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Sun L, Chen Y, Hou C, Sun X, Wang Z, Li S, Lv M, Chen X. Neuroprotective effect of total glycosides from paeonies against neurotoxicity induced by strychnos alkaloids related to recovering the levels of neurotransmitters and neuroendocrine hormones in rat serum and brain. RSC Adv 2018; 8:29210-29219. [PMID: 35548016 PMCID: PMC9084482 DOI: 10.1039/c8ra05384g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2018] [Accepted: 08/09/2018] [Indexed: 01/13/2023] Open
Abstract
Semen Strychni, a classical traditional Chinese medicine, has been widely used for its anti-tumor, analgesic and anti-inflammatory angiogenesis effects. However, taking an overdose of Semen Strychni might result in extreme neurotoxicity. Strychnos alkaloids are the main toxic constituents of Semen Strychni. Total glycosides from paeonies are considered to have neuroprotective effects. In this study, twelve potential endogenous biomarkers in rat serum and brain were monitored to investigate the protective effect of total glycosides from the paeony against strychnos alkaloids-induced neurotoxicity. A sensitive liquid chromatography-tandem mass spectrometry method was developed and validated to monitor eight neurotransmitters including glutamate, γ-aminobutyric acid, acetylcholine serotonin, dopamine, norepinephrine, tryptophan and tyrosine. An enzyme-linked immunosorbent assay method was selected for determination of four neuroendocrine hormones including thyrotrophin-releasing hormone, corticotrophin-releasing hormone, antidiuretic hormone and prolactin. Results showed that continuous administration of strychnos alkaloids for 15 days caused significant changed levels of the biomarkers (especially the four neuroendocrine hormones). Meanwhile, total glycosides from paeony pretreated rats (administrated with total glycosides from the paeony for 15 days before exposure to strychnos alkaloids) showed recovered levels of these biomarkers. The results suggested that the neurotransmitters and neuroendocrine hormones in serum and brain might play potential roles as biomarkers. This study provides the possibility of alleviating the Semen Strychni-induced neurotoxicity in clinic by pre-protection with total glycosides from paeonies. Eight neurotransmitters and four neuroendocrine hormones in rat serum and brain were quantified to investigate the neuroprotective effect of total glycosides from paeony against neurotoxicity induced by strychnos alkaloids.![]()
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Affiliation(s)
- Linjia Sun
- School of Pharmacy, Shenyang Pharmaceutical University 103 Wenhua Road in Shenhe District Shenyang China 110016 +8602423986259
| | - Yu Chen
- School of Pharmacy, Shenyang Pharmaceutical University 103 Wenhua Road in Shenhe District Shenyang China 110016 +8602423986259
| | - Chenzhi Hou
- Department of Pharmaceutical Analysis, China Pharmaceutical University Nanjing China
| | - Xiaoyang Sun
- School of Pharmacy, Shenyang Pharmaceutical University 103 Wenhua Road in Shenhe District Shenyang China 110016 +8602423986259
| | - Zhipeng Wang
- School of Pharmacy, Shenyang Pharmaceutical University 103 Wenhua Road in Shenhe District Shenyang China 110016 +8602423986259
| | - Shujuan Li
- School of Pharmacy, Shenyang Pharmaceutical University 103 Wenhua Road in Shenhe District Shenyang China 110016 +8602423986259
| | - Mingming Lv
- School of Pharmacy, Shenyang Pharmaceutical University 103 Wenhua Road in Shenhe District Shenyang China 110016 +8602423986259
| | - Xiaohui Chen
- School of Pharmacy, Shenyang Pharmaceutical University 103 Wenhua Road in Shenhe District Shenyang China 110016 +8602423986259
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2
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Endogenous adenosine A1 receptor activation underlies the transient post-ischemic rhythmic delta EEG activity. Clin Neurophysiol 2010; 122:1117-26. [PMID: 20947418 DOI: 10.1016/j.clinph.2010.09.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 09/19/2010] [Accepted: 09/20/2010] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Emergence of slow EEG rhythms within the delta frequency band following an ischemic insult of the brain has long been considered a marker of irreversible anatomical damage. Here we investigated whether ischemic adenosine release and subsequent functional inhibition via the adenosine A(1) receptor (A(1)R) contributes to post-ischemic delta activity. METHODS Rats were subjected to episodes of non-injuring transient global cerebral ischemia (GCI) under chloral hydrate anesthesia. RESULTS We found that a GCI lasting only 10s was enough to induce a brief discharge of rhythmic delta activity (RDA) with a peak frequency just below 1 Hz quantified as an increase by twofold of the 0.5-1.5 Hz spectral power. This post-ischemic RDA did not occur following administration of the A(1)R antagonist 8-cyclopentyl-1,3-dipropylxanthine. Nevertheless, a similar RDA could be induced in rats not subjected to GCI, by systemic administration of the A(1)R agonist N(6)-cyclopentyladenosine. CONCLUSIONS Our data suggest that A(1)R activation at levels that occur following cerebral ischemia underlies the transient post-ischemic RDA. SIGNIFICANCE It is likely that the functional, thus potentially reversible, synaptic disconnection by A(1)R activation promotes slow oscillations in the cortical networks. This should be accounted for in the interpretation of early post-ischemic EEG delta activity.
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Ilie A, Ciocan D, Zagrean AM, Nita DA, Zagrean L, Moldovan M. Endogenous activation of adenosine A(1) receptors accelerates ischemic suppression of spontaneous electrocortical activity. J Neurophysiol 2006; 96:2809-14. [PMID: 16885523 DOI: 10.1152/jn.00466.2006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Cerebral ischemia induces a rapid suppression of spontaneous brain rhythms prior to major alterations in ionic homeostasis. It was found in vitro during ischemia that the rapidly formed adenosine, resulting from the intracellular breakdown of ATP, may inhibit synaptic transmission via the A(1) receptor subtype. The link between endogenous A(1) receptor activation during ischemia and the suppression of spontaneous electrocortical activity has not yet been established in the intact brain. The aim of this study was to investigate in vivo the effects of A(1) receptor antagonism by 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) on the time to electrocortical suppression during global cerebral ischemia. Adult male Wistar rats under chloral hydrate anesthesia were subjected to 1-min transient "four-vessel occlusion" ischemic episodes, separated by 20-min reperfusion. The rats were injected intraperitoneally with either 1.25 mg/kg DPCPX dissolved in 2 ml/kg dimethyl sulfoxide (DMSO) or the same volume of DMSO alone, 15 min before the third ischemic episode. Time to electrocortical suppression was estimated based on the decay of the root mean square of two-channel electrocorticographic recordings. During the first two ischemic episodes, electrocortical suppression appeared after approximately 12 s in both groups. After DMSO administration, ischemic suppression remained unchanged. After DPCPX administration, the time to electrocortical suppression was increased by approximately 10 s, and bursts of activity were recorded during the entire ischemia. These effects disappeared within 15 h after DPCPX administration. Our data provide evidence that during cerebral ischemia endogenous activation of A(1) receptors accelerates the electrical "shut-down" of the whole brain.
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Affiliation(s)
- Andrei Ilie
- Center for Excellence in Neuroscience, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
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Youssef FF, Addae JI, Stone TW. LTP-induced depression of response to hypoxia in hippocampus: effects of adenosine receptor activation. Neuroreport 2003; 14:1809-14. [PMID: 14534425 DOI: 10.1097/00001756-200310060-00010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previous work has shown that long-term potentiation (LTP) can reduce the effects of hypoxia in depressing population spikes in rat hippocampal slices. We have now investigated the role of adenosine in this phenomenon. There is no mutual inhibition between the depressant effects of hypoxia and adenosine, but LTP reduces responses to both hypoxia and adenosine, as does application of an A1 receptor antagonist. The effect of LTP is not due to a change in the balance of activation of A1 and A2A adenosine receptors since a selective A2A receptor antagonist did not prevent the interaction. We suggest that LTP may reduce the response to hypoxia by attenuating neuronal sensitivity to adenosine A1 receptors.
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Affiliation(s)
- Farid F Youssef
- Department of Pre-Clinical Science, University of the West Indies, St Augustine Campus, Trinidad and Tobago.
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5
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Blood AB, Hunter CJ, Power GG. Adenosine mediates decreased cerebral metabolic rate and increased cerebral blood flow during acute moderate hypoxia in the near-term fetal sheep. J Physiol 2003; 553:935-45. [PMID: 14500776 PMCID: PMC2343626 DOI: 10.1113/jphysiol.2003.047928] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Exposure of the fetal sheep to moderate to severe hypoxic stress results in both increased cortical blood flow and decreased metabolic rate. Using intravenous infusion of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a selective adenosine A1 receptor antagonist that is permeable to the blood brain barrier, we examine the role of adenosine A1 receptors in mediating cortical blood flow and metabolic responses to moderate hypoxia. The effects of DPCPX blockade are compared to controls as well as animals receiving intravenous 8-(p-sulfophenyl)-theophylline) (8-SPT), a non-selective adenosine receptor antagonist which has been found to be blood brain barrier impermeable. Laser Doppler flow probes, tissue PO2, and thermocouples were implanted in the cerebral cortices of near-term fetal sheep. Catheters were placed in the brachial artery and sagittal sinus vein for collection of samples for blood gas analysis. Three to seven days later responses to a 30-min period of fetal hypoxemia (arterial PO2 10-12 mmHg) were studied with administration of 8-SPT, DPCPX, or vehicle. Cerebral metabolic rate was determined by calculation of both brain heat production and oxygen consumption. In response to hypoxia, control experiments demonstrated a 42 +/- 7 % decrease in cortical heat production and a 35 +/- 10 % reduction in oxygen consumption. In contrast, DPCPX infusion during hypoxia resulted in no significant change in brain heat production or oxygen consumption, suggesting the adenosine A1 receptor is involved in lowering metabolic rate during hypoxia. The decrease in cerebral metabolic rate was not altered by 8-SPT infusion, suggesting that the response is not mediated by adenosine receptors located outside the blood brain barrier. In response to hypoxia, control experiments demonstrated a 35 +/- 7 % increase in cortical blood flow. DPCPX infusion did not change this increase in cortical blood flow, however 8-SPT infusion attenuated increases in flow, indicating that hypoxic increases in cerebral blood flow are mediated by adenosine but not via the A1 receptor. In summary, adenosine appears to play a key role in fetal hypoxic defences, acting to increase O2 delivery via adenosine A2 receptors and to decrease metabolic rate via A1 receptors inside the blood brain barrier. These data show for the first time in the mammalian fetus that the adenosine A1 receptor is an important mediator of brain metabolic rate during moderate hypoxia.
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Affiliation(s)
- Arlin B Blood
- Center for Perinatal Biology, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA
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Hunter CJ, Bennet L, Power GG, Roelfsema V, Blood AB, Quaedackers JS, George S, Guan J, Gunn AJ. Key neuroprotective role for endogenous adenosine A1 receptor activation during asphyxia in the fetal sheep. Stroke 2003; 34:2240-5. [PMID: 12933964 DOI: 10.1161/01.str.0000083623.77327.ce] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE The fetus is well known to be able to survive prolonged exposure to asphyxia with minimal injury compared with older animals. We and others have observed a rapid suppression of EEG intensity with the onset of asphyxia, suggesting active inhibition that may be a major neuroprotective adaptation to asphyxia. Adenosine is a key regulator of cerebral metabolism in the fetus. METHODS We therefore tested the hypothesis that infusion of the specific adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), given before 10 minutes of profound asphyxia in near-term fetal sheep, would prevent neural inhibition and lead to increased brain damage. RESULTS DPCPX treatment was associated with a transient rise and delayed fall in EEG activity in response to cord occlusion (n=8) in contrast with a rapid and sustained suppression of EEG activity in controls (n=8). DPCPX was also associated with an earlier and greater increase in cortical impedance, reflecting earlier onset of primary cytotoxic edema, and a significantly smaller reduction in calculated cortical heat production after the start of cord occlusion. After reperfusion, DPCPX-treated fetuses but not controls developed delayed onset of seizures, which continued for 24 hours, and sustained greater selective hippocampal, striatal, and parasagittal neuronal loss after 72-hour recovery. CONCLUSIONS These data support the hypothesis that endogenous activation of the adenosine A1 receptor during severe asphyxia mediates the initial suppression of neural activity and is an important mechanism that protects the fetal brain.
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Affiliation(s)
- Christian J Hunter
- Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, Calif ., USA
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7
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Turner CP, Yan H, Schwartz M, Othman T, Rivkees SA. A1 adenosine receptor activation induces ventriculomegaly and white matter loss. Neuroreport 2002; 13:1199-204. [PMID: 12151769 DOI: 10.1097/00001756-200207020-00026] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A1 adenosine receptors (A1ARs) are widely expressed in the brain during development. To examine whether A1AR activation can alter postnatal brain formation, neonatal rats from postnatal days 3 to 14 were treated with the A1AR agonist N6-cyclopentyladenosine (CPA) in the presence or absence of the peripheral A1AR antagonist 8-(p-sulfophenyl)-theophylline (8SPT). CPA or CPA + 8SPT treatment resulted in reductions in white matter volume, ventriculomegaly, and neuronal loss. Quantitative electron microscopy revealed reductions in total axon volume following A1AR agonist treatment. We also observed reduced expression of myelin basic protein in treated animals. Showing that functional A1ARs were present over the ranges of ages studies, high levels of specific [3H]CCPA binding were observed at PD 4, 7 and 14, and receptor-G protein coupling was present at each age. These observations show that activation of A1ARs with doses of CPA that mimic the effects of high adenosine levels results in damage to the developing brain.
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Affiliation(s)
- Christopher P Turner
- Department of Pediatrics, P.O. 208081, Yale University School of Medicine, New Haven, CT 06520, USA
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8
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Dassesse D, Ledent C, Parmentier M, Schiffmann SN. Acute and chronic caffeine administration differentially alters striatal gene expression in wild-type and adenosine A(2A) receptor-deficient mice. Synapse 2001; 42:63-76. [PMID: 11574941 DOI: 10.1002/syn.1100] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In order to assess for the respective involvement of adenosine A(1) and A(2A) receptors (A(2A)-R) in the consequences of short- and long-term caffeine exposure on gene expression, the effects of acute caffeine administration on striatal, cortical, and hippocampal expression of immediate early genes (IEG), zif-268 and arc, and the effects of long-term caffeine or 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) exposure (once daily for 15 days) on striatal gene expression of substance P, enkephalin, and glutamic acid decarboxylase isoforms, GAD65 and GAD67, were evaluated in wild-type and A(2A)-R-deficient (A(2A)-R(-/-)) mice. In situ hybridization histochemistry was performed using oligonucleotides followed by quantitative image analysis. Our results demonstrated that a biphasic response of IEG expression to acute caffeine observed in the wild-type striatum was resumed in a monophasic response in the mutant striatum. In the cerebral cortex and hippocampus, the effect of caffeine was weak in wild-type, whereas in mutant mice it induced a 2-3-fold increase in the IEG expression to restore a level similar to the wild-type basal expression. Chronic caffeine and DPCPX-mediated regulation in neuropeptide and GADs striatal gene expression typically showed the mimicking of alterations resulting from the A(2A)-R genetic deficiency in 25 mg/kg caffeine-treated wild-type mice as well as the dose-dependent normalization of substance P and enkephalin expression in A(2A)-R(-/-) mice. These results indicate that, depending on the dose, the blockade of A(2A)-R or A(1) receptors by caffeine is preferentially revealed leading to highly differential alterations in striatal gene expression and they also suggested the central role of these two receptors on the control of dopaminergic functions.
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MESH Headings
- Animals
- Caffeine/pharmacology
- Cytoskeletal Proteins/genetics
- DNA-Binding Proteins/genetics
- Dose-Response Relationship, Drug
- Drug Administration Schedule
- Early Growth Response Protein 1
- Enkephalins/genetics
- Gene Expression Regulation/drug effects
- Gene Expression Regulation/physiology
- Genes, Immediate-Early/drug effects
- Genes, Immediate-Early/physiology
- Glutamate Decarboxylase/genetics
- Hippocampus/drug effects
- Hippocampus/metabolism
- Immediate-Early Proteins
- Isoenzymes/genetics
- Male
- Mice
- Mice, Knockout
- Neostriatum/drug effects
- Neostriatum/metabolism
- Nerve Tissue Proteins/genetics
- Neuropeptides/drug effects
- Neuropeptides/genetics
- Neuropeptides/metabolism
- Phosphodiesterase Inhibitors/pharmacology
- Purinergic P1 Receptor Antagonists
- RNA, Messenger/drug effects
- RNA, Messenger/metabolism
- Receptor, Adenosine A2A
- Receptors, Purinergic P1/deficiency
- Receptors, Purinergic P1/genetics
- Receptors, Purinergic P1/metabolism
- Somatosensory Cortex/drug effects
- Somatosensory Cortex/metabolism
- Substance P/genetics
- Transcription Factors/genetics
- Xanthines/pharmacology
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Affiliation(s)
- D Dassesse
- Laboratory of Neurophysiology, Department of Neuroscience, School of Medicine, Université Libre de Bruxelles, B-1070 Brussels, Belgium.
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Eschke D, Brand A, Scheibler P, Hess S, Eger K, Allgaier C, Nieber K. Effect of an adenosine A(1) receptor agonist and a novel pyrimidoindole on membrane properties and neurotransmitter release in rat cortical and hippocampal neurons. Neurochem Int 2001; 38:391-8. [PMID: 11222919 DOI: 10.1016/s0197-0186(00)00113-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Activation of adenosine A(1) receptors by endogenous adenosine plays a neuroprotective role under various pathophysiological conditions including hypoxia. Intracellular recordings were made in rat pyramidal cells of the somatosensory cortex. Hypoxia (5 min) induced a membrane depolarization and a decrease of input resistance. The A(1) receptor agonist N(6)-cyclopentyladenosine (CPA, 100 microM) reversibly inhibited the hypoxic depolarization. The inhibition was also present after blockade of the A(2A), A(2B) and A(3) receptor subtypes by selective antagonists. CPA had no effect on the hypoxic decrease of input resistance. 1,3-Dipropyl-8-cyclopentylxanthine (DPCPX), a selective A(1) receptor antagonist, which did not alter hypoxic depolarization when given alone abolished the inhibitory effect of CPA. Neither CPA nor DPCPX influenced membrane potential or apparent input resistance under normoxic conditions. The novel pyrimidoindole (R)-9-(1-methylbenzyl)-2-(4'-pyridyl)-9H-pyrimido[4,5-b]indole-4-amine (APPPI, 1 and 10 microM) reversibly diminished hypoxic depolarization but had no significant effect on input resistance. The effect of APPPI at a concentration of 1 microM, but not at 10 microM, was blocked by DPCPX (0.1 microM). CPA (100 microM) inhibited [(3)H]-noradrenaline ([(3)H]-NA) release from rat hippocampal brain slices significantly only in the presence of rauwolscine (0.1 microM), an alpha(2)-adrenoceptor antagonist. APPPI (1 and 10 microM) exhibited an inhibitory effect similar to that observed with CPA. The effects of both CPA and APPPI were antagonized by DPCPX (0.1 microM). The present data suggest that mainly presynaptic mechanisms prevent neurons from hypoxic changes by an inhibition of transmitter release. However, in contrast to CPA, APPPI exhibited additional effects, which require further investigation.
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Affiliation(s)
- D Eschke
- Institute of Pharmacy, University of Leipzig, Brüderstrasse 34, D-04103 Leipzig, Germany
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Sperlágh B, Zsilla G, Vizi ES. K(ATP) channel blockers selectively interact with A(1)-adenosine receptor mediated modulation of acetylcholine release in the rat hippocampus. Brain Res 2001; 889:63-70. [PMID: 11166687 DOI: 10.1016/s0006-8993(00)03110-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
In this study the role of ATP-sensitive K(+) channels (K(ATP) channels) in the A(1) receptor mediated presynaptic inhibitory modulation of acetylcholine release was investigated in the rat hippocampus. N(6)-Cyclohexyladenosine (CHA), the selective A(1)-adenosine receptor agonist, reduced concentration-dependently the stimulation-evoked (2 Hz, 1 ms, 240 shocks) [3H]acetylcholine ([3H]ACh) release, from in vitro superfused hippocampal slices preloaded with [3H]choline, an effect prevented by the selective A(1) receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). By themselves, neither K(ATP) channel openers, i.e. diazoxide, pinacidil and cromakalim, nor glibenclamide and glipizide, the inhibitors of K(ATP) channels, exerted a significant effect on the resting and evoked release of [3H]ACh. Glibenclamide and glipizide (10-100 microM) completely prevented the inhibitory effect of 0.1 microM CHA and shifted the concentration response curve of CHA to the right. 4-Aminopyridine (10-100 microM), the non-selective potassium channel blocker, increased the evoked release of [3H]ACh, but in the presence of 4-aminopyridine, the inhibitory effect of CHA (0.1 microM) still persisted. Oxotremorine, the M(2) muscarinic receptor agonist, decreased the stimulation-evoked release of [3H]ACh, but its effect was not reversed by glibenclamide. 1,3-Diethyl-8-phenylxanthine (DPX), the selective A(1)-antagonist, effectively displaced [3H]DPCPX in binding experiments, while in the case of glibenclamide and glipizide, only slight displacement was observed. In summary, our results suggest that K(ATP) channels are functionally coupled to A(1) receptors present on cholinergic terminals of the hippocampus, and glibenclamide and glipizide, by interacting with K(ATP) channels, relieve this inhibitory neuromodulation.
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Affiliation(s)
- B Sperlágh
- Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, POB 67, H-1450, Budapest, Hungary.
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Coelho JE, de Mendonça A, Ribeiro JA. Presynaptic inhibitory receptors mediate the depression of synaptic transmission upon hypoxia in rat hippocampal slices. Brain Res 2000; 869:158-65. [PMID: 10865070 DOI: 10.1016/s0006-8993(00)02381-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Hypoxia markedly depresses synaptic transmission in hippocampal slices of the rat. This depression is attributed to presynaptic inhibition of glutamate release and is largely mediated by adenosine released during hypoxia acting through presynaptic adenosine A(1) receptors. Paired pulse facilitation studies allowed us to confirm the presynaptic nature of the depression of synaptic transmission during hypoxia. We tested the hypothesis that activation of heterosynaptic inhibitory receptors localized in glutamatergic presynaptic terminals in the hippocampus, namely gamma-aminobutyric acid subtype B (GABA(B)) receptors, alpha(2)-adrenergic receptors, and muscarinic receptors might contribute to the hypoxia-induced depression of synaptic transmission. Field excitatory postsynaptic potentials were recorded in the CA1 area of hippocampal slices from young adult (5-6 weeks) Wistar rats. Neither the selective antagonist for alpha(2)-adrenergic receptors, rauwolscine (10 microM), nor the antagonist for the GABA(B) receptors, CGP 55845 (10 microM), modified the response to hypoxia. The selective adenosine A(1) receptor antagonist, DPCPX (50 nM), reduced the hypoxia-induced depression of synaptic transmission to 59.2+/-9.6%, and the muscarinic receptor antagonist, atropine (10 microM), in the presence of DPCPX (50 nM), further attenuated the depression of synaptic transmission to 49.4+/-8.0%. In the same experimental conditions, in the presence of DPCPX (50 nM), the muscarinic M(2) receptor antagonist AF-DX 116 (10 microM), but not the M(1) receptor antagonist pirenzepine (1 microM), also attenuated the hypoxia-induced depression to 41.6+/-6.6%. Activation of muscarinic M(2) receptors contributes to the depression of synaptic transmission upon hypoxia. This effect should assume particular relevance during prolonged periods of hypoxia when other mechanisms may become less efficient.
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MESH Headings
- Animals
- Excitatory Postsynaptic Potentials/physiology
- Glutamic Acid/metabolism
- Hippocampus/drug effects
- Hippocampus/pathology
- Hippocampus/physiopathology
- Hypoxia/pathology
- Hypoxia/physiopathology
- In Vitro Techniques
- Male
- Neural Inhibition/drug effects
- Neural Inhibition/physiology
- Neurons/drug effects
- Neurons/metabolism
- Neurons/pathology
- Presynaptic Terminals/drug effects
- Presynaptic Terminals/metabolism
- Presynaptic Terminals/ultrastructure
- Rats
- Rats, Wistar
- Receptor, Muscarinic M2
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, GABA-B/drug effects
- Receptors, GABA-B/metabolism
- Receptors, Muscarinic/drug effects
- Receptors, Muscarinic/metabolism
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
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Affiliation(s)
- J E Coelho
- Laboratory of Neurosciences, Faculty of Medicine of Lisbon, Av. Prof Egas Moniz, 1649-028, Lisbon, Portugal
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