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Thorstensen JR, Taylor JL, Kavanagh JJ. Human corticospinal-motoneuronal output is reduced with 5-HT 2 receptor antagonism. J Neurophysiol 2021; 125:1279-1288. [PMID: 33596722 DOI: 10.1152/jn.00698.2020] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Animal models indicate that serotonin (5-HT) release onto motoneurons facilitates motor output, particularly during strong motor activities. However, evidence for 5-HT effects during human movement are limited. This study examined how antagonism of the 5-HT2 receptor, which is a 5-HT receptor that promotes motoneuron excitability, affects human movement. Ten healthy participants (24.2 ± 1.9 yr) ingested 8 mg of cyproheptadine (competitive 5-HT2 antagonist) in a double-blinded, placebo-controlled, repeated-measures design. Transcranial magnetic stimulation (TMS) of the motor cortex was used to elicit motor evoked potentials (MEPs) from biceps brachii. First, stimulus-response curves (90%-160% active motor threshold) were obtained during very weak elbow flexions (10% of maximal). Second, to determine if 5-HT effects are scaled to the intensity of muscle contraction, TMS at a fixed intensity was applied during elbow flexions of 20%, 40%, 60%, 80%, and 100% of maximal. Cyproheptadine reduced the size of MEPs across the stimulus-response curves (P = 0.045). Notably, MEP amplitude was 22.3% smaller for the cyproheptadine condition for the strongest TMS intensity. In addition, cyproheptadine reduced maximal torque (P = 0.045), lengthened the biceps silent period during maximal elbow flexions (P = 0.037), and reduced superimposed twitch amplitude during moderate-intensity elbow flexions (P = 0.035). This study presents novel evidence that 5-HT2 receptors influence corticospinal-motoneuronal output, which was particularly evident when a large number of descending inputs to motoneurons were active. Although it is likely that antagonism of 5-HT2 receptors reduces motoneuron gain to ionotropic inputs, supraspinal mechanisms may have also contributed to the study findings.NEW & NOTEWORTHY Voluntary contractions and responses to magnetic stimulation of the motor cortex are dependent on serotonin activity in the central nervous system. 5-HT2 antagonism decreased evoked potential size to high-intensity stimulation, and reduced torque and lengthened inhibitory silent periods during maximal contractions. We provide novel evidence that 5-HT2 receptors are involved in muscle activation, where 5-HT effects are strongest when a large number of descending inputs activate motoneurons.
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Affiliation(s)
- Jacob R Thorstensen
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
| | - Janet L Taylor
- School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia.,Neuroscience Research Australia (NeuRA), Sydney, New South Wales, Australia
| | - Justin J Kavanagh
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
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Zuniga JR, Papas AS, Daniels SE, Patrick K, Muse DD, Oreadi D, Giannakopoulos HE, Granquist EJ, Levin LM, Chou JC, Maibach H, Schachtel BP. Prevention of Opioid-Induced Nausea and Vomiting During Treatment of Moderate to Severe Acute Pain: A Randomized Placebo-Controlled Trial Comparing CL-108 (Hydrocodone 7.5 mg/Acetaminophen 325 mg/Rapid-Release, Low-Dose Promethazine 12.5 mg) with Conventional Hydrocodone 7.5 mg/Acetaminophen 325 mg. PAIN MEDICINE 2019; 20:2528-2538. [PMID: 30657996 DOI: 10.1093/pm/pny294] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVES To evaluate the prevention of opioid-induced nausea and vomiting (OINV) and the relief of moderate to severe acute pain by CL-108, a novel drug combining a low-dose antiemetic (rapid-release promethazine 12.5 mg) with hydrocodone 7.5 mg/acetaminophen 325 mg (HC/APAP) was used. METHODS This was a multicenter, randomized, double-blind, placebo- and active-controlled multidose study. After surgical extraction of two or more impacted third molar teeth (including at least one mandibular impaction), 466 patients with moderate to severe pain (measured on a categorical pain intensity scale [PI-CAT]) were randomized to CL-108, HC/APAP, or placebo. Over the next 24 hours, patients used the PI-CAT to assess pain at regular intervals whereas nausea, vomiting, and other opioid-related side effects were also assessed prospectively. Study medications were taken every four to six hours as needed; supplemental rescue analgesic and antiemetic medications were permitted. Co-primary end points were the incidence of OINV and the time-weighted sum of pain intensity differences over 24 hours (SPID24). RESULTS Relative to HC/APAP treatment alone, CL-108 treatment reduced OINV by 64% (P < 0.001). Treatment with CL-108 significantly reduced pain intensity compared with placebo (SPID24 = 16.2 vs 3.5, P < 0.001). There were no unexpected or serious adverse events. CONCLUSIONS CL-108 is a safe and effective combination analgesic/antiemetic for the prevention of OINV during treatment of moderate to severe acute pain.
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Affiliation(s)
- John R Zuniga
- Department of Surgery and Division of Oral and Maxillofacial Surgery, University of Texas Southwestern Medical Center, Dallas, Texas
| | - Athena S Papas
- Department of Diagnostic Sciences, Tufts School of Dental Medicine, Boston, Massachusetts
| | - Stephen E Daniels
- Optimal Research, LLC, Austin, Texas.,Formerly with Premier Research Group, LLC, Durham, North Carolina
| | | | | | - Daniel Oreadi
- Department of Oral and Maxillofacial Surgery, Tufts School of Dental Medicine, Boston, Massachusetts
| | - Helen E Giannakopoulos
- Department of Oral and Maxillofacial Surgery, Perelman Center for Advanced Medicine, Philadelphia, Pennsylvania
| | - Eric J Granquist
- Department of Oral and Maxillofacial Surgery, Perelman Center for Advanced Medicine, Philadelphia, Pennsylvania
| | - Lawrence M Levin
- Department of Oral and Maxillofacial Surgery, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Joli C Chou
- Department of Oral and Maxillofacial Surgery, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
| | | | - Bernard P Schachtel
- Olas Pharma, Inc. (wholly owned subsidiary of Charleston Laboratories, Inc.), Jupiter, Florida, USA
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Berman J, Brown T, Dow G, Toovey S. Tafenoquine and primaquine do not exhibit clinical neurologic signs associated with central nervous system lesions in the same manner as earlier 8-aminoquinolines. Malar J 2018; 17:407. [PMID: 30400893 PMCID: PMC6219089 DOI: 10.1186/s12936-018-2555-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 10/27/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Tafenoquine was recently approved for Plasmodium vivax radical cure (KRINTAFEL™) and malaria prevention (ARAKODA™). METHODS A review of the non-clinical and clinical literature was conducted to assess whether tafenoquine (and primaquine) exhibit the same neurologic lesions and associated clinical signs as earlier 8-aminoquinolines, as has been alleged in recent opinion pieces. RESULTS Plasmocid, pamaquine and pentaquine damage specific neuro-anatomical structures in Rhesus monkeys and humans leading to corresponding deficits in neurologic function. Neurologic therapeutic indices for these 3 drugs calculated based on monkey data were well correlated with human data. Despite 60 years of use, there is no evidence that primaquine exhibits similar neurotoxicity in humans. DISCUSSION/CONCLUSIONS Extrapolation of data from Rhesus monkeys to humans, and the available clinical data, suggest that tafenoquine also does not exhibit pamaquine, pentaquine or plasmocid-like clinical neurologic signs in humans.
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Affiliation(s)
| | - Tracey Brown
- Clinical Network Services Pty Ltd, 88/4 Jephson Road, Toowong, 4066 Queensland Australia
| | - Geoffrey Dow
- 60°Pharmaceuticals LLC, 1025 Connecticut Ave NW, Suite 1000, Washington, DC 20036 USA
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Medications influencing central cholinergic pathways affect fixation stability, saccadic response time and associated eye movement dynamics during a temporally-cued visual reaction time task. Psychopharmacology (Berl) 2017; 234:671-680. [PMID: 27988806 DOI: 10.1007/s00213-016-4507-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Accepted: 12/05/2016] [Indexed: 10/20/2022]
Abstract
RATIONALE Anticholinergic medications largely exert their effects due to actions on the muscarinic receptor, which mediates the functions of acetylcholine in the peripheral and central nervous systems. In the central nervous system, acetylcholine plays an important role in the modulation of movement. OBJECTIVE This study investigated the effects of over-the-counter medications with varying degrees of central anticholinergic properties on fixation stability, saccadic response time and the dynamics associated with this eye movement during a temporally-cued visual reaction time task, in order to establish the significance of central cholinergic pathways in influencing eye movements during reaction time tasks. METHODS Twenty-two participants were recruited into the placebo-controlled, human double-blind, four-way crossover investigation. Eye tracking technology recorded eye movements while participants reacted to visual stimuli following temporally informative and uninformative cues. The task was performed pre-ingestion as well as 0.5 and 2 h post-ingestion of promethazine hydrochloride (strong centrally acting anticholinergic), hyoscine hydrobromide (moderate centrally acting anticholinergic), hyoscine butylbromide (anticholinergic devoid of central properties) and a placebo. RESULTS Promethazine decreased fixation stability during the reaction time task. In addition, promethazine was the only drug to increase saccadic response time during temporally informative and uninformative cued trials, whereby effects on response time were more pronounced following temporally informative cues. Promethazine also decreased saccadic amplitude and increased saccadic duration during the temporally-cued reaction time task. CONCLUSION Collectively, the results of the study highlight the significant role that central cholinergic pathways play in the control of eye movements during tasks that involve stimulus identification and motor responses following temporal cues.
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Naicker P, Anoopkumar-Dukie S, Grant GD, Kavanagh JJ. Medications influencing central cholinergic neurotransmission affect saccadic and smooth pursuit eye movements in healthy young adults. Psychopharmacology (Berl) 2017; 234:63-71. [PMID: 27671681 DOI: 10.1007/s00213-016-4436-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 09/12/2016] [Indexed: 11/30/2022]
Abstract
RATIONALE Acetylcholine is an important neuromodulator in the central nervous system, where it plays a significant role in central functions such as the regulation of movement. OBJECTIVE This study investigated the pharmacological effects of over-the-counter anticholinergic medications on saccadic and smooth pursuit eye movements, in order to establish the significance of central cholinergic pathways in the control of these centrally regulated oculomotor processes. METHODS Sixteen subjects (mean age 23 ± 3 years, 9 females) performed pro-saccadic, anti-saccadic and smooth pursuit eye movement tests, while an eye tracker collected eye movement data. Oculomotor assessments were performed pre-ingestion, 0.5 and 2 h post-ingestion of drugs with varying degrees of central anticholinergic properties. The drugs tested were promethazine, hyoscine hydrobromide, hyoscine butylbromide and placebo. RESULTS The drug intervention with stronger central anticholinergic properties, promethazine, decreased amplitude and increased velocity in the pro-saccadic task and increased duration in the anti-saccadic task. Promethazine, once again, was the only drug to decrease eye velocity in the smooth pursuit test. CONCLUSION The prominent effects of the stronger central anticholinergic promethazine, on saccadic and smooth pursuit eye movements, potentially conveys the significance of central cholinergic pathways in the control of these centrally regulated oculomotor processes.
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Affiliation(s)
- Preshanta Naicker
- Menzies Health Institute, Griffith University, Gold Coast, QLD, Australia.,School of Pharmacy, Griffith University, Gold Coast, QLD, Australia
| | - Shailendra Anoopkumar-Dukie
- Menzies Health Institute, Griffith University, Gold Coast, QLD, Australia.,School of Pharmacy, Griffith University, Gold Coast, QLD, Australia
| | - Gary D Grant
- Menzies Health Institute, Griffith University, Gold Coast, QLD, Australia.,School of Pharmacy, Griffith University, Gold Coast, QLD, Australia
| | - Justin J Kavanagh
- Menzies Health Institute, Griffith University, Gold Coast, QLD, Australia. .,Centre for Musculoskeletal Research, Griffith University, Gold Coast, QLD, 4222, Australia.
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Central cholinergic pathway involvement in the regulation of pupil diameter, blink rate and cognitive function. Neuroscience 2016; 334:180-190. [DOI: 10.1016/j.neuroscience.2016.08.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 08/03/2016] [Accepted: 08/05/2016] [Indexed: 11/17/2022]
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