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Roghani M, Ghaedi G, Iranzadeh S, Golezar MH, Afshinmajd S. Efficacy and safety of venlafaxine versus nortriptyline for the preventive treatment of migraine: A double-blind randomized clinical trial. Clin Neurol Neurosurg 2024; 243:108400. [PMID: 38901375 DOI: 10.1016/j.clineuro.2024.108400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2024] [Revised: 06/13/2024] [Accepted: 06/15/2024] [Indexed: 06/22/2024]
Abstract
OBJECTIVE Migraine, as a primary headache disorder, stands as one of the primary causes of disability worldwide. Consequently, prophylactic treatments are highly recommended for individuals experiencing recurrent migraine episodes. Our study aimed to compare the efficacy and safety profiles of venlafaxine and nortriptyline in the prophylactic management of migraine. METHODS In this single-center, randomized, double-blind clinical trial, 210 migraine patients were allocated into two groups in a 1:1 ratio. One group received venlafaxine (37.5 mg, orally twice daily), while the other group administered nortriptyline (25 mg, orally once daily). A neurologist documented (1) headache intensity using the Visual Analog Scale (VAS) and 6-point Behavioral Rating Scale (BRS-6), (2) headache frequency (per month), and (3) headache duration (in hours) of participants on days 0, 45, and 90 of the intervention. RESULTS Following the 90-day intervention, a significant decrease was observed in VAS, BRS-6, frequency, and duration of headaches within both groups (all with p-values <0.001). No difference in VAS, BRS-6, or headache durations was observed between the two groups after 45 and 90 days of treatment (all p-values > 0.05). Although the headache frequency exhibited no difference between the groups after 45 days (p-value = 0.097), a significantly lower frequency in the venlafaxine group was observed at day 90 of the intervention (p-value = 0.011). The reductions in attack parameters in the 0-45- and 0-90-day intervals did not meet statistical significance between the two groups (p-values > 0.05). 77.0 % of the participants in the venlafaxine group and 79.2 % in the nortriptyline group experienced a minimum of 50 % improvement in all attack parameters. Venlafaxine demonstrated a statistically significant lower incidence of adverse reactions in comparison to nortriptyline (p-value = 0.005). A total of 33 adverse drug reactions were documented in the venlafaxine group and 53 in the nortriptyline group, with insomnia observed in the former and xerostomia in the latter as the most prevalent side effects. CONCLUSIONS Venlafaxine and nortriptyline demonstrate clinically significant and comparable therapeutic efficacy for migraine patients in reducing the intensity, frequency, and duration of headache attacks. Venlafaxine may be preferred to nortriptyline in the context of migraine preventive treatment under comparable conditions due to its lower incidence of adverse effects.
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Affiliation(s)
- Mehrdad Roghani
- Neurophysiology Research Center, Shahed University, Tehran, Iran
| | | | | | | | - Siamak Afshinmajd
- Neurophysiology Research Center, Shahed University, Tehran, Iran; Department of Neurology, Faculty of Medicine, Shahed University, Tehran, Iran.
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Hillhouse TM, Partridge KJ, Garrett PI, Honeycutt SC, Porter JH. Effects of (2R,6R)-hydroxynorketamine in assays of acute pain-stimulated and pain-depressed behaviors in mice. PLoS One 2024; 19:e0301848. [PMID: 38640139 PMCID: PMC11029659 DOI: 10.1371/journal.pone.0301848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Accepted: 03/22/2024] [Indexed: 04/21/2024] Open
Abstract
Ketamine has been shown to produce analgesia in various acute and chronic pain states; however, abuse liability concerns have limited its utility. The ketamine metabolite (2R,6R)-hydroxynorketamine (HNK) has been shown to produce antidepressant-like effects similar to ketamine without abuse liability concerns. (2R,6R)-HNK produces sustained analgesia in models of chronic pain, but has yet to be evaluated in models of acute pain. The present study evaluated the efficacy of acute (2R,6R)-HNK administration (one injection) in assays of pain-stimulated (52- and 56-degree hot plate test and acetic acid writhing) and pain-depressed behavior (locomotor activity and rearing) in male and female C57BL/6 mice. In assays of pain-stimulated behaviors, (2R,6R)-HNK (1-32 mg/kg) failed to produce antinociception in the 52- and 56-degree hot plate and acetic acid writhing assays. In assays of pain-depressed behaviors, 0.56% acetic acid produced a robust depression of locomotor activity and rearing that was not blocked by pretreatment of (2R,6R)-HNK (3.2-32 mg/kg). The positive controls morphine (hot plate test) and ketoprofen (acetic acid writhing, locomotor activity, and rearing) blocked pain-stimulated and pain-depressed behaviors. Finally, the effects of intermittent (2R,6R)-HNK administration were evaluated in 52-degree hot plate and pain-depressed locomotor activity and rearing. Intermittent administration of (2R,6R)-HNK also did not produce antinociceptive effects in the hot plate or pain-depressed locomotor activity assays. These results suggest that (2R,6R)-HNK is unlikely to have efficacy in treating acute pain; however, the efficacy of (2R,6R)-HNK in chronic pain states should continue to be evaluated.
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Affiliation(s)
- Todd M. Hillhouse
- Department of Psychology, University of Wisconsin Green Bay, Green Bay, Wisconsin, United States of America
| | - Kaitlyn J. Partridge
- Department of Psychology, University of Wisconsin Green Bay, Green Bay, Wisconsin, United States of America
- Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
| | - Patrick I. Garrett
- Department of Pharmacology and Toxicology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, United States of America
| | - Sarah C. Honeycutt
- Department of Psychology, University at Buffalo, Buffalo, New York, United States of America
| | - Joseph H. Porter
- Department of Psychology, Virginia Commonwealth University, Richmond, Virginia, United States of America
- Department of Psychological Sciences, Northern Michigan, Marquette, Michigan, United States of America
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Liu H, Wu Y, Li C, Tang Q, Zhang YW. Molecular docking and biochemical validation of (-)-syringaresinol-4-O-β-D-apiofuranosyl-(1→2)-β-D-glucopyranoside binding to an allosteric site in monoamine transporters. Front Pharmacol 2022; 13:1018473. [PMID: 36386236 PMCID: PMC9649612 DOI: 10.3389/fphar.2022.1018473] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 10/17/2022] [Indexed: 06/11/2024] Open
Abstract
Albizia julibrissin Durazz is one of the most common herbs used for depression and anxiety treatment, but its mechanism of action as an antidepressant or anxiolytic drug have not been fully understood. We previously isolated and identified one lignan glycoside compound from Albizia Julibrissin Durazz, (-)-syringaresinol-4-O-β-D-apiofuranosyl-(1→2)-β-D-glucopyranoside (SAG), that inhibited all three monoamine transporters with a mechanism of action different from that of the conventional antidepressants. In this study, we generated homology models for human dopamine transporter and human norepinephrine transporter, based on the X-ray structure of Drosophila dopamine transporter, and conducted the molecular docking of SAG to all three human monoamine transporters. Our computational results indicated that SAG binds to an allosteric site (S2) that has been demonstrated to be formed by an aromatic pocket positioned in the scaffold domain in the extracellular vestibule connected to the central site (S1) in these monoamine transporters. In addition, we demonstrated that SAG stabilizes a conformation of serotonin transporter with both the extracellular and cytoplasmic pathways closed. Furthermore, we performed mutagenesis of the residues in both the allosteric and orthosteric sites to biochemically validate SAG binding in all three monoamine transporters. Our results are consistent with the molecular docking calculation and support the association of SAG with the allosteric site. We expect that this herbal molecule could become a lead compound for the development of new therapeutic agents with a novel mechanism of action.
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Affiliation(s)
- Hanhe Liu
- School of Life Sciences, Guangzhou University, Guangzhou, China
| | - Yingyao Wu
- School of Life Sciences, Guangzhou University, Guangzhou, China
| | - Chan Li
- School of Life Sciences, Guangzhou University, Guangzhou, China
| | - Qingfa Tang
- School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, Guangzhou, China
| | - Yuan-Wei Zhang
- School of Life Sciences, Guangzhou University, Guangzhou, China
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Dong X, Huang R. Ferulic acid: An extraordinarily neuroprotective phenolic acid with anti-depressive properties. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2022; 105:154355. [PMID: 35908520 DOI: 10.1016/j.phymed.2022.154355] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 06/13/2022] [Accepted: 07/19/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND Depression, one of the most common mental illnesses and mood disorder syndromes, can seriously harm physical and mental health. As the pathophysiology of depression remains unclear, there is a need to find novel therapeutic agents. Ferulic acid (FA), a phenolic compound found in various Chinese herbal medicines, has anti-inflammatory and free radical scavenging properties as well as a wide range of therapeutic effects against depression. PURPOSE In this review, we appraised preclinical research to fully discuss the anti-depression capacity of FA and discussed FAs' holistic characteristics that can contribute to better management of depression. STUDY DESIGN We reviewed the results of in vitro and in vivo experiments using FA to treat depression and explored the possible antidepressant pharmacological mechanisms of FA for the clinical treatment of depression. METHODS Electronic databases, including PubMed, Google Scholar, and China National Knowledge Infrastructure, were searched from the beginning of the database creation to December 2021. RESULTS Studies on the antidepressant effects of FA show that it may exert such effects through various mechanisms. These include the following: the regulation of monoamine and non-monoamine neurotransmitter levels, inhibition of hypothalamic-pituitary-adrenal axis hyperfunction and neuroinflammation, promotion of hippocampal neurogenesis and upregulation brain-derived neurotrophic factor level, neuroprotection (inhibition of neuroinflammation, oxidative stress, mitochondrial dysfunction, and apoptosis), and downregulation of oxidative stress. CONCLUSION Preclinical studies on the antidepressant effects of FA were reviewed in this study, and research on the antidepressant mechanisms of FA was summarized, confirming that FA can exert antidepressant effects through various pharmacological mechanisms. However, more multicenter clinical case-control studies are needed to confirm the clinical efficacy of FA.
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Affiliation(s)
- Xiaoyu Dong
- Department of Neurology, Shengjing Hospital of China Medical University, Shenyang, Liaoning PR China
| | - Rui Huang
- Department of Neurology, Shengjing Hospital of China Medical University, Shenyang, Liaoning PR China.
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Baldwin AN, Banks ML, Marsh SA, Townsend EA, Venniro M, Shaham Y, Negus SS. Acute pain-related depression of operant responding maintained by social interaction or food in male and female rats. Psychopharmacology (Berl) 2022; 239:561-572. [PMID: 35043215 PMCID: PMC10053137 DOI: 10.1007/s00213-021-06048-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 12/19/2021] [Indexed: 01/26/2023]
Abstract
RATIONALE Clinically relevant pain is often associated with functional impairment and behavioral depression, including depression of social behavior. Moreover, recovery of function is a major goal in pain treatment. We used a recently developed model of operant responding for social interaction in rats to evaluate the vulnerability of social behavior to an experimental pain manipulation and the sensitivity of pain-depressed social behavior to treatment with clinically effective analgesics. METHODS Sprague-Dawley male and female rats were trained to lever press for social access to another rat, and responding was evaluated after treatment with (a) intraperitoneal injection of dilute lactic acid (IP acid; 0.18-5.6%) administered alone as a visceral noxious stimulus, (b) the mu-opioid receptor (MOR) agonist morphine (0.32-10 mg/kg) or nonsteroidal anti-inflammatory drug (NSAID) ketoprofen (10 mg/kg) administered alone, or (c) morphine or ketoprofen administered before IP acid. For comparison, the same treatments were evaluated in separate rats trained to lever press for food delivery. RESULTS Both IP acid alone and morphine alone more potently decreased responding maintained by social interaction than by food, whereas ketoprofen did not affect responding for either reinforcer. In general, analgesics were most effective to rescue operant responding when relatively low IP acid concentrations produced significant but submaximal behavioral depression; however, morphine was not effective to rescue responding for social interaction. CONCLUSIONS Operant responding maintained by social interaction was more sensitive to pain-related disruption and less responsive to opioid analgesic rescue than food-maintained operant responding. Social behavior may be especially vulnerable to depression by pain states.
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Affiliation(s)
- A N Baldwin
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - M L Banks
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - S A Marsh
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - E A Townsend
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA
| | - M Venniro
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Y Shaham
- Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute On Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - S Stevens Negus
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA.
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Cai W, Wang XF, Wei XF, Zhang JR, Hu C, Ma W, Shen WD. Does urinary metabolite signature act as a biomarker of post-stroke depression? Front Psychiatry 2022; 13:928076. [PMID: 36090365 PMCID: PMC9448878 DOI: 10.3389/fpsyt.2022.928076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 07/14/2022] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND It is difficult to conduct the precise diagnosis of post-stroke depression (PSD) in clinical practice due to the complex psychopathology of depressive disorder. Several studies showed that gas chromatography-mass spectrometry (GC-MS)-identified urinary metabolite biomarkers could significantly discriminate PSD from stroke survivors. METHODS A systematic review was performed for the keywords of "urinary metabolite" and "PSD" using Medline, Cochrane Library, Embase, Web of Science, PsycINFO, Wanfang, CNKI, CBM, and VIP database from inception to 31 March 2022. RESULTS Four related studies were included in the review. Differential urinary metabolites including lactic acid, palmitic acid, azelaic acid, and tyrosine were identified in all the included studies. As a significant deviation in the metabolite biomarker panel, glyceric acid, azelaic acid, phenylalanine, palmitic acid, pseudouridine, and tyrosine were found in at least 2 included studies, which indicated good potential for the differentiation of PSD. CONCLUSION The systematic review provided evidence that differential urinary metabolites analyzed by the GC-MS-based approach might be used as a biomarker for the diagnosis and prognosis of PSD.
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Affiliation(s)
- Wa Cai
- Department of Acupuncture, Shanghai Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Xia-Fei Wang
- Department of Neurology, Seventh People's Hospital of Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Xi-Fang Wei
- Department of Acupuncture, Shanghai Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Jing-Ruo Zhang
- Department of Acupuncture, Shanghai Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Chen Hu
- Department of Acupuncture, Shanghai Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Wen Ma
- Department of Acupuncture, Shanghai Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Wei-Dong Shen
- Department of Acupuncture, Shanghai Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, Shanghai, China
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Zamarripa CA, Pareek T, Schrock HM, Prisinzano TE, Blough BE, Sufka KJ, Freeman KB. The kappa-opioid receptor agonist, triazole 1.1, reduces oxycodone self-administration and enhances oxycodone-induced thermal antinociception in male rats. Psychopharmacology (Berl) 2021; 238:3463-3476. [PMID: 34430992 PMCID: PMC8629928 DOI: 10.1007/s00213-021-05965-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 08/10/2021] [Indexed: 12/29/2022]
Abstract
RATIONALE Triazole 1.1 is a novel kappa-opioid receptor (KOR) agonist reported to produce antinociception without KOR-typical adverse effects. When combined with the mu-opioid receptor (MOR) agonist, oxycodone, triazole 1.1 blocks oxycodone-induced pruritis without producing sedation-like effects in nonhuman primates. However, it is unknown if triazole 1.1 can reduce the abuse-related effects or enhance the antinociceptive effects of oxycodone similarly to other KOR agonists. OBJECTIVES The aim of the present study was to quantitatively compare the behavioral effects of triazole 1.1 to the KOR agonists, U50,488h and nalfurafine, on oxycodone self-administration and oxycodone-induced thermal antinociception when administered as mixtures with oxycodone. METHODS In the self-administration study, male Sprague-Dawley (SD) rats (n = 6) self-administered intravenous (i.v.) oxycodone alone (0.056 mg/kg/inj) or combined with U50,488 h (0.032-0.32 mg/kg/inj), nalfurafine (0.00032-0.0032 mg/kg/inj), or triazole 1.1 (0.32-1.8 mg/kg/inj) under a progressive-ratio schedule of reinforcement. In a hot plate assay, male SD rats (n = 6) received i.v. injections of oxycodone (1.0-5.6 mg/kg), U50,488h (1.0-18.0 mg/kg), nalfurafine (0.01-1.0 mg/kg), or triazole 1.1 (3.2-32.0 mg/kg) alone or in combinations of fixed proportion with oxycodone based on the relative potencies of the single drugs. Each study concluded with administration of the KOR antagonist nor-BNI and some degree of retesting of the previous conditions to verify that the behavioral effects were mediated by KOR activation. RESULTS All KOR agonists reduced oxycodone self-administration in a dose-dependent manner. Moreover, all single drugs and drug combinations produced dose-dependent, fully efficacious thermal antinociception. All KOR agonist:oxycodone combinations produced either additive or super-additive thermal antinociception. Finally, each KOR agonist was blocked in effect by nor-BNI in both behavioral measures. CONCLUSION This study demonstrates that triazole 1.1 reduces oxycodone's reinforcing effects and enhances oxycodone-induced antinociception to degrees that are comparable to typical KOR agonists. Given triazole 1.1's mild adverse-effect profile, developing MOR-KOR agonist combinations from the triazole 1.1 series may render new pain therapeutics with reduced abuse liability.
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Affiliation(s)
- C Austin Zamarripa
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, MS, 39216, USA
| | - Tanya Pareek
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, MS, 39216, USA
| | - Hayley M Schrock
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, MS, 39216, USA
| | | | | | - Kenneth J Sufka
- Department of Psychology, University of Mississippi, Oxford, MS, USA
| | - Kevin B Freeman
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, MS, 39216, USA.
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Lack of effect of different pain-related manipulations on opioid self-administration, reinstatement of opioid seeking, and opioid choice in rats. Psychopharmacology (Berl) 2021; 238:1885-1897. [PMID: 33765177 PMCID: PMC10041878 DOI: 10.1007/s00213-021-05816-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 03/01/2021] [Indexed: 01/26/2023]
Abstract
RATIONALE AND OBJECTIVE Pain-related factors increase the risk for opioid addiction, and pain may function as a negative reinforcer to increase opioid taking and seeking. However, experimental pain-related manipulations generally do not increase opioid self-administration in rodents. This discrepancy may reflect insufficient learning of pain-relief contingencies or confounding effects of pain-related behavioral impairments. Here, we determined if pairing noxious stimuli with opioid self-administration would promote pain-related reinstatement of opioid seeking or increase opioid choice over food. METHODS In Experiment 1, rats self-administered fentanyl in the presence or absence of repeated intraplantar capsaicin injections in distinct contexts to model context-specific exposure to cutaneous nociception. After capsaicin-free extinction in both contexts, we tested if capsaicin would reinstate fentanyl seeking. In Experiment 2, rats self-administered heroin after intraperitoneal (i.p.) lactic acid injections to model acute visceral inflammatory pain. After lactic acid-free extinction, we tested if lactic acid would reinstate heroin seeking. In Experiment 3, we tested if repeated i.p. lactic acid or intraplantar Complete Freund's Adjuvant (CFA; to model sustained inflammatory pain) would increase fentanyl choice over food. RESULTS In Experiments 1-2, neither capsaicin nor lactic acid reinstated opioid seeking after extinction, and lactic acid did not increase heroin-induced reinstatement. In Experiment 3, lactic acid and CFA decreased reinforcement rate without affecting fentanyl choice. CONCLUSIONS Results extend the range of conditions across which pain-related manipulations fail to increase opioid seeking in rats and suggest that enhanced opioid-addiction risk in humans with chronic pain involves factors other than enhanced opioid reinforcement and relapse.
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Negus SS, Marsh SA, Townsend EA. Resistance of Food-Maintained Operant Responding to Mechanical Punishment in Rats: Further Evidence for Weak "Affective/Motivational Pain" in Rat Models of Inflammatory and Neuropathic Pain. Front Pharmacol 2021; 11:615782. [PMID: 33584295 PMCID: PMC7878562 DOI: 10.3389/fphar.2020.615782] [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] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 12/29/2020] [Indexed: 01/25/2023] Open
Abstract
Clinically relevant chronic pain is often associated with functional impairment and behavioral depression as an “affective/motivational” sign of pain; however preclinical animal models of inflammatory and neuropathic pain often produce weak evidence of impaired function. We hypothesized that hindpaw mechanical stimulation produced by a requirement to rear on a textured “NOX” plate would punish operant responding in rats treated with intraplantar complete Freund’s adjuvant (CFA, a model of inflammatory pain) or the chemotherapeutic paclitaxel (PTX, a model of neuropathic pain) and produce sustained pain-related depression of operant behavior. Male Sprague–Dawley rats were trained under a progressive-ratio (PR) schedule of food-maintained operant responding, then treated with CFA (100 µL in left hindpaw), PTX (2.0 mg/kg IP on alternate days for four total injections; 6.6 mg/kg IV on alternate days for three total injections), or saline vehicle. PR break points and mechanical thresholds for paw withdrawal from von Frey filaments were then tracked for 28 days. Subsequently, rats were tested with the opioid receptor antagonist naltrexone to assess latent sensitization and with the kappa opioid receptor (KOR) agonist U69593 to assess KOR function. CFA produced significant mechanical hypersensitivity for 3 weeks but decreased PR breakpoints for only 1 day. Both IP and IV PTX produced mechanical hypersensitivity for at least three weeks; however, only IV PTX decreased PR breakpoints, and this decrease was not alleviated by morphine. After recovery, naltrexone reinstated mechanical hypersensitivity in CFA- but not PTX-treated rats, and it did not reinstate depression of breakpoints in any group. U69593 dose-dependently decreased PR breakpoints in all groups with no difference between control vs. CFA/PTX groups. These results suggest that rearing on a textured NOX plate was not sufficient to punish operant responding in CFA- and PTX-treated rats despite the presence of sustained mechanical hypersensitivity. The rapid recovery of operant responding could not be attributed to latent sensitization, KOR downregulation, or behavioral tolerance. These results extend the range of conditions under which putative chronic pain manipulations produce weak evidence for depression of operant responding as a sign of the “affective/motivational” component of pain in rats.
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Affiliation(s)
- S Stevens Negus
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States
| | - S A Marsh
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States
| | - E A Townsend
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, United States
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Attenuated dopamine receptor signaling in nucleus accumbens core in a rat model of chemically-induced neuropathy. Neuropharmacology 2020; 166:107935. [PMID: 31917153 DOI: 10.1016/j.neuropharm.2020.107935] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 12/10/2019] [Accepted: 01/02/2020] [Indexed: 02/06/2023]
Abstract
Neuropathy is major source of chronic pain that can be caused by mechanically or chemically induced nerve injury. Intraplantar formalin injection produces local necrosis over a two-week period and has been used to model neuropathy in rats. To determine whether neuropathy alters dopamine (DA) receptor responsiveness in mesolimbic brain regions, we examined dopamine D1-like and D2-like receptor (D1/2R) signaling and expression in male rats 14 days after bilateral intraplantar formalin injections into both rear paws. D2R-mediated G-protein activation and expression of the D2R long, but not short, isoform were reduced in nucleus accumbens (NAc) core, but not in NAc shell, caudate-putamen or ventral tegmental area of formalin- compared to saline-treated rats. In addition, D1R-stimulated adenylyl cyclase activity was also reduced in NAc core, but not in NAc shell or prefrontal cortex, of formalin-treated rats, whereas D1R expression was unaffected. Other proteins involved in dopamine neurotransmission, including dopamine uptake transporter and tyrosine hydroxylase, were unaffected by formalin treatment. In behavioral tests, the potency of a D2R agonist to suppress intracranial self-stimulation (ICSS) was decreased in formalin-treated rats, whereas D1R agonist effects were not altered. The combination of reduced D2R expression and signaling in NAc core with reduced suppression of ICSS responding by a D2R agonist suggest a reduction in D2 autoreceptor function. Altogether, these results indicate that intraplantar formalin produces attenuation of highly specific DA receptor signaling processes in NAc core of male rats and suggest the development of a neuropathy-induced allostatic state in both pre- and post-synaptic DA receptor function.
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