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Walton SE, Krotulski AJ, Glatfelter GC, Walther D, Logan BK, Baumann MH. Plasma pharmacokinetics and pharmacodynamic effects of the 2-benzylbenzimidazole synthetic opioid, isotonitazene, in male rats. Psychopharmacology (Berl) 2023; 240:185-198. [PMID: 36526866 DOI: 10.1007/s00213-022-06292-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 11/29/2022] [Indexed: 12/23/2022]
Abstract
RATIONALE Isotonitazene is an illicit synthetic opioid associated with many intoxications and fatalities. Recent studies show that isotonitazene is a potent µ-opioid receptor (MOR) agonist in vitro, but little information is available about its in vivo effects. OBJECTIVES The aims of the present study were to investigate the pharmacokinetics of isotonitazene in rats, and relate pharmacokinetic parameters to pharmacodynamic effects. METHODS Isotonitazene and its metabolites were identified and quantified by liquid chromatography tandem quadrupole mass spectrometry (LC-QQQ-MS). Male Sprague-Dawley rats with jugular catheters and subcutaneous (s.c.) temperature transponders received isotonitazene (3, 10, 30 µg/kg, s.c.) or its vehicle. Blood samples were drawn at 15, 30, 60, 120, and 240 min post-injection, and plasma was assayed using LC-QQQ-MS. At each blood draw, body temperature, catalepsy scores, and hot plate latencies were recorded. RESULTS Maximum plasma concentrations of isotonitazene rose in parallel with increasing dose (range 0.2-9.8 ng/mL) and half-life ranged from 23.4 to 63.3 min. The metabolites 4'-hydroxy nitazene and N-desethyl isotonitazene were detected, and plasma concentrations were below the limit of quantitation (0.5 ng/mL) but above the limit of detection (0.1 ng/mL). Isotonitazene produced antinociception (ED50 = 4.22 µg/kg), catalepsy-like symptoms (ED50 = 8.68 µg/kg), and hypothermia (only at 30 µg/kg) that were significantly correlated with concentrations of isotonitazene. Radioligand binding in rat brain tissue revealed that isotonitazene displays nM affinity for MOR (Ki = 15.8 nM), while the N-desethyl metabolite shows even greater affinity (Ki = 2.2 nM). CONCLUSIONS In summary, isotonitazene is a potent MOR agonist whose pharmacodynamic effects are related to circulating concentrations of the parent drug. The high potency of isotonitazene portends substantial risk to users who are exposed to the drug.
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Affiliation(s)
- Sara E Walton
- Center for Forensic Science Research and Education, Fredric Rieders Family Foundation, 2300 Stratford Avenue, Willow Grove, PA, 19090, USA
- College of Life Sciences, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA, 19107, USA
| | - Alex J Krotulski
- Center for Forensic Science Research and Education, Fredric Rieders Family Foundation, 2300 Stratford Avenue, Willow Grove, PA, 19090, USA.
- College of Life Sciences, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA, 19107, USA.
| | - Grant C Glatfelter
- Designer Drug Research Unit, Intramural Research Program (IRP), National Institute On Drug Abuse (NIDA), National Institutes of Health, 333 Cassell Drive, Suite 4400, Baltimore, MD, 21224, USA
| | - Donna Walther
- Designer Drug Research Unit, Intramural Research Program (IRP), National Institute On Drug Abuse (NIDA), National Institutes of Health, 333 Cassell Drive, Suite 4400, Baltimore, MD, 21224, USA
| | - Barry K Logan
- Center for Forensic Science Research and Education, Fredric Rieders Family Foundation, 2300 Stratford Avenue, Willow Grove, PA, 19090, USA
- College of Life Sciences, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA, 19107, USA
- NMS Labs, 200 Welsh Road, Horsham, PA, 19044, USA
| | - Michael H Baumann
- Designer Drug Research Unit, Intramural Research Program (IRP), National Institute On Drug Abuse (NIDA), National Institutes of Health, 333 Cassell Drive, Suite 4400, Baltimore, MD, 21224, USA
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El Jordi O, Fischer KD, Meyer TB, Atwood BK, Oblak AL, Pan RW, McKinzie DL. Microglial knockdown does not affect acute withdrawal but delays analgesic tolerance from oxycodone in male and female C57BL/6J mice. ADVANCES IN DRUG AND ALCOHOL RESEARCH 2022; 2:10848. [PMID: 38390615 PMCID: PMC10880796 DOI: 10.3389/adar.2022.10848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 12/05/2022] [Indexed: 02/24/2024]
Abstract
Opioid Use Disorder (OUD) affects approximately 8%-12% of the population. In dependent individuals, abrupt cessation of opioid taking results in adverse withdrawal symptoms that reinforce drug taking behavior. Considerable unmet clinical need exists for new pharmacotherapies to treat opioid withdrawal as well as improve long-term abstinence. The neuroimmune system has received much scientific attention in recent years as a potential therapeutic target to combat various neurodegenerative and psychiatric disorders including addiction. However, the specific contribution of microglia has not been investigated in oxycodone dependence. Chronic daily treatment with the CSF1R inhibitor Pexidartinib (PLX3397) was administered to knockdown microglia expression and evaluate consequences on analgesia and on naloxone induced withdrawal from oxycodone. In vivo results indicated that an approximately 40% reduction in brain IBA1 staining was achieved in the PLX treatment group, which was associated with a delay in the development of analgesic tolerance to oxycodone and maintained antinociceptive efficacy. Acute withdrawal behavioral symptoms, brain astrocyte expression, and levels of many neuroinflammatory markers were not affected by PLX treatment. KC/GRO (also known as CXCL1) was significantly enhanced in the somatosensory cortex in oxycodone-treated mice receiving PLX. Microglial knock-down did not affect the expression of naloxoneinduced opioid withdrawal but affected antinociceptive responsivity. The consequences of increased KC/GRO expression within the somatosensory cortex due to microglial reduction during opioid dependence are unclear but may be important for neural pathways mediating opioid-induced analgesia.
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Affiliation(s)
- Omar El Jordi
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, United States
| | - Kathryn D Fischer
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, United States
| | - Timothy B Meyer
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, United States
| | - Brady K Atwood
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, United States
| | - Adrian L Oblak
- Department of Radiology and Imaging Sciences, Indiana University, Indianapolis, IN, United States
| | - Raymond W Pan
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, United States
| | - David L McKinzie
- Department of Pharmacology and Toxicology, Indiana University, Indianapolis, IN, United States
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Neuroprotective Effects of Pharmacological Hypothermia on Hyperglycolysis and Gluconeogenesis in Rats after Ischemic Stroke. Biomolecules 2022; 12:biom12060851. [PMID: 35740974 PMCID: PMC9220898 DOI: 10.3390/biom12060851] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 06/13/2022] [Accepted: 06/15/2022] [Indexed: 12/26/2022] Open
Abstract
Stroke is a leading threat to human life. Metabolic dysfunction of glucose may play a key role in stroke pathophysiology. Pharmacological hypothermia (PH) is a potential neuroprotective strategy for stroke, in which the temperature is decreased safely. The present study determined whether neuroprotective PH with chlorpromazine and promethazine (C + P), plus dihydrocapsaicin (DHC) improved glucose metabolism in acute ischemic stroke. A total of 208 adult male Sprague Dawley rats were randomly divided into the following groups: sham, stroke, and stroke with various treatments including C + P, DHC, C + P + DHC, phloretin (glucose transporter (GLUT)-1 inhibitor), cytochalasin B (GLUT-3 inhibitor), TZD (thiazolidinedione, phosphoenolpyruvate carboxykinase (PCK) inhibitor), and apocynin (nicotinamide adenine dinucleotide phosphate oxidase (NOX) inhibitor). Stroke was induced by middle cerebral artery occlusion (MCAO) for 2 h followed by 6 or 24 h of reperfusion. Rectal temperature was monitored before, during, and after PH. Infarct volume and neurological deficits were measured to assess the neuroprotective effects. Reactive oxygen species (ROS), NOX activity, lactate, apoptotic cell death, glucose, and ATP levels were measured. Protein expression of GLUT-1, GLUT-3, phosphofructokinase (PFK), lactate dehydrogenase (LDH), PCK1, PCK2, and NOX subunit gp91 was measured with Western blotting. PH with a combination of C + P and DHC induced faster, longer, and deeper hypothermia, as compared to each alone. PH significantly improved every measured outcome as compared to stroke and monotherapy. PH reduced brain infarction, neurological deficits, protein levels of glycolytic enzymes (GLUT-1, GLUT-3, PFK and LDH), gluconeogenic enzymes (PCK1 and PCK2), NOX activity and its subunit gp91, ROS, apoptotic cell death, glucose, and lactate, while raising ATP levels. In conclusion, stroke impaired glucose metabolism by enhancing hyperglycolysis and gluconeogenesis, which led to ischemic injury, all of which were reversed by PH induced by a combination of C + P and DHC.
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Ambler M, Hitrec T, Pickering A. Turn it off and on again: characteristics and control of torpor. Wellcome Open Res 2022; 6:313. [PMID: 35087956 PMCID: PMC8764563 DOI: 10.12688/wellcomeopenres.17379.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2022] [Indexed: 11/20/2022] Open
Abstract
Torpor is a hypothermic, hypoactive, hypometabolic state entered into by a wide range of animals in response to environmental challenge. This review summarises the current understanding of torpor. We start by describing the characteristics of the wide-ranging physiological adaptations associated with torpor. Next follows a discussion of thermoregulation, control of food intake and energy expenditure, and the interactions of sleep and thermoregulation, with particular emphasis on how those processes pertain to torpor. We move on to review the evidence for the systems that control torpor entry, including both the efferent circulating factors that signal the need for torpor, and the central processes that orchestrate it. Finally, we consider how the putative circuits responsible for torpor induction integrate with the established understanding of thermoregulation under non-torpid conditions and highlight important areas of uncertainty for future studies.
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Affiliation(s)
- Michael Ambler
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
| | - Timna Hitrec
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
| | - Anthony Pickering
- School of Physiology, Pharmacology, & Neuroscience, University of Bristol, Bristol, Bristol, BS8 1TD, UK
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Ambler M, Hitrec T, Pickering A. Turn it off and on again: characteristics and control of torpor. Wellcome Open Res 2021; 6:313. [DOI: 10.12688/wellcomeopenres.17379.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2021] [Indexed: 11/20/2022] Open
Abstract
Torpor is a hypothermic, hypoactive, hypometabolic state entered into by a wide range of animals in response to environmental challenge. This review summarises the current understanding of torpor. We start by describing the characteristics of the wide-ranging physiological adaptations associated with torpor. Next follows a discussion of thermoregulation, control of food intake and energy expenditure, and the interactions of sleep and thermoregulation, with particular emphasis on how those processes pertain to torpor. We move on to take a critical view of the evidence for the systems that control torpor entry, including both the efferent circulating factors that signal the need for torpor, and the central processes that orchestrate it. Finally, we consider how the putative circuits responsible for torpor induction integrate with the established understanding of thermoregulation under non-torpid conditions and highlight important areas of uncertainty for future studies.
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Monroe SC, Radke AK. Aversion-resistant fentanyl self-administration in mice. Psychopharmacology (Berl) 2021; 238:699-710. [PMID: 33226446 PMCID: PMC7914171 DOI: 10.1007/s00213-020-05722-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 11/13/2020] [Indexed: 12/28/2022]
Abstract
RATIONALE Animal models of compulsive drug use that continues despite negative consequences can be used to investigate the neural mechanisms of addiction. However, models of punished or aversion-resistant opioid self-administration are notably lacking. OBJECTIVES We sought to develop an aversion-resistant, oral fentanyl self-administration paradigm. METHODS In Experiment 1, C57BL/6J male and female, adult mice consumed fentanyl (10 μg/mL) in a two-bottle drinking in the dark task and escalating concentrations of quinine were added to the bottles. In Experiment 2, mice were trained to administer oral fentanyl (10 μg/mL) in an operant response task. Quinine was next added to the fentanyl solution in escalating concentrations. In Experiment 3, mice were trained to respond for oral fentanyl or fentanyl adulterated with 500 μM quinine on every session. In Experiment 4, mice were trained to respond for a 1% sucrose solution before introduction of quinine. RESULTS Quinine reduced two-bottle choice consumption in males but not in females. Both sexes demonstrated the ability to detect the selected concentrations of quinine in fentanyl. In the operant chamber, mice responded robustly for oral fentanyl but introduction of quinine at any stage of training was insufficient to reduce responding. In contrast, quinine reduced responding for sucrose at concentrations above 250 μM. CONCLUSIONS Mice will respond for and consume oral fentanyl in both a two-bottle choice and an operant response task. Quinine is detectable in fentanyl but mice will continue to respond for and consume fentanyl with quinine in both paradigms. These data support the use of these models in behavioral studies of compulsive-like opioid use.
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Affiliation(s)
| | - Anna K. Radke
- Correspondence to: Anna K. Radke, PhD, 90 N Patterson Ave, Oxford, OH, USA 45056,
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Pharmacokinetics and pharmacodynamics of cyclopropylfentanyl in male rats. Psychopharmacology (Berl) 2021; 238:3629-3641. [PMID: 34613431 PMCID: PMC8629808 DOI: 10.1007/s00213-021-05981-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 09/06/2021] [Indexed: 01/29/2023]
Abstract
BACKGROUND Illicitly manufactured fentanyl and its analogs are a major driving force behind the ongoing opioid crisis. Cyclopropylfentanyl is a fentanyl analog associated with many overdose deaths, but limited knowledge is available about its pharmacology. In the present study, we developed a bioanalytical method for the determination of cyclopropylfentanyl and its main metabolite cyclopropylnorfentanyl and evaluated pharmacokinetic-pharmacodynamic relationships in rats. METHOD An ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for determination of cyclopropylfentanyl and cyclopropylnorfentanyl in rat plasma. Male Sprague-Dawley rats fitted with jugular catheters and temperature transponders received cyclopropylfentanyl (30, 100, and 300 μg/kg) or saline subcutaneously. Blood specimens were withdrawn over an 8-h time period, along with measurements of pharmacodynamic endpoints. RESULTS The analytical method was validated, and both analytes exhibited a low limit of quantification (15 pg/mL). Cyclopropylfentanyl caused dose-related increases in hot plate latency (ED50 = 48 µg/kg) and catalepsy (ED50 = 87 µg/kg) and produced long-lasting hypothermia at the highest dose. Plasma cyclopropylfentanyl rose rapidly in a dose-related fashion, reaching maximal concentration (Cmax) after 15-28 min, whereas metabolite Cmax occurred later at 45-90 min. Cyclopropylfentanyl Cmax values were similar to concentrations measured in non-fatal intoxications in humans; however, differences in parent drug: metabolite ratio indicated possible interspecies variance in metabolism. CONCLUSION Our study shows that cyclopropylfentanyl produces typical opioid-like effects in male rats. Cyclopropylfentanyl displays much greater analgesic potency when compared to morphine, suggesting that cyclopropylfentanyl poses increased overdose risk for unsuspecting users.
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Truver MT, Smith CR, Garibay N, Kopajtic TA, Swortwood MJ, Baumann MH. Pharmacodynamics and pharmacokinetics of the novel synthetic opioid, U-47700, in male rats. Neuropharmacology 2020; 177:108195. [PMID: 32533977 DOI: 10.1016/j.neuropharm.2020.108195] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 06/03/2020] [Accepted: 06/08/2020] [Indexed: 02/01/2023]
Abstract
Novel synthetic opioids are appearing in recreational drug markets worldwide as adulterants in heroin or ingredients in counterfeit analgesic medications. Trans-3,4-dichloro-N-[2-(dimethylamino)cyclohexyl]-N-methyl-benzamide (U-47700) is an example of a non-fentanyl synthetic opioid linked to overdose deaths. Here, we examined the pharmacodynamics and pharmacokinetics of U-47700 in rats. Male Sprague-Dawley rats were fitted with intravenous (i.v.) catheters and subcutaneous (s.c.) temperature transponders under ketamine/xylazine anesthesia. One week later, rats received s.c. injections of U-47700 HCl (0.3, 1.0 or 3.0 mg/kg) or saline, and blood samples (0.3 mL) were withdrawn via i.v. catheters at 15, 30, 60, 120, 240, 480 min post-injection. Pharmacodynamic effects were assessed at each blood withdrawal, and plasma was assayed for U-47700 and its metabolites by liquid chromatography tandem mass spectrometry. U-47700 induced dose-related increases in hot plate latency (ED50 = 0.5 mg/kg) and catalepsy (ED50 = 1.7 mg/kg), while the 3.0 mg/kg dose also caused hypothermia. Plasma levels of U-47700 rose linearly as dose increased, with maximal concentration (Cmax) achieved by 15-38 min. Cmax values for N-desmethyl-U-47700 and N,N-didesmethyl-U-47700 were delayed but reached levels in the same range as the parent compound. Pharmacodynamic effects were correlated with plasma U-47700 and its N-desmethyl metabolite. Using radioligand binding assays, U-47700 displayed high affinity for μ-opioid receptors (Ki = 11.1 nM) whereas metabolites were more than 18-fold weaker. Our data reveal that U-47700 induces typical μ-opioid effects which are related to plasma concentrations of the parent compound. Given its high potency, U-47700 poses substantial risk to humans who are inadvertently exposed to the drug.
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Affiliation(s)
- Michael T Truver
- Department of Forensic Science, College of Criminal Justice, Sam Houston State University, Huntsville, TX, USA
| | - Christina R Smith
- Department of Forensic Science, College of Criminal Justice, Sam Houston State University, Huntsville, TX, USA
| | - Nancy Garibay
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Theresa A Kopajtic
- Biobehavioral Imaging and Molecular Neuropsychopharmacology Unit, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Madeleine J Swortwood
- Department of Forensic Science, College of Criminal Justice, Sam Houston State University, Huntsville, TX, USA.
| | - Michael H Baumann
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA.
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Activation of Kappa Opioid Receptor Regulates the Hypothermic Response to Calorie Restriction and Limits Body Weight Loss. Curr Biol 2019; 29:4291-4299.e4. [PMID: 31786059 DOI: 10.1016/j.cub.2019.10.027] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 09/16/2019] [Accepted: 10/16/2019] [Indexed: 12/24/2022]
Abstract
Mammals maintain a nearly constant core body temperature (Tb) by balancing heat production and heat dissipation. This comes at a high metabolic cost that is sustainable if adequate calorie intake is maintained. When nutrients are scarce or experimentally reduced such as during calorie restriction (CR), endotherms can reduce energy expenditure by lowering Tb [1-6]. This adaptive response conserves energy, limiting the loss of body weight due to low calorie intake [7-10]. Here we show that this response is regulated by the kappa opioid receptor (KOR). CR is associated with increased hypothalamic levels of the endogenous opioid Leu-enkephalin, which is derived from the KOR agonist precursor dynorphin [11]. Pharmacological inhibition of KOR, but not of the delta or the mu opioid receptor subtypes, fully blocked CR-induced hypothermia and increased weight loss during CR independent of calorie intake. Similar results were seen with DIO mice subjected to CR. In contrast, inhibiting KOR did not change Tb in animals fed ad libitum (AL). Chemogenetic inhibition of KOR neurons in the hypothalamic preoptic area reduced the CR-induced hypothermia, whereas chemogenetic activation of prodynorphin-expressing neurons in the arcuate or the parabrachial nucleus lowered Tb. These data indicate that KOR signaling is a pivotal regulator of energy homeostasis and can affect body weight during dieting by modulating Tb and energy expenditure.
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Evidence for nonlinear accumulation of the ultrapotent fentanyl analog, carfentanil, after systemic administration to male rats. Neuropharmacology 2019; 158:107596. [PMID: 30965021 DOI: 10.1016/j.neuropharm.2019.04.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 04/03/2019] [Accepted: 04/03/2019] [Indexed: 11/21/2022]
Abstract
The current opioid overdose crisis is being exacerbated by illicitly manufactured fentanyl and its analogs. Carfentanil is a fentanyl analog that is 10,000-times more potent than morphine, but limited information is available about its pharmacology. The present study had two aims: 1) to validate a method for quantifying carfentanil and its metabolite norcarfentanil in small-volume samples, and 2) to use the method for examining pharmacodynamic-pharmacokinetic relationships in rats. The analytical method involved liquid-liquid extraction of plasma samples followed by quantitation of carfentanil and norcarfentanil using ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). The method was validated following SWGTOX guidelines, and both analytes displayed limits of detection and quantification at 7.5 and 15 pg/mL, respectively. Male Sprague-Dawley rats fitted with jugular catheters and temperature transponders received subcutaneous carfentanil (1, 3 and 10 μg/kg) or saline. Repeated blood specimens were obtained over 8 h, along with pharmacodynamic measures including core temperature and catalepsy scores. Carfentanil produced dose-related hypothermia and catalepsy that lasted up to 8 h. Carfentanil Cmax occurred at 15 min whereas metabolite Cmax was at 1-2 h. Concentrations of both analytes increased in a dose-related fashion, but area-under-the-curve values were much greater than predicted after 10 μg/kg. Plasma half-life for carfentanil increased at higher doses. Our findings reveal that carfentanil produces marked hypothermia and catalepsy, which is accompanied by nonlinear accumulation of the drug at high doses. We hypothesize that impaired clearance of carfentanil in humans could contribute to life-threatening effects of this ultrapotent opioid agonist. This article is part of the Special Issue entitled 'New Vistas in Opioid Pharmacology'.
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δ-Opioid Receptor-Nrf-2-Mediated Inhibition of Inflammatory Cytokines in Neonatal Hypoxic-Ischemic Encephalopathy. Mol Neurobiol 2018; 56:5229-5240. [PMID: 30560518 DOI: 10.1007/s12035-018-1452-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 12/07/2018] [Indexed: 12/11/2022]
Abstract
Neonatal hypoxic-ischemic encephalopathy (HIE) causes serious neurological disability; there are, however, currently few promising therapies for it. We have recently shown that δ-opioid receptor (DOR) is neuroprotective by downregulating TNF-α. Since hypoxia-ischemia (HI) triggers a robust inflammatory response, which exacerbates HI brain damage, we investigated, in this study, whether DOR activation could regulate inflammatory cytokine expression, thereby playing a protective effect on the neonatal brain under HI. Twenty-five neonatal rats were randomly divided into five groups: (1) control (control); (2) HI; (3) HI with saline (HI + NS); (4) DOR activation with UFP-512 (a potent and specific DOR agonist) under HI conditions (HI + U); and (5) DOR inhibition using NT treatment under HI conditions (HI + NT). The rats were sacrificed by decapitation at 24 h after HI, and their brains were rapidly removed for measurements. The protein expression of TNF-α, IL-6, ICAM-1, IL-10, IL-18, NQO-1, Nrf-2, and HO-1 was measured using Western blot. In the hemispheres exposed to HI, DOR activation significantly decreased the expressions of TNF-α, IL-6, and ICAM-1 in the cortex, while it significantly increased IL-10 and had no effect on IL-18 in the same region. In contrast, DOR had no appreciable effect on inflammatory cytokine expression in non-cortical tissues including hippocampal, subcortical, and cerebellar tissues. Moreover, HI stress triggered an upregulation of Nrf-2 nuclear protein as well as some of its downstream anti-inflammatory genes such as HO-1 and NQO-1 in the cortex, while DOR activation further augmented such a protective reaction against HI injury. DOR plays an important role in protecting against HI by regulating the expression of inflammatory and anti-inflammatory cytokines in the cortex, which is likely mediated by the Nrf-2/HO-1/NQO-1 signaling.
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Schindler CW, Gramling BR, Justinova Z, Thorndike EB, Baumann MH. Synthetic cannabinoids found in "spice" products alter body temperature and cardiovascular parameters in conscious male rats. Drug Alcohol Depend 2017; 179:387-394. [PMID: 28846955 PMCID: PMC5599362 DOI: 10.1016/j.drugalcdep.2017.07.029] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 06/16/2017] [Accepted: 07/25/2017] [Indexed: 01/30/2023]
Abstract
BACKGROUND The misuse of synthetic cannabinoids is a persistent public health concern. Because these drugs target the same cannabinoid receptors as the active ingredient of marijuana, Δ9-tetrahydrocannabinol (THC), we compared the effects of synthetic cannabinoids and THC on body temperature and cardiovascular parameters. METHODS Biotelemetry transmitters for the measurement of body temperature or blood pressure (BP) were surgically implanted into separate groups of male rats. THC and the synthetic cannabinoids CP55,940, JWH-018, AM2201 and XLR-11 were injected s.c., and rats were placed into isolation cubicles for 3h. RESULTS THC and synthetic cannabinoids produced dose-related decreases in body temperature that were most prominent in the final 2h of the session. The rank order of potency was CP55,940>AM2201=JWH-018>THC=XLR-11. The cannabinoid inverse agonist rimonabant antagonized the hypothermic effect of all compounds. Synthetic cannabinoids elevated BP in comparison to vehicle treatment during the first h of the session, while heart rate was unaffected. The rank order of potency for BP increases was similar to that seen for hypothermia. Hypertensive effects of CP55,940 and JWH-018 were not antagonized by rimonabant or the neutral antagonist AM4113. However, the BP responses to both drugs were antagonized by pretreatment with either the ganglionic blocker hexamethonium or the α1 adrenergic antagonist prazosin. CONCLUSIONS Our results show that synthetic cannabinoids produce hypothermia in rats by a mechanism involving cannabinoid receptors, while they increase BP by a mechanism independent of these sites. The hypertensive effect appears to involve central sympathetic outflow.
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Affiliation(s)
- Charles W. Schindler
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD,Preclinical Pharmacology Section, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD
| | - Benjamin R. Gramling
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD
| | - Zuzana Justinova
- Preclinical Pharmacology Section, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD
| | - Eric B. Thorndike
- Preclinical Pharmacology Section, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD
| | - Michael H. Baumann
- Designer Drug Research Unit, Intramural Research Program, National Institute on Drug Abuse, Baltimore, MD
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Shevelev OB, Illarionova NB, Petrovski DV, Sarapultsev AP, Chupakhin ON, Moshkin MP. Effects of a compound from the group of substituted thiadiazines with hypothermia inducing properties on brain metabolism in rats, a study in vivo and in vitro. PLoS One 2017; 12:e0180739. [PMID: 28678857 PMCID: PMC5498073 DOI: 10.1371/journal.pone.0180739] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 06/20/2017] [Indexed: 02/06/2023] Open
Abstract
The aim of the present study was to examine how administration of a compound of 1,3,4- thiadiazine class 2-morpholino-5-phenyl-6H-1,3,4-thiadiazine, hydrobromide (L-17) with hypothermia inducing properties affects the brain metabolism. The mechanism by which L-17 induces hypothermia is unknown; it may involve hypothalamic central thermoregulation as well as act via inhibition of energy metabolism. We tested the hypothesis that L-17 may induce hypothermia by directly inhibiting energy metabolism. The study in vivo was carried out on Sprague-Dawley adult rats. Two doses of L-17 were administered (190 mg/kg and 760 mg/kg). Brain metabolites were analyzed in control and treated groups using magnetic resonance spectroscopy, along with blood flow rate measurements in carotid arteries and body temperature measurements. Further in vitro studies on primary cultures from rat hippocampus were carried out to perform a mitochondria function test of L-17 pre-incubation (100 μM, 30 min). Analysis of brain metabolites showed no significant changes in 190 mg/kg treated group along with a significant reduction in body temperature by 1.5°C. However, administration of L-17 in higher dose 760 mg/kg provoked changes in brain metabolites indicative of neurotoxicity as well as reduction in carotid arteries flow rate. In addition, a balance change of excitatory and inhibitory neurotransmitters was observed. The L-17 pre-incubation with cell primary cultures from rat brain showed no significant changes in mitochondrial function. The results obtained in the study indicate that acute administration of L-17 190 mg/kg in rats induces mild hypothermia with no adverse effects onto brain metabolism.
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Affiliation(s)
- O. B. Shevelev
- The federal research center Institute of Cytology and Genetics Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
- * E-mail:
| | - N. B. Illarionova
- The federal research center Institute of Cytology and Genetics Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - D. V. Petrovski
- The federal research center Institute of Cytology and Genetics Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - A. P. Sarapultsev
- Institute of Immunology and Physiology of the Ural Branch of the Russian Academy of Sciences, Ekaterinburg, Russia
- Federal State Autonomous Educational Institution of Higher Professional Education, Ural Federal University named after the first President of Russia B. N. Yeltsin, Ekaterinburg, Russia
| | - O. N. Chupakhin
- Federal State Autonomous Educational Institution of Higher Professional Education, Ural Federal University named after the first President of Russia B. N. Yeltsin, Ekaterinburg, Russia
- Institute of Organic Synthesis, Ural Division of Russian Academy of Sciences, Ekaterinburg, Russia
| | - M. P. Moshkin
- The federal research center Institute of Cytology and Genetics Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
- Tomsk State University, Department of Vertebrate Zoology, Tomsk, Russia
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14
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El Bitar N, Pollin B, Karroum E, Pincedé I, Le Bars D. Entanglement between thermoregulation and nociception in the rat: the case of morphine. J Neurophysiol 2016; 116:2473-2496. [PMID: 27605533 PMCID: PMC5133307 DOI: 10.1152/jn.00482.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 09/03/2016] [Indexed: 11/22/2022] Open
Abstract
In thermoneutral conditions, rats display cyclic variations of the vasomotion of the tail and paws, the most widely used target organs in current acute or chronic animal models of pain. Systemic morphine elicits their vasoconstriction followed by hyperthermia in a naloxone-reversible and dose-dependent fashion. The dose-response curves were steep with ED50 in the 0.5-1 mg/kg range. Given the pivotal functional role of the rostral ventromedial medulla (RVM) in nociception and the rostral medullary raphe (rMR) in thermoregulation, two largely overlapping brain regions, the RVM/rMR was blocked by muscimol: it suppressed the effects of morphine. "On-" and "off-" neurons recorded in the RVM/rMR are activated and inhibited by thermal nociceptive stimuli, respectively. They are also implicated in regulating the cyclic variations of the vasomotion of the tail and paws seen in thermoneutral conditions. Morphine elicited abrupt inhibition and activation of the firing of on- and off-cells recorded in the RVM/rMR. By using a model that takes into account the power of the radiant heat source, initial skin temperature, core body temperature, and peripheral nerve conduction distance, one can argue that the morphine-induced increase of reaction time is mainly related to the morphine-induced vasoconstriction. This statement was confirmed by analyzing in psychophysical terms the tail-flick response to random variations of noxious radiant heat. Although the increase of a reaction time to radiant heat is generally interpreted in terms of analgesia, the present data question the validity of using such an approach to build a pain index.
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Affiliation(s)
- Nabil El Bitar
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Bernard Pollin
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Elias Karroum
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Ivanne Pincedé
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Daniel Le Bars
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
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15
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Minervini V, Dahal S, France CP. Behavioral Characterization of κ Opioid Receptor Agonist Spiradoline and Cannabinoid Receptor Agonist CP55940 Mixtures in Rats. J Pharmacol Exp Ther 2016; 360:280-287. [PMID: 27903642 DOI: 10.1124/jpet.116.235630] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 11/29/2016] [Indexed: 12/22/2022] Open
Abstract
Pain is a significant clinical problem, and there is a need for more effective treatments with reduced adverse effects that currently limit the use of μ opioid receptor agonists. Synthetic κ opioid receptor agonists have no abuse liability and well-documented antinociceptive effects; however, adverse effects (diuresis, dysphoria) preclude their use in the clinic. Combining κ opioids with nonopioid drugs (cannabinoid receptor agonists) allows for smaller doses of each drug to produce antinociception. This study tested whether a potentially useful effect of the κ opioid receptor agonist 2-(3,4-dichlorophenyl)-N-methyl-N-[(5R,7S,8S)-7-pyrrolidin-1-yl-1-oxaspiro[4.5]decan-8-yl] (spiradoline; antinociception) is selectively enhanced by the cannabinoid receptor agonist 2-[(1R,2R,5R)-5-hydroxy-2-(3-hydroxypropyl) cyclohexyl]-5-(2-methyloctan-2-yl)phenol (CP55940). Cumulative dose-response functions were determined in eight male Sprague-Dawley rats for spiradoline (0.032-32.0 mg/kg, i.p.) and CP55940 (0.0032-1.0 mg/kg, i.p.) for antinociception, hypothermia, food-maintained responding, and diuresis. Alone, each drug dose dependently increased tail withdrawal latencies from 50°C water, decreased body temperature by ∼4°C, and eliminated food-maintained responding. Spiradoline, but not CP55940, significantly increased urine output at doses that eliminated responding. Smaller doses of spiradoline and CP55940 in mixtures (3:1, 1:1, and 1:3 spiradoline:CP55940) had effects comparable to those observed with larger doses of either drug administered alone: the interaction was additive for antinociception and additive or greater than additive for hypothermia and food-maintained responding. Collectively, these data fail to provide support for the use of these mixtures for treating acute pain; however, κ opioid/cannabinoid mixtures might be useful for treating pain under other conditions (e.g., chronic pain), but only if the adverse effects of both drugs are not enhanced in mixtures.
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Affiliation(s)
- Vanessa Minervini
- Departments of Pharmacology (V.M., S.D., C.P.F.) and Psychiatry (C.P.F.), University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Sujata Dahal
- Departments of Pharmacology (V.M., S.D., C.P.F.) and Psychiatry (C.P.F.), University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Charles P France
- Departments of Pharmacology (V.M., S.D., C.P.F.) and Psychiatry (C.P.F.), University of Texas Health Science Center at San Antonio, San Antonio, Texas
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16
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Wolfe AM, Kennedy LH, Na JJ, Nemzek-Hamlin JA. Efficacy of Tramadol as a Sole Analgesic for Postoperative Pain in Male and Female Mice. JOURNAL OF THE AMERICAN ASSOCIATION FOR LABORATORY ANIMAL SCIENCE : JAALAS 2015; 54:411-9. [PMID: 26224442 PMCID: PMC4521576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 10/21/2014] [Accepted: 12/05/2014] [Indexed: 03/24/2024]
Abstract
Tramadol is a centrally acting weak μ opioid agonist that has few of the adverse side effects common to other opioids. Little work has been done to establish an effective analgesic dose of tramadol specific for surgical laparotomy and visceral manipulation in mice. We used general appearance parameters to score positive indicators of pain including posture, coat condition, activity, breathing, and interactions with other mice, activity events (that is, the number of times each mouse stretched up in a 3-min period) used as an indicator of decreased pain, von Frey fibers, and plasma levels of corticosterone to determine whether tramadol at 20, 40, or 80 mg/kg prevented postoperative pain in male and female C57BL/6 mice. A ventral midline laparotomy with typhlectomy was used as a model of postoperative pain. In male mice, none of the markers differed between groups that received tramadol (regardless of dose) and the saline-treated controls. However, general appearance scores and plasma corticosterone levels were lower in female mice that received 80 mg/kg tramadol compared with saline. In summary, for severe postoperative pain after laparotomy and aseptic typhlectomy, tramadol was ineffective in male C57BL/6 mice at all doses tested. Although 80 mg/kg ameliorated postoperative pain in female C57BL/6 mice, this dose is very close to the threshold reported to cause toxic side effects, such as tremors and seizures. Therefore, we do not recommend the use of tramadol as a sole analgesic in this mouse model of postoperative pain.
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Affiliation(s)
- A Marissa Wolfe
- Unit for Laboratory Animal Medicine, University of Michigan, Ann Arbor, Michigan, USA.
| | - Lucy H Kennedy
- Animal Resource Center, Case Western Reserve University, Cleveland, Ohio, USA
| | - Jane J Na
- Unit for Laboratory Animal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Jean A Nemzek-Hamlin
- Unit for Laboratory Animal Medicine, University of Michigan, Ann Arbor, Michigan, USA
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17
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Kelechi TJ, Mueller M, King DE, Madisetti M, Prentice M. Impact of daily cooling treatment on skin inflammation in patients with chronic venous disease. J Tissue Viability 2015; 24:71-9. [PMID: 25703058 DOI: 10.1016/j.jtv.2015.01.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 01/20/2015] [Accepted: 01/29/2015] [Indexed: 10/24/2022]
Abstract
People with chronic venous disease are at high risk for developing venous leg ulcers. Inflammation is posited as a pathological factor for this chronic condition as evidenced by persistently elevated skin temperature. As part of a larger trial to test the effects of a cooling regimen on leg ulcer prevention, the objective of this preliminary study was to evaluate the first 30 days of intense daily cooling. Compared to a placebo control cuff, a gel cuff applied to the most severely affected lower leg skin for 30 min daily showed no statistically significant differences between temperatures taken in the home at baseline compared to those measured at the 1 month follow up visit. There were also no differences in temperatures noted between the two groups, although the temperatures in the treatment group were lower 30 min after treatment, an indication of adherence. There was no discernable decrease or increase in temperature at a given time point during the 30 day treatment period compared to the control group. It may be better to have patients monitor skin temperature on a daily basis and then apply the cuff as necessary, rather than requiring daily cooling based on baseline measurement. This "prn" approach may provide a sufficient cooling milieu to prevent escalation of inflammation and thwart ulcer occurrence or recurrence. Clinical trials registration #NCT01509599.
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Affiliation(s)
- Teresa J Kelechi
- Medical University of South Carolina, College of Nursing, 99 Jonathan Lucas Street MSC 160, Charleston, SC 29425, USA.
| | - Martina Mueller
- Medical University of South Carolina, College of Nursing, 99 Jonathan Lucas Street MSC 160, Charleston, SC 29425, USA
| | - Dana E King
- West Virginia University, Department of Family Medicine, Robert C. Byrd Health Sciences Center, P.O. Box 9152, Morgantown, WV 26506, USA
| | - Mohan Madisetti
- Medical University of South Carolina, College of Nursing, 99 Jonathan Lucas Street MSC 160, Charleston, SC 29425, USA
| | - Margie Prentice
- Medical University of South Carolina, College of Nursing, 99 Jonathan Lucas Street MSC 160, Charleston, SC 29425, USA
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18
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Francoeur RB. Using an innovative multiple regression procedure in a cancer population (Part II): fever, depressive affect, and mobility problems clarify an influential symptom pair (pain-fatigue/weakness) and cluster (pain-fatigue/weakness-sleep problems). Onco Targets Ther 2015; 8:57-72. [PMID: 25565866 PMCID: PMC4278791 DOI: 10.2147/ott.s68859] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Background Most patients with advanced cancer experience symptom pairs or clusters among pain, fatigue, and insomnia. However, only combinations where symptoms are mutually influential hold potential for identifying patient subgroups at greater risk, and in some contexts, interventions with “cross-over” (multisymptom) effects. Improved methods to detect and interpret interactions among symptoms, signs, or biomarkers are needed to reveal these influential pairs and clusters. I recently created sequential residual centering (SRC) to reduce multicollinearity in moderated regression, which enhances sensitivity to detect these interactions. Methods I applied SRC to moderated regressions of single-item symptoms that interact to predict outcomes from 268 palliative radiation outpatients. I investigated: 1) the hypothesis that the interaction, pain × fatigue/weakness × sleep problems, predicts depressive affect only when fever presents, and 2) an exploratory analysis, when fever is absent, that the interaction, pain × fatigue/weakness × sleep problems × depressive affect, predicts mobility problems. In the fever context, three-way interactions (and derivative terms) of the four symptoms (pain, fatigue/weakness, fever, sleep problems) are tested individually and simultaneously; in the non-fever context, a single four-way interaction (and derivative terms) is tested. Results Fever interacts separately with fatigue/weakness and sleep problems; these comoderators each magnify the pain–depressive affect relationship along the upper or full range of pain values. In non-fever contexts, fatigue/weakness, sleep problems, and depressive affect comagnify the relationship between pain and mobility problems. Conclusion Different mechanisms contribute to the pain × fatigue/weakness × sleep problems interaction, but all depend on the presence of fever, a sign/biomarker/symptom of proinflammatory sickness behavior. In non-fever contexts, depressive affect is no longer an outcome representing malaise from the physical symptoms of sickness, but becomes a fourth symptom of the interaction. In outpatient subgroups at heightened risk, single interventions could potentially relieve multiple symptoms when fever accompanies sickness malaise and in non-fever contexts with mobility problems. SRC strengthens insights into symptom pairs/clusters.
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Affiliation(s)
- Richard B Francoeur
- School of Social Work and the Center for Health Innovation, Adelphi University, Garden City, NY, USA ; Center for the Psychosocial Study of Health and Illness, Columbia University, New York, NY, USA
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19
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Sousa-Valente J, Andreou AP, Urban L, Nagy I. Transient receptor potential ion channels in primary sensory neurons as targets for novel analgesics. Br J Pharmacol 2014; 171:2508-27. [PMID: 24283624 DOI: 10.1111/bph.12532] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/11/2013] [Accepted: 11/20/2013] [Indexed: 12/12/2022] Open
Abstract
The last decade has witnessed an explosion in novel findings relating to the molecules involved in mediating the sensation of pain in humans. Transient receptor potential (TRP) ion channels emerged as the greatest group of molecules involved in the transduction of various physical stimuli into neuronal signals in primary sensory neurons, as well as, in the development of pain. Here, we review the role of TRP ion channels in primary sensory neurons in the development of pain associated with peripheral pathologies and possible strategies to translate preclinical data into the development of effective new analgesics. Based on available evidence, we argue that nociception-related TRP channels on primary sensory neurons provide highly valuable targets for the development of novel analgesics and that, in order to reduce possible undesirable side effects, novel analgesics should prevent the translocation from the cytoplasm to the cell membrane and the sensitization of the channels rather than blocking the channel pore or binding sites for exogenous or endogenous activators.
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Affiliation(s)
- J Sousa-Valente
- Anaesthetics, Pain Medicine and Intensive Care Section, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, London, UK
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20
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Novel orally available salvinorin A analog PR-38 protects against experimental colitis and reduces abdominal pain in mice by interaction with opioid and cannabinoid receptors. Biochem Pharmacol 2014; 92:618-26. [PMID: 25265540 DOI: 10.1016/j.bcp.2014.09.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 09/17/2014] [Accepted: 09/18/2014] [Indexed: 12/12/2022]
Abstract
BACKGROUND Salvinorin A (SA) is a potent anti-inflammatory diterpene isolated from the Mexican plant S. divinorum. Recently we showed that the novel SA analog, PR-38 has an inhibitory effect on mouse gastrointestinal (GI) motility mediated by opioid and cannabinoid (CB) receptors. The aim of the study was to characterize possible anti-inflammatory and antinociceptive action of PR-38 in the mouse GI tract. METHODS Macro- and microscopic colonic damage scores and myeloperoxidase activity were determined after intraperitoneal (i.p.), intracolonic (i.c.), and per os (p.o.) administration of PR-38 in the trinitrobenzene sulfonic acid (TNBS) and dextran sodium sulfate (DSS) models of colitis in mice. Additionally, MOP, KOP and CB1 protein expression was determined using Western blot analysis of mouse colon samples. The antinociceptive effect of PR-38 was examined based on the number of behavioral responses to i.c. instillation of mustard oil (MO). RESULTS The i.p. (10 mg/kg, twice daily), i.c. (10 mg/kg, twice daily) and p.o. (20 mg/kg, once daily) administration of PR-38 significantly attenuated TNBS- and DSS-induced colitis in mice. The effect of PR-38 was partially blocked by the KOP antagonist nor-binaltorphimine and CB1 antagonist AM 251. Western blot analysis showed a significant increase of MOP, KOP and CB1 receptor expression during colonic inflammation, which was reversed to the control levels by the administration of PR-38. PR-38 significantly decreased the number of pain responses after i.c. instillation of MO in the TNBS-treated mice. CONCLUSIONS Our results suggest that PR-38 has the potential to become a valuable anti-inflammatory and analgesic therapeutic for the treatment of GI inflammation.
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21
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Experimental colitis in mice is attenuated by changes in the levels of endocannabinoid metabolites induced by selective inhibition of fatty acid amide hydrolase (FAAH). J Crohns Colitis 2014; 8:998-1009. [PMID: 24530133 PMCID: PMC4136976 DOI: 10.1016/j.crohns.2014.01.025] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 01/29/2014] [Accepted: 01/29/2014] [Indexed: 02/08/2023]
Abstract
BACKGROUND AND AIMS Pharmacological treatment and/or maintenance of remission in inflammatory bowel diseases (IBD) is currently one of the biggest challenge in the field of gastroenterology. Available therapies are mostly limited to overcoming the symptoms, but not the cause of the disease. Recently, the endocannabinoid system has been proposed as a novel target in the treatment of IBD. Here we aimed to assess the anti-inflammatory action of the novel fatty acid amide hydrolase (FAAH) inhibitor PF-3845 and its effect on the endocannabinoid and related lipid metabolism during the course of experimental colitis. METHODS We used two models of experimental colitis in mice (TNBS- and DSS-induced) and additionally, we employed LC/MS/MS spectrometry to determine the changes in biolipid levels in the mouse colon during inflammation. RESULTS We showed that the FAAH inhibitor PF-3845 reduced experimental TNBS-induced colitis in mice and its anti-inflammatory action is associated with altering the levels of selected biolipids (arachidonic and oleic acid derivatives, prostaglandins and biolipids containing glycine in the mouse colon). CONCLUSIONS We show that FAAH is a promising pharmacological target and the FAAH-dependent biolipids play a major role in colitis. Our results highlight and promote therapeutic strategy based on targeting FAAH-dependent metabolic pathways in order to alleviate intestinal inflammation.
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22
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Hough LB, Nalwalk JW, Cleary RA, Phillips JG, Fang C, Yang W, Ding X. Deficits in neuronal cytochrome P450 activity attenuate opioid analgesia but not opioid side effects. Eur J Pharmacol 2014; 740:255-62. [PMID: 25062792 DOI: 10.1016/j.ejphar.2014.07.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Revised: 06/20/2014] [Accepted: 07/10/2014] [Indexed: 12/13/2022]
Abstract
Morphine-like analgesics act on µ opioid receptors in the CNS to produce highly effective pain relief, but the same class of receptors also mediates non-therapeutic side effects. The analgesic properties of morphine were recently shown to require the activity of a brain neuronal cytochrome P450 epoxygenase, but the significance of this pathway for opioid side effects is unknown. Here we show that brain P450 activity is not required for three of morphine׳s major side effects (respiratory depression, constipation, and locomotor stimulation). Following systemic or intracerebroventricular administration of morphine, transgenic mice with brain neuron - specific reductions in P450 activity showed highly attenuated analgesic responses as compared with wild-type (control) mice. However, brain P450-deficient mice showed normal morphine-induced side effects (respiratory depression, locomotor stimulation, and inhibition of intestinal motility). Pretreatment of control mice with the P450 inhibitor CC12 similarly reduced the analgesia, but not these side effects of morphine. Because activation of brain µ opioid receptors produces both opioid analgesia and opioid side effects, dissociation of the mechanisms for the therapeutic and therapy-limiting effects of opioids has important consequences for the development of analgesics with reduced side effects and/or limited addiction liability.
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Affiliation(s)
- Lindsay B Hough
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY, USA.
| | - Julia W Nalwalk
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY, USA
| | - Rachel A Cleary
- Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, NY, USA
| | | | - Cheng Fang
- Wadsworth Center, New York State Department of Health, and School of Public Health, State University of New York at Albany, Albany, NY, USA
| | - Weizhu Yang
- Wadsworth Center, New York State Department of Health, and School of Public Health, State University of New York at Albany, Albany, NY, USA
| | - Xinxin Ding
- Wadsworth Center, New York State Department of Health, and School of Public Health, State University of New York at Albany, Albany, NY, USA
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Galdino G, Romero TRL, Silva JFP, Aguiar DC, de Paula AM, Cruz JS, Parrella C, Piscitelli F, Duarte ID, Di Marzo V, Perez AC. The endocannabinoid system mediates aerobic exercise-induced antinociception in rats. Neuropharmacology 2013; 77:313-24. [PMID: 24148812 DOI: 10.1016/j.neuropharm.2013.09.022] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 09/06/2013] [Accepted: 09/20/2013] [Indexed: 10/26/2022]
Abstract
Exercise-induced antinociception is widely described in the literature, but the mechanisms involved in this phenomenon are poorly understood. Systemic (s.c.) and central (i.t., i.c.v.) pretreatment with CB₁ and CB₂ cannabinoid receptor antagonists (AM251 and AM630) blocked the antinociception induced by an aerobic exercise (AE) protocol in both mechanical and thermal nociceptive tests. Western blot analysis revealed an increase and activation of CB₁ receptors in the rat brain, and immunofluorescence analysis demonstrated an increase of activation and expression of CB₁ receptors in neurons of the periaqueductal gray matter (PAG) after exercise. Additionally, pretreatment (s.c., i.t. and i.c.v.) with endocannabinoid metabolizing enzyme inhibitors (MAFP and JZL184) and an anandamide reuptake inhibitor (VDM11) prolonged and intensified this antinociceptive effect. These results indicate that exercise could activate the endocannabinoid system, producing antinociception. Supporting this hypothesis, liquid-chromatography/mass-spectrometry measurements demonstrated that plasma levels of endocannabinoids (anandamide and 2-arachidonoylglycerol) and of anandamide-related mediators (palmitoylethanolamide and oleoylethanolamide) were increased after AE. Therefore, these results suggest that the endocannabinoid system mediates aerobic exercise-induced antinociception at peripheral and central levels.
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Affiliation(s)
- Giovane Galdino
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Ave. Antônio Carlos 6627, 31270-100 Belo Horizonte, Brazil.
| | - Thiago R L Romero
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Ave. Antônio Carlos 6627, 31270-100 Belo Horizonte, Brazil
| | - José Felipe P Silva
- Department of Physiology, Institute of Biological Sciences, Federal University of Minas Gerais, Ave. Antônio Carlos 6627, 31270-100 Belo Horizonte, Brazil
| | - Daniele C Aguiar
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Ave. Antônio Carlos 6627, 31270-100 Belo Horizonte, Brazil
| | - Ana Maria de Paula
- Biophotonics Lab, Department of Physics, Federal University of Minas Gerais, Ave. Antônio Carlos 6627, 31270-901 Belo Horizonte, Brazil
| | - Jader S Cruz
- Department of Biochemistry, Institute of Biological Sciences, Federal University of Minas Gerais, Ave. Antônio Carlos 6627, 31270-100 Belo Horizonte, Brazil
| | - Cosimo Parrella
- Endocannabinoid Research Group, Institute of Biomolecular Chemistry, National Research Council, via Campi Flegrei 34, Compresorio Olivetti, 80078 Pozzuoli, Napoli, Italy
| | - Fabiana Piscitelli
- Endocannabinoid Research Group, Institute of Biomolecular Chemistry, National Research Council, via Campi Flegrei 34, Compresorio Olivetti, 80078 Pozzuoli, Napoli, Italy
| | - Igor D Duarte
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Ave. Antônio Carlos 6627, 31270-100 Belo Horizonte, Brazil
| | - Vincenzo Di Marzo
- Endocannabinoid Research Group, Institute of Biomolecular Chemistry, National Research Council, via Campi Flegrei 34, Compresorio Olivetti, 80078 Pozzuoli, Napoli, Italy
| | - Andrea C Perez
- Department of Pharmacology, Institute of Biological Sciences, Federal University of Minas Gerais, Ave. Antônio Carlos 6627, 31270-100 Belo Horizonte, Brazil
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Opiates Modulate Thermosensation by Internalizing Cold Receptor TRPM8. Cell Rep 2013; 4:504-15. [DOI: 10.1016/j.celrep.2013.07.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 06/07/2013] [Accepted: 07/01/2013] [Indexed: 11/21/2022] Open
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Khom S, Strommer B, Schöffmann A, Hintersteiner J, Baburin I, Erker T, Schwarz T, Schwarzer C, Zaugg J, Hamburger M, Hering S. GABAA receptor modulation by piperine and a non-TRPV1 activating derivative. Biochem Pharmacol 2013; 85:1827-36. [PMID: 23623790 PMCID: PMC3776227 DOI: 10.1016/j.bcp.2013.04.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 04/15/2013] [Accepted: 04/17/2013] [Indexed: 01/11/2023]
Abstract
The action of piperine (the pungent component of pepper) and its derivative SCT-66 ((2E,4E)-5-(1,3-benzodioxol-5-yl))-N,N-diisobutyl-2,4-pentadienamide) on different gamma-aminobutyric acid (GABA) type A (GABAA) receptors, transient-receptor-potential-vanilloid-1 (TRPV1) receptors and behavioural effects were investigated. GABAA receptor subtypes and TRPV1 receptors were expressed in Xenopus laevis oocytes. Modulation of GABA-induced chloride currents (IGABA) by piperine and SCT-66 and activation of TRPV1 was studied using the two-microelectrode-voltage-clamp technique and fast perfusion. Their effects on explorative behaviour, thermoregulation and seizure threshold were analysed in mice. Piperine acted with similar potency on all GABAA receptor subtypes (EC50 range: 42.8 ± 7.6 μM (α2β2)–59.6 ± 12.3 μM (α3β2)). IGABA modulation by piperine did not require the presence of a γ2S-subunit, suggesting a binding site involving only α and β subunits. IGABA activation was slightly more efficacious on receptors formed from β2/3 subunits (maximal IGABA stimulation through α1β3 receptors: 332 ± 64% and α1β2: 271 ± 36% vs. α1β1: 171 ± 22%, p < 0.05) and α3-subunits (α3β2: 375 ± 51% vs. α5β2:136 ± 22%, p < 0.05). Replacing the piperidine ring by a N,N-diisobutyl residue (SCT-66) prevents interactions with TRPV1 and simultaneously increases the potency and efficiency of GABAA receptor modulation. SCT-66 displayed greater efficacy on GABAA receptors than piperine, with different subunit-dependence. Both compounds induced anxiolytic, anticonvulsant effects and reduced locomotor activity; however, SCT-66 induced stronger anxiolysis without decreasing body temperature and without the proconvulsive effects of TRPV1 activation and thus may serve as a scaffold for the development of novel GABAA receptor modulators.
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Affiliation(s)
- Sophia Khom
- Department of Pharmacology and Toxicology, University of Vienna, Althanstraße 14, A-1090 Wien, Austria
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A comparison of the antinociceptive and temperature responses to morphine and fentanyl derivatives in rats. Arch Pharm Res 2013; 36:501-8. [PMID: 23440583 DOI: 10.1007/s12272-013-0072-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 01/10/2013] [Indexed: 12/22/2022]
Abstract
In addition to producing antinociception, opioids exert profound effects on body temperature. This study aimed at comparing antinociceptive and hyperthermic responses between two groups of μ-opioid receptor agonists: fentanyl (4-anilinopiperidine-type) and morphine (phenanthrene-type) derivatives in rats. Analgesic activity was assessed by tail immersion test and the body temperature by insertion of a thermometer probe into the colon. Fentanyl (F), (±)-cis-3-methyl fentanyl (CM), (±)-cis-3-carbomethoxy fentanyl (C), (±)trans-3-carbomethoxy fentanyl (T) and (±)-cis-3 butyl fentanyl (B) produced dose-dependent increase in antinociception and hyperthermia. The relative order of analgesic potency was: CM(11.27)>F(1)>C(0.35)≥T(0.11)≥B(0.056). Similar to this, the relative order of hyperthermic potency was: CM(8.43)>F(1)>C(0.46)≥T(0.11)≥B(0.076). Morphine (M), oxycodone (O), thebacon (T) and 6,14-ethenomorphinan-7-methanol, 4,5-epoxy-6-fluoro-3-hydroxy-α,α,17-trimethyl-, (5α,7α) (E) also produced dose-dependent increase in antinociception and hyperthermia. Among morphine derivatives the relative order of analgesic potency was: E(56)>O(5)≥T(2.6)>M(1), and similar to this, the relative order of hyperthermic potency was: E(37)>O(3)≥T(2.3)>M(1). Morphine (phenanthrene-type) and fentanyl (4-anilinopiperidine-type) derivatives produced hyperthermia in rats at doses about 2 times lower, and 6-11 times higher, than their median antinociceptive doses, respectively. This study is first to identify difference between these two classes of opioid drugs in their potencies in producing hyperthermia. Further studies are needed to clarify the significance of these findings.
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Kaneko Y, Tajiri N, Su TP, Wang Y, Borlongan CV. Combination treatment of hypothermia and mesenchymal stromal cells amplifies neuroprotection in primary rat neurons exposed to hypoxic-ischemic-like injury in vitro: role of the opioid system. PLoS One 2012; 7:e47583. [PMID: 23077646 PMCID: PMC3471862 DOI: 10.1371/journal.pone.0047583] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Accepted: 09/17/2012] [Indexed: 11/19/2022] Open
Abstract
This study was designed to reveal the therapeutic regimen and mechanism of action underlying hypothermia treatment in combination with stem cell transplantation for ameliorating neonatal hypoxic-ischemic-like injury. Primary rat neurons were exposed to oxygen-glucose deprivation (OGD), which produced hypoxic-ischemic-like injury in vitro, then incubated at 25°C (severe hypothermia), 34°C (moderate hypothermia), and 37°C (normothermia) with or without subsequent co-culture with mesenchymal stromal cells (MSCs). Combination treatment of moderate hypothermia and MSCs significantly improved cell survival and mitochondrial activity after OGD exposure. The exposure of delta opioid human embryonic kidney cells (HEK293) to moderate hypothermia attenuated OGD-mediated cell alterations, which were much more pronounced in HEK293 cells overexpressing the delta opioid receptor. Further, the addition of delta opioid peptide to 34°C hypothermia and stem cell treatment in primary rat neurons showed synergistic neuroprotective effects against OGD which were significantly more robust than the dual combination of moderate hypothermia and MSCs, and were significantly reduced, but not completely abolished, by the opioid receptor antagonist naltrexone altogether implicating a ligand-receptor mechanism of neuroprotection. Further investigations into non-opioid therapeutic signaling pathways revealed growth factor mediation and anti-apoptotic function accompanying the observed therapeutic benefits. These results support combination therapy of hypothermia and stem cells for hypoxic-ischemic-like injury in vitro, which may have a direct impact on current clinical trials using stand-alone hypothermia or stem cells for treating neonatal encephalopathy.
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Affiliation(s)
- Yuji Kaneko
- Department of Neurosurgery and Brain Repair, University of South Florida College of Medicine, Tampa, Florida, United States of America
| | - Naoki Tajiri
- Department of Neurosurgery and Brain Repair, University of South Florida College of Medicine, Tampa, Florida, United States of America
| | - Tsung-Ping Su
- National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Yun Wang
- National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Cesar V. Borlongan
- Department of Neurosurgery and Brain Repair, University of South Florida College of Medicine, Tampa, Florida, United States of America
- * E-mail:
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The transient receptor potential channel TRPA1: from gene to pathophysiology. Pflugers Arch 2012; 464:425-58. [DOI: 10.1007/s00424-012-1158-z] [Citation(s) in RCA: 262] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 09/06/2012] [Accepted: 09/06/2012] [Indexed: 12/13/2022]
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Bhalla S, Andurkar SV, Gulati A. Involvement of α2-adrenoceptors, imidazoline, and endothelin-A receptors in the effect of agmatine on morphine and oxycodone-induced hypothermia in mice. Fundam Clin Pharmacol 2012; 27:498-509. [DOI: 10.1111/j.1472-8206.2012.01046.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 04/06/2012] [Accepted: 05/10/2012] [Indexed: 11/29/2022]
Affiliation(s)
- Shaifali Bhalla
- Department of Pharmaceutical Sciences; Chicago College of Pharmacy; Midwestern University; 555 31st Street; Downers Grove; IL; 60515; USA
| | - Shridhar V. Andurkar
- Department of Pharmaceutical Sciences; Chicago College of Pharmacy; Midwestern University; 555 31st Street; Downers Grove; IL; 60515; USA
| | - Anil Gulati
- Department of Pharmaceutical Sciences; Chicago College of Pharmacy; Midwestern University; 555 31st Street; Downers Grove; IL; 60515; USA
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New strategies to develop novel pain therapies: addressing thermoreceptors from different points of view. Pharmaceuticals (Basel) 2011; 5:16-48. [PMID: 24288041 PMCID: PMC3763626 DOI: 10.3390/ph5010016] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Revised: 12/16/2011] [Accepted: 12/21/2011] [Indexed: 01/23/2023] Open
Abstract
One approach to develop successful pain therapies is the modulation of dysfunctional ion channels that contribute to the detection of thermal, mechanical and chemical painful stimuli. These ion channels, known as thermoTRPs, promote the sensitization and activation of primary sensory neurons known as nociceptors. Pharmacological blockade and genetic deletion of thermoTRP have validated these channels as therapeutic targets for pain intervention. Several thermoTRP modulators have progressed towards clinical development, although most failed because of the appearance of unpredicted side effects. Thus, there is yet a need to develop novel channel modulators with improved therapeutic index. Here, we review the current state-of-the art and illustrate new pharmacological paradigms based on TRPV1 that include: (i) the identification of activity-dependent modulators of this thermoTRP channel; (ii) the design of allosteric modulators that interfere with protein-protein interaction involved in the functional coupling of stimulus sensing and gate opening; and (iii) the development of compounds that abrogate the inflammation-mediated increase of receptor expression in the neuronal surface. These new sites of action represent novel strategies to modulate pathologically active TRPV1, while minimizing an effect on the TRPV1 subpopulation involved in physiological and protective roles, thus increasing their potential therapeutic use.
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Kågström J, Laumola EL, Poijes N, Johansson M, Ericson AC. Assessment of the effects of changes in body temperature on cardiac electrophysiology in anaesthetised guinea pigs. J Pharmacol Toxicol Methods 2011; 65:1-7. [PMID: 22178983 DOI: 10.1016/j.vascn.2011.11.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 11/28/2011] [Accepted: 11/29/2011] [Indexed: 12/31/2022]
Abstract
INTRODUCTION Anaesthetised guinea pigs are commonly used within Safety Pharmacology to evaluate drug effects on cardiac electrophysiology. However, anesthesia compromises the ability to thermoregulate, which can be further challenged when more invasive surgery is required. As anaesthetised animals are often used when screening for cardiotoxicity, thereby influencing go/no-go decisions, we wanted to quantify the impact of small temperature changes on the recorded electrophysiological parameters. METHODS Male guinea pigs were anaesthetised by pentobarbital, placed on a pre-heated table and a rectal thermistor inserted for monitoring of body temperature. After intubation animals were vagotomised and β-blocked, and lead II ECG needle electrodes attached. Following thoracotomy an atrial pacing electrode was attached and a suction MAP electrode positioned on the ventricular epicardium. In control animals temperature was kept constant (38.1±0.1°C) over the duration of the experiment. Animals in one group were slowly warmed to 41.9°C by a heating plate and a heating lamp, and in another group slowly cooled to 34.4°C by turning off all heating equipment. MAP duration at 90% repolarisation (MAPD90), AV conduction, ECG and body temperature were recorded during cardiac pacing every 5min up to 50min. RESULTS No time-dependent changes were seen in the control group. In contrast, a linear correlation was found between changes in body temperature and MAPD90, AV conduction, QTc and QRS intervals. For each degree temperature fell below 38°C MAPD90 was prolonged by 6.1ms, and for each degree above 38°C MAPD90 was shortened by 5.3ms. Corresponding changes were seen for QTc interval and AV conduction time, while effects on the QRS interval were smaller. DISCUSSION The data highlights the importance of carefully controlling body temperature when performing electrophysiological recordings in laboratory animals. A change by a single degree can affect electrophysiological parameters by 5-10%, thus increasing the risk for a false positive or negative interpretation of cardiotoxicity.
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Affiliation(s)
- Jens Kågström
- Safety Pharmacology, Safety Assessment, AstraZeneca R&D Södertälje, S-151 85 Södertälje, Sweden.
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