(+) saline. Subsequent exposure of the same cells to saline containing the nonplanar congener 2,2'-dichlorobiphenyl (PCB 4) and the coplanar congener 3,3',4,4',5-pentachlorobiphenyl (PCB 126) at concentrations between 5 and 25 microM for 15 min caused an enhancement of the frequency of basal vesicular catecholamine release at the lower concentrations but not at the high concentrations tested. The nonplanar congener 2,2',3,3',4,4'-hexachlorobiphenyl (PCB 128) did not affect basal release. The PCBs caused only marginal effects on the frequency of evoked events during high K(+) stimulation and did not affect vesicle contents. Prolonged exposure of PC12 cells to low concentrations of the same PCBs in the culture medium for a period of 3 days did not cause significant changes in vesicle contents. The results demonstrate that low concentrations of PCBs may cause acute vesicular catecholamine release but do not influence the contents of catecholamine-containing vesicles either on acute or after subchronic exposure.     

N-ethylmaleimide-stimulated arachidonic acid release in human platelets

Treatment of human platelets with the alkylating agent N-ethylmaleimide (NEM) induces arachidonic acid release. The effect was time- and dose-dependent. NEM-stimulated arachidonic acid mobilisation could be prevented by pretreating platelets with the cytosolic phospholipase A2 (cPLA2)-specific inhibitor arachidonyltrifluoromethyl ketone. Moreover, the tyrosine kinase inhibitor genistein was able to significantly inhibit arachidonic acid mobilisation. NEM-stimulated release of arachidonic acid appears to be a Ca2+-dependent mechanism, as shown by the observation that arachidonic acid mobilisation was significantly reduced by platelet treatment with EGTA and abolished by preloading platelets with the intracellular chelator 1,2-bis (o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid tetra (acetoxymethyl) ester (BAPTA/AM). In Fura-2-loaded platelets, NEM was able to significantly increase the intracellular Ca2+ level. The Ca2+ elevation was significantly reduced in the presence of EGTA and suppressed by cell treatment with BAPTA/AM. Arachidonic acid released by NEM produced a significant increase in reactive oxygen species (ROS) intracellular levels, which was partially inhibited by diphenyleneiodonium and almost completely suppressed by 5,8,11,14-eicosatetraynoic acid. In conclusion, the results in this study demonstrate that NEM stimulates arachidonic acid release by cPLA2 activation through intracellular Ca2+ elevation. In addition, tyrosine specific protein kinases seem to be involved in arachidonic acid release. ROS was also shown to be formed during arachidonic acid metabolisation.     

Protocatechuic acid from Alpinia oxyphylla against MPP+-induced neurotoxicity in PC12 cells.

An ethyl acetate extract of Alpinia oxyphylla was found to possess neuroprotective activity against 1-methyl-4-phenylpyridinium ion (MPP(+)) induced apotosis and oxidative stress in cultured PC12 cells. From the extract, a phenolic compound was isolated through bioassay-guided fractionation and identified as protocatechuic acid (PCA) by IR, MS, and (1)H and (13)C NMR spectroscopy. It was the first time which was isolated from the kernels of A. oxyphylla. Exposure of PC12 cells to 1mM MPP(+) may cause significant viability loss and apoptotic cell death. PCA stimulated PC12 cellular proliferation and markedly attenuated MPP(+)-induced apoptotic cell death in a dose-dependent manner. By observing the nuclear morphological changes and flow cytometric analysis, PCA showed its significant effect on protecting PC12 cells against MPP(+)-induced apoptosis. Meanwhile, PCA enhanced the activities of superoxide dismutase (SOD) and catalase (CAT) in PC12 cells. In addition, PCA also dose-dependently reduced the hydrogen peroxide (H(2)O(2))- or sodium nitroprusside (SNP)-induced cell death in PC12 cells. The results suggest that PCA may be one of the primary active components in the kernels of A. oxyphylla and provide a useful therapeutic strategy for the treatment of oxidative stress-induced neurodegenerative disease such as Parkinson's disease.     

Calcium dependency of inhibition by arachidonic acid of compound 48/80-induced histamine release from mast cells

Compound 48/80 ( compd 48/80)-induced histamine secretion from rat mast cells was inhibited almost completely by pretreatment of the cells at 37 degrees with 25 microM arachidonic acid in the presence of 1.8 mM Ca2+. As the Ca2+ concentration was reduced below 1.8 mM, 25 microM arachidonic acid became less inhibitory and, then, progressively more stimulatory for histamine release with or without compd 48/80. No additive effect on histamine release was obtained by combining compd 48/80 and arachidonic acid. Pretreatment of mast cells with lidocaine, an inhibitor of Ca2+ binding to phospholipid, or with nordihydroguaiaretic acid, an inhibitor of Ca2+ flux and lipoxygenase, stimulated arachidonic acid-induced histamine release. Arachidonic acid also inhibited a compd 48/80-induced spike increment of intracellular 45Ca2+ uptake and a decrease of total 45Ca2+ uptake by 45Ca2+-preloaded mast cells. Arachidonic acid and Ca2+ also suppressed melittin-induced histamine release and compd 48/80-induced release of radioactivity from mast cells preloaded with [3H]arachidonic acid. These results suggest that exogenous arachidonic acid or its metabolite(s) may interact with membrane-associated Ca2+, disturbing Ca2+ availability for the trigger mechanism of compd 48/80-induced histamine release or inhibiting the subsequent metabolism of arachidonic acid via the lipoxygenase pathway to form active metabolites involved in the histamine liberating mechanism.     

Enhanced amphetamine-mediated dopamine release develops in PC12 cells after repeated amphetamine treatment

The present study tests the activity of nootropic drugs in a behavioral test linked to depression. This test measures the reduction of submissive behavior in a competition test as the relative success of two food-restricted rats to gain access to a feeder. Nootropic drugs tested include piracetam (2-oxo-1-pyrrolidineacetamide), aniracetam (1-(4-methoxybenzoyl)-2-pyrrolidinone), the Ampakine, Ampalex, 1-(quinoxalin-6-ylcarbonyl)piperidine, and analogs were compared to the antidepressants, fluoxetine ((+/-)-N-methyl-gamma-(4-[trifluoromethyl]phenoxy)-benzenepropanamine) and desimpramine (5H-dibenz[b,f]azepine-5-propanamine, 10,11-dihydro-N-methyl-, monohydrochloride), while the anxiolytic diazepam (7-chloro-1-methyl-5-phenyl-3H-1,4-benzodiazepin-2(1H)-one) served as a control. Drugs were given intraperitoneally for 3 weeks. The antidepressant and nootropic drugs reduced submissive behavior over time. The effect was dose dependent as measured for fluoxetine and Ampakines. The reduction of submissive behavior by Ampakines gradually faded after cessation of treatment and had a more rapid onset of activity (during the 1st week of treatment) than fluoxetine (after 2 weeks). The results suggest that Ampakines may have antidepressant activity. The potential of depression treatment with memory-enhancing drugs is hypothesized and the link between cognition and depression is discussed.     

Prostaglandin E2-induced arachidonic acid release and catecholamine secretion from cultured bovine adrenal chromaffin cells.

We recently reported that prostaglandin E2 (PGE2) and arachidonic acid (AA) each induced a gradual secretion of catecholamines from cultured bovine adrenal chromaffin cells in the presence of ouabain by stimulation of phosphoinositide metabolism. In the present study, we examined the relationship between phospholipase A2 and C activation and catecholamine secretion by PGE2 in chromaffin cells. The phospholipase A2 inhibitors p-bromophenacyl bromide and mepacrine did not affect the basal and ouabain-induced release, but dose-dependently blocked PGE2-evoked phosphoinositide metabolism and the consequent catecholamine release at an IC50 value of 3 microM. PGE2 induced rapid hydrolysis of [3H]AA from prelabeled phospholipid pools: the release of [3H]AA could be detected at as early as 15 sec and reached a plateau after 1 min. While the phospholipase C inhibitor neomycin did not inhibit PGE2-induced AA release, phospholipase A2 inhibitors dose-dependently inhibited it at IC50 values comparable to those for catecholamine release. Pretreatment of intact cells with the phorbol ester 12-O-tetradecanoylphorbol 13-acetate, but not with pertussis toxin, prevented AA release by PGE2. These results demonstrate that PGE2 activates phospholipase A2 as well as phospholipase C in a pertussis toxin-insensitive manner and suggest that the released arachidonic acid may be involved in PGE2-induced catecholamine release from chromaffin cells.     

Daidzin protects PC12 cells from serum deprivation-induced apoptosis

This article examines the effect of daidzin on PC12 cell apoptosis induced by serum-free medium. PC12 cell survival was measured by MTT assay. The DNA content and percentage of apoptosis were monitored by flow cytometry and DNA fragmentation was analyzed by agarose gel electrophoresis. The results showed that serum-free (12 h) medium induced apoptosis in PC12 cells. When the cells had been treated with daidzin (0.1, 1 μM) for 12 h, the percentage of PC12 cell apoptosis was significantly decreased to 12.21 and 4.24% from 91.94% in the group with serum deprivation, and DNA fragmentation was prevented. Daidzin (0.01-10 μM) attenuated the cytotoxic effect of sodium cyanide (20 mM), glutamate (0.5 mM) and sodium nitroprusside (0.5 mM) in a manner dependent on concentration. The results suggested that daidzin prevented PC12 cell from serum free-induced apoptosis.