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Tonon MC, Vaudry H, Chuquet J, Guillebaud F, Fan J, Masmoudi-Kouki O, Vaudry D, Lanfray D, Morin F, Prevot V, Papadopoulos V, Troadec JD, Leprince J. Endozepines and their receptors: Structure, functions and pathophysiological significance. Pharmacol Ther 2020; 208:107386. [DOI: 10.1016/j.pharmthera.2019.06.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 06/20/2019] [Indexed: 02/06/2023]
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Abela L, Kurian MA. Postsynaptic movement disorders: clinical phenotypes, genotypes, and disease mechanisms. J Inherit Metab Dis 2018; 41:1077-1091. [PMID: 29948482 PMCID: PMC6326993 DOI: 10.1007/s10545-018-0205-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 05/13/2018] [Accepted: 05/18/2018] [Indexed: 12/30/2022]
Abstract
Movement disorders comprise a group of heterogeneous diseases with often complex clinical phenotypes. Overlapping symptoms and a lack of diagnostic biomarkers may hamper making a definitive diagnosis. Next-generation sequencing techniques have substantially contributed to unraveling genetic etiologies underlying movement disorders and thereby improved diagnoses. Defects in dopaminergic signaling in postsynaptic striatal medium spiny neurons are emerging as a pathogenic mechanism in a number of newly identified hyperkinetic movement disorders. Several of the causative genes encode components of the cAMP pathway, a critical postsynaptic signaling pathway in medium spiny neurons. Here, we review the clinical presentation, genetic findings, and disease mechanisms that characterize these genetic postsynaptic movement disorders.
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Affiliation(s)
- Lucia Abela
- Molecular Neurosciences, Developmental Neuroscience, UCL Institute of Child Health, London, UK
| | - Manju A Kurian
- Molecular Neurosciences, Developmental Neuroscience, UCL Institute of Child Health, London, UK.
- Developmental Neurosciences Programme, UCL GOS - Institute of Child Health, 30 Guilford Street, London, WC1N 1EH, UK.
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Chang FCF, Westenberger A, Dale RC, Smith M, Pall HS, Perez-Dueñas B, Grattan-Smith P, Ouvrier RA, Mahant N, Hanna BC, Hunter M, Lawson JA, Max C, Sachdev R, Meyer E, Crimmins D, Pryor D, Morris JGL, Münchau A, Grozeva D, Carss KJ, Raymond L, Kurian MA, Klein C, Fung VSC. Phenotypic insights into ADCY5-associated disease. Mov Disord 2016; 31:1033-40. [PMID: 27061943 PMCID: PMC4950003 DOI: 10.1002/mds.26598] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 01/13/2016] [Accepted: 01/31/2016] [Indexed: 12/01/2022] Open
Abstract
Background Adenylyl cyclase 5 (ADCY5) mutations is associated with heterogenous syndromes: familial dyskinesia and facial myokymia; paroxysmal chorea and dystonia; autosomal‐dominant chorea and dystonia; and benign hereditary chorea. We provide detailed clinical data on 7 patients from six new kindreds with mutations in the ADCY5 gene, in order to expand and define the phenotypic spectrum of ADCY5 mutations. Methods In 5 of the 7 patients, followed over a period of 9 to 32 years, ADCY5 was sequenced by Sanger sequencing. The other 2 unrelated patients participated in studies for undiagnosed pediatric hyperkinetic movement disorders and underwent whole‐exome sequencing. Results Five patients had the previously reported p.R418W ADCY5 mutation; we also identified two novel mutations at p.R418G and p.R418Q. All patients presented with motor milestone delay, infantile‐onset action‐induced generalized choreoathetosis, dystonia, or myoclonus, with episodic exacerbations during drowsiness being a characteristic feature. Axial hypotonia, impaired upward saccades, and intellectual disability were variable features. The p.R418G and p.R418Q mutation patients had a milder phenotype. Six of seven patients had mild functional gain with clonazepam or clobazam. One patient had bilateral globus pallidal DBS at the age of 33 with marked reduction in dyskinesia, which resulted in mild functional improvement. Conclusion We further delineate the clinical features of ADCY5 gene mutations and illustrate its wide phenotypic expression. We describe mild improvement after treatment with clonazepam, clobazam, and bilateral pallidal DBS. ADCY5‐associated dyskinesia may be under‐recognized, and its diagnosis has important prognostic, genetic, and therapeutic implications. © 2016 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society
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Affiliation(s)
- Florence C F Chang
- Movement Disorders Unit, Department of Neurology, Westmead Hospital, Sydney, Australia
| | - Ana Westenberger
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Russell C Dale
- TY Nelson Department of Neurology and Neurosurgery, Children's Hospital at Westmead, Westmead, Australia.,University of Sydney, Sydney, Australia
| | - Martin Smith
- Department of Neurology, Birmingham Children's Hospital, Birmingham, United Kingdom
| | - Hardev S Pall
- College of Medical and Dental Studies, University of Birmingham, Birmingham, United Kingdom
| | - Belen Perez-Dueñas
- Molecular Neurosciences, Developmental Neurosciences Program, Institute of Child Health, University College London, London, United Kingdom.,Department of Child Neurology, Sant Joan de Déu Hospital, University of Barcelona, Spain
| | - Padraic Grattan-Smith
- TY Nelson Department of Neurology and Neurosurgery, Children's Hospital at Westmead, Westmead, Australia
| | - Robert A Ouvrier
- TY Nelson Department of Neurology and Neurosurgery, Children's Hospital at Westmead, Westmead, Australia
| | - Neil Mahant
- Sydney Medical School, University of Sydney, Australia
| | | | - Matthew Hunter
- Hunter Genetics, John Hunter Hospital, Newcastle, Australia.,Genetics of Learning Disability Service, Newcastle, Australia
| | - John A Lawson
- Sydney Children's Hospitals Network, Randwick, Australia
| | - Christoph Max
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Rani Sachdev
- Department of Medical Genetics, Sydney Children's Hospital, Randwick, Australia
| | - Esther Meyer
- Molecular Neurosciences, Developmental Neurosciences Program, Institute of Child Health, University College London, London, United Kingdom
| | | | - Donald Pryor
- Neurology Department, St George Hospital, Kogarah, Australia
| | - John G L Morris
- Movement Disorders Unit, Department of Neurology, Westmead Hospital, Sydney, Australia
| | - Alex Münchau
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Detelina Grozeva
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Keren J Carss
- Department of Haematology, University of Cambridge, NHS Blood and Transplant Center, Cambridge, United Kingdom.,Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom
| | - Lucy Raymond
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Manju A Kurian
- Molecular Neurosciences, Developmental Neurosciences Program, Institute of Child Health, University College London, London, United Kingdom
| | - Christine Klein
- Institute of Neurogenetics, University of Lübeck, Lübeck, Germany
| | - Victor S C Fung
- Movement Disorders Unit, Department of Neurology, Westmead Hospital, Sydney, Australia.,Sydney Medical School, University of Sydney, Australia
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Bunten H, Liang WJ, Pounder DJ, Seneviratne C, Osselton D. OPRM1 and CYP2B6 gene variants as risk factors in methadone-related deaths. Clin Pharmacol Ther 2010; 88:383-9. [PMID: 20668445 DOI: 10.1038/clpt.2010.127] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Methadone is a medication valued for its effectiveness in the treatment of heroin addiction; however, many fatal poisonings associated with its use have been reported over the years. We have examined the association between CYP2B6 and micro-opioid receptor (OPRM1) gene variations and apparent susceptibility to methadone poisoning. Genomic DNA was extracted from postmortem whole blood of 40 individuals whose deaths were attributed to methadone poisoning. The presence of CYP2B6*4,*9, and *6 alleles and the OPRM1 A118G variant was determined by SNP genotyping. CYP2B6 *4, *9, and *6 alleles were found to be associated with higher postmortem methadone concentrations in blood (P < or = 0.05). OPRM1 A118G was also associated with higher postmortem methadone concentrations in blood but not to a level of statistical significance (P = 0.39). In these methadone-related deaths, OPRM1 118GA was associated with higher postmortem benzodiazepine concentrations (P = 0.04), a finding not associated with morphine-related deaths. The risk of a methadone-related fatality during treatment may be evaluated in part by screening for CYP2B6*6 and A118G.
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Affiliation(s)
- H Bunten
- Centre for Forensic Sciences, Bournemouth University, Dorset, UK.
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Lintzeris N, Nielsen S. Benzodiazepines, Methadone and Buprenorphine: Interactions and Clinical Management. Am J Addict 2010; 19:59-72. [DOI: 10.1111/j.1521-0391.2009.00007.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Mégarbane B, Hreiche R, Pirnay S, Marie N, Baud FJ. Does high-dose buprenorphine cause respiratory depression?: possible mechanisms and therapeutic consequences. ACTA ACUST UNITED AC 2007; 25:79-85. [PMID: 16958555 DOI: 10.2165/00139709-200625020-00002] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Buprenorphine is an opioid agonist-antagonist with a 'ceiling effect' for respiratory depression. Compared with methadone, its unique pharmacology offers practical advantages and enhanced safety when prescribed as recommended and supervised by a physician. Buprenorphine has been approved in several countries as an efficient and safe maintenance therapy for heroin addiction. Its use resulted in a salutary effect with a reduction in heroin overdose-related deaths in countries that implemented office-based buprenorphine maintenance. In France, however, where high-dose buprenorphine has been marketed since 1996, several cases of asphyxic deaths were reported among addicts treated with buprenorphine. Death resulted from buprenorphine intravenous misuse or concomitant sedative drug ingestion, such as benzodiazepines. In these situations of abuse, misuse, or in association with elevated doses of psychotropic drugs, buprenorphine may cause severe respiratory depression. Unlike other opiates, the respiratory effects from buprenorphine are not responsive to naloxone. However, the exact mechanism of buprenorphine-induced effects on ventilation is still unknown. The role of norbuprenorphine, the main N-dealkylated buprenorphine metabolite with potent respiratory depressor activity, also remains unclear. Experimental studies investigating the respiratory effects of combinations of high doses of buprenorphine and benzodiazepines suggested that this drug-drug interaction may result from a pharmacodynamic interaction. A pharmacokinetic interaction between buprenorphine and flunitrazepam is also considered. As there are many questions regarding the possible dangers of death or respiratory depression associated with buprenorphine use, we aimed to present a comprehensive critical review of the published clinical and experimental studies on buprenorphine respiratory effects.
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Affiliation(s)
- Bruno Mégarbane
- INSERM U705, CNRS, UMR 7157, Université Paris 7, Université Paris 5, Hôpital Fernand Widal, Paris, France.
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Araki T, Matsubara M, Fujihara K, Kato H, Imai Y, Itoyama Y. Gamma-aminobutyric acidA and benzodiazepine receptor alterations in the rat brain after unilateral 6-hydroxydopamine lesions of the medial forebrain bundle. Neurol Res 2002; 24:107-12. [PMID: 11783749 DOI: 10.1179/016164102101199486] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Gamma-aminobutyric acidA (GABA(A)) and benzodiazepine (BZ) receptors and dopamine uptake sites in 6-hydroxydopamine-treated rat brains were studied by receptor autoradiography using [3H]muscimol, [3H]flunitrazepam and [3H]mazindol binding, respectively. The rats were unilaterally lesioned in the medial forebrain bundle and the brains were analyzed at 1, 2, 4 and 8 weeks post-lesion. Degeneration of the nigrostriatal pathway after 6-hydroxydopamine treatment caused a significant loss of dopamine uptake sites in the ipsilateral striatum and substantia nigra (SN) in the lesioned animals. In the contralateral side, however, dopamine uptake sites showed no significant changes in the brain throughout the experiments. On the other hand, no significant changes in GABA(A) receptors were observed in the brain of both the ipsilateral and contralateral sides during post-lesion. In contrast, BZ receptors were observed significantly increased in the ventromedial part of striatum of the ipsilateral side from 2 to 4 weeks post-lesion. Furthermore, a transient increase in BZ receptors was found in the ipsilateral SN only at 2 weeks post-lesion. In contralateral side, most regions examined showed no significant changes in BZ receptors throughout the experiments except for a transient increase in the SN at 1 week post-lesion. These results demonstrate that 6-hydroxydopamine can cause severe functional damage in dopamine uptake sites in the nigrostriatal pathway. Our results also suggest that the change in BZ receptors is more pronounced than that in GABA(A) receptors in the brain after 6-hydroxydopamine treatment. Furthermore, our findings suggest that the increase in BZ receptors in the brain of 6-hydroxydopamine-treated model may be due to the additional disruption of the nigrostriatal dopamine system. Thus, investigations into possible changes in neurotransmitter receptors other than dopaminergic receptors appear to be important for the elucidation of pathogenesis of Parkinsons disease.
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Affiliation(s)
- T Araki
- Department of Clinical Pharmacology and Therapeutics, Tohoku University Graduate School of Pharmaceutical Science and Medicine, Aoba-yama, Sendai, Japan.
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Niles LP, Wang J. Diazepam inhibits forskolin-stimulated adenylyl cyclase activity in human tumour cells. PHARMACOLOGY & TOXICOLOGY 1999; 85:153-6. [PMID: 10563512 DOI: 10.1111/j.1600-0773.1999.tb00084.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Previous studies have shown that the benzodiazepine agonist, diazepam, suppresses adenylyl cyclase activity in rat brain, via a G protein-coupled benzodiazepine receptor. Since diazepam binding sites are also present in diverse non-neuronal tissues including tumour cells, its effects on adenylyl cyclase activity were examined in membranes from human MCF-7 (breast cancer) and M-6 (melanoma) cells. Diazepam caused a biphasic and concentration-dependent inhibition of forskolin-stimulated adenylyl cyclase activity in MCF-7 membranes. The first phase of inhibition, at picomolar to nanomolar drug concentrations (EC50=5.7 x 10(-12)M), is similar to the receptor mediated phase observed in the rat brain. At micromolar concentrations of diazepam (EC50= 1.8 x 10(-4)M), the steep decrease in adenylyl cyclase activity may involve a direct action on the enzyme itself, as detected previously in rat brain membranes. Diazepam-induced suppression of adenylyl cyclase activity was also detected in M-6 membranes. However, in contrast to MCF-7 findings, only micromolar concentrations of diazepam (EC50=5.2 x 10(-4)M) inhibited enzyme activity in M-6 membranes. These findings suggest that G protein-coupled benzodiazepine receptors, which mediate inhibition of the adenylyl cyclase-cAMP pathway in the brain, are also expressed in MCF-7 cells.
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Affiliation(s)
- L P Niles
- McMaster University, Department of Biomedical Sciences, Hamilton, Ontario, Canada
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Tenn CC, Niles LP. Mechanisms underlying the antidopaminergic effect of clonazepam and melatonin in striatum. Neuropharmacology 1997; 36:1659-63. [PMID: 9517437 DOI: 10.1016/s0028-3908(97)00165-2] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Intrastriatal injection of the GABA(A) antagonist, bicuculline, caused about a 75% decrease in the inhibitory effect of the central-type benzodiazepine (BZ) agonist, clonazepam or the indoleamine hormone, melatonin, on apomorphine-induced rotation in a 6-hydroxydopamine model of dopaminergic supersensitivity. Pretreatment with the peripheral-type BZ antagonist, PK 11195 (intrastriatally or intraperitoneally), also attenuated the antidopaminergic effect of these drugs but with much less potency than bicuculline. However, the combination of both bicuculline and PK 11195, injected directly into the striatum, completely blocked the antidopaminergic action of clonazepam or melatonin. These results indicate that the antidopaminergic action of clonazepam and melatonin in the striatum involves two distinct mechanisms: (1) a predominant GABAergic activation via the BZ/GABA(A) receptor complex, and (2) a secondary mechanism linked to a PK 11195-sensitive BZ receptor pathway. Recent studies indicate that PK 11195 blocks BZ-induced inhibition of the adenylyl cyclase-cyclic AMP pathway in the striatum. Since cyclic AMP has been implicated in the rotational behaviour of 6-hydroxydopamine-lesioned animals, it is possible that the antidopaminergic action of clonazepam and melatonin also involves suppression of this second messenger.
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Affiliation(s)
- C C Tenn
- Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
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10
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Abstract
The benzodiazepine agonist, diazepam, inhibits cAMP production in the rat brain. Since cAMP influences c-fos activity, we examined the effects of diazepam on expression of this immediate early gene, as indicated by Western blot analysis. Intraperitoneal administration of diazepam increased Fos protein levels in the striatum, but not in the hippocampus. In contrast, pretreatment with diazepam blocked the potent inducing effect of amphetamine, in both brain regions. Similar induction and blockade effects were also observed for a 90 kDa Fos related antigen (Fra), in the striatum and hippocampus. The possible mechanisms underlying the modulatory effects of diazepam on c-fos expression in the brain are discussed.
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Affiliation(s)
- L P Niles
- Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
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Tenn CC, Neu JM, Niles LP. PK 11195 blockade of benzodiazepine-induced inhibition of forskolin-stimulated adenylate cyclase activity in the striatum. Br J Pharmacol 1996; 119:223-8. [PMID: 8886401 PMCID: PMC1915837 DOI: 10.1111/j.1476-5381.1996.tb15974.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
1. The effects of benzodiazepine receptor antagonists on the inhibition of forskolin-stimulated adenylate cyclase (AC) activity by various benzodiazepine (BZ) and indoleamine agonists in the rat striatum were investigated. 2. A biphasic inhibition of forskolin-stimulated AC activity by the peripheral-type agonist, Ro5-4864, and a multiphasic inhibition by the non-selective BZ, diazepam, was observed. One phase of AC inhibition is consistent with a Gi-coupled receptor-mediated action, whereas the other phases appear to involve a direct effect on the enzyme itself. 3. While the central-type antagonist, flumazenil, had no effect on the ability of Ro5-4864 to inhibit AC activity, the peripheral-type receptor ligand, PK 11195, abolished the first phase of inhibition. 4. PK 11195 and pertussis toxin were found to block the inhibitory effect of various BZs and the indoleamines, melatonin and 2-iodomelatonin, on induced AC activity. 5. Saturation binding studies, conducted at 30 degrees C with [3H]-diazepam revealed a single binding site in the rat striatum (KD = 19.3 +/- 0.80 nM) which significantly decreased in affinity in the presence of GTP (KD = 30.5 +/- 2.6 nM; P < 0.05). No significant change in Bmax was observed. 6. These findings indicate the presence of Gi-coupled BZ receptors in the rat striatum. Thus, suppression of cyclic AMP production may contribute to the diverse neuropharmacological effects of BZs, melatonin and related drugs.
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Affiliation(s)
- C C Tenn
- Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
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Sheu MJ, Sribanditmongkol P, Santosa DN, Tejwani GA. Inhibition of morphine tolerance and dependence by diazepam and its relation to cyclic AMP levels in discrete rat brain regions and spinal cord. Brain Res 1995; 675:31-7. [PMID: 7796144 DOI: 10.1016/0006-8993(95)00036-p] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Diazepam inhibits morphine tolerance and dependence and reverses a decrease in the met-enkephalin level in brain induced by morphine. In this study, we investigated whether inhibition of morphine-induced tolerance and dependence by diazepam involved a change in cyclic AMP levels in discrete rat brain regions and spinal cord. Male Sprague-Dawley rats were made tolerant and dependent by subcutaneous (s.c.) implantation of six morphine pellets (two pellets on the first day, and four on the second day). Diazepam (0.25 mg/kg b. wt) was injected once daily intraperitoneally (i.p.) for 5 days. Control rats were implanted with placebo pellets and injected once daily with saline or diazepam (i.p.). Tail-flick antinociception was measured 1 h after injections everyday. Animals were administered s.c. naloxone (10 mg/kg) to induce naloxone-precipitated withdrawal syndrome on the final day of the experiment (day 5), and the jumping behavior was observed for 30 min. Concomitant treatment with diazepam (0.25 mg/kg) significantly decreased the development of morphine tolerance and dependence. Diazepam (0.25 mg/kg) treated rats also showed a significant decrease in the jumping behavior compared to animals treated with morphine alone. Rats were sacrificed 2 h after the injection of saline or diazepam (0.25 mg/kg) on the fifth day. Cyclic AMP was estimated by RIA. In the control rats, the concentration of cyclic AMP in cortex was > hippocampus > cerebellum > hypothalamus > striatum > midbrain > pituitary > pons/medulla > spinal cord. There was no change in the concentration of cyclic AMP in any of the brain regions examined from morphine tolerant animals.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M J Sheu
- Department of Pharmacology, Ohio State University, College of Medicine, Columbus 43210-1239, USA
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13
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Niles LP, Hashemi FS. Pharmacological inhibition of forskolin-stimulated adenylate cyclase activity in rat brain by melatonin, its analogs, and diazepam. Biochem Pharmacol 1990; 40:2701-5. [PMID: 2260993 DOI: 10.1016/0006-2952(90)90590-h] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Preincubation of rat forebrain membranes for 30-60 min with micromolar concentrations of the pineal hormone, melatonin, significantly inhibited forskolin-stimulated adenylate cyclase (AC) activity. Melatonin had an EC25 (concentration which inhibited AC activity by 25%) of 600 microM and caused a maximal inhibitory effect of approximately 30% at a concentration of 1000 microM. A comparison of the effects of melatonin and its analogs, 6-chloromelatonin and 2-iodomelatonin, in the striatum revealed that these halogenated drugs were 2-3 times more potent than melatonin in inhibiting AC activity. The EC25 values were 611, 226 and 189 microM for melatonin, 6-chloromelatonin and 2-iodomelatonin respectively. The receptor antagonists phentolamine (alpha-adrenergic), propranolol (beta-adrenergic), and metergoline (serotonergic) did not block the effect of melatonin in forebrain membranes. The central-type benzodiazepine (BZ) antagonist, Ro 15-1788 (flumazenil), also failed to block the inhibitory effects of melatonin, and the benzodiazepines, diazepam and Ro 5-4864, on AC activity. Evidence that inhibition of adenylate cyclase activity may be involved in the prevention of seizures suggests that the reported anticonvulsant effect of large doses of melatonin may be due to this mechanism. The greater potency of the halogenated melatonin analogs in inhibiting AC suggests that further study of their potential usefulness as anticonvulsants would be worthwhile.
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Affiliation(s)
- L P Niles
- Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada
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Ziyadeh FN, Agus ZS. Benzodiazepines inhibit transport-related oxygen consumption in thick ascending limb. THE AMERICAN JOURNAL OF PHYSIOLOGY 1988; 255:C385-92. [PMID: 3421319 DOI: 10.1152/ajpcell.1988.255.3.c385] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Specific binding sites for benzodiazepines (BZD) have been identified in several nonneuronal tissues including the kidney where they are localized predominantly to the tubular epithelium of the thick ascending limb of Henle's loop (TALH). The physiological function of these nonneuronal (peripheral) BZD-binding sites is undefined, but it has been suggested that they may represent receptors for putative endogenous ligands that may modulate cell function. In the current study, we examined the in vitro effects of diazepam and Ro5-4864, a specific peripheral BZD-receptor agonist, on the oxygen consumption of medullary TALH tubule suspensions of rabbit kidney. Maximal inhibition of total oxygen consumption was achieved at a dose of 5 X 10(-4) M of either agent. On average, diazepam and Ro5-4864 reduced total oxygen consumption by 41 and 44%, respectively. The predominant inhibition was in the ouabain-sensitive component of oxygen consumption, which suggests that BZDs inhibit active sodium-chloride transport in the TALH. To assess whether this inhibition depends on sodium uptake, TALH tubules were pretreated with amphotericin B (2 X 10(-6) M) to enhance sodium uptake and stimulate basal oxygen consumption; subsequent addition of Ro5-4864 (5 X 10(-4) M) still reduced oxygen consumption to a residual value that was not different from that in TALH tubules treated with Ro5-4864 but without pretreatment with amphotericin B. This suggests that BZD inhibition of transport-related oxygen consumption is not caused by diminution of sodium uptake into cells and thus appears to be distinct from the effect of furosemide.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- F N Ziyadeh
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104
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