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Dafny N, Elizondo GM, Perez-Vasquez C. Differential Impact of Serotonin Signaling Methylphenidate on Young versus Adult: Insights from Behavioral and Dorsal Raphe Nucleus Neuronal Recordings from Freely Behaving Rats. Int J Mol Sci 2024; 25:8082. [PMID: 39125652 PMCID: PMC11311813 DOI: 10.3390/ijms25158082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 06/21/2024] [Accepted: 07/01/2024] [Indexed: 08/12/2024] Open
Abstract
Methylphenidate (MPD) remains a cornerstone pharmacological intervention for managing ADHD, yet its increasing usage among ordinary youth and adults outside clinical contexts necessitates a thorough investigation into its developmental effects. This study seeks to simultaneously investigate the behavioral and neuronal changes within the dorsal raphe (DR) nucleus, a center of serotonergic neurons in the mammalian brain, before and after the administration of varying doses of acute and chronic MPD in freely behaving young and adult rats implanted with DR recording electrodes. Wireless neuronal and behavioral recording systems were used over 10 consecutive experimental days. Eight groups were examined: saline, 0.6, 2.5, and 10.0 mg/kg MPD for both young and adult rats. Six daily MPD injections were administered on experimental days 1 to 6, followed by a three-day washout period and MPD re-administration on experimental day 10 (ED10). The analysis of neuronal activity recorded from 504 DR neurons (DRNs) in young rats and 356 DRNs in adult rats reveals significant age-dependent differences in acute and chronic MPD responses. This study emphasizes the importance of aligning electrophysiological evaluations with behavioral outcomes following extended MPD exposure, elucidating the critical role of DRNs and serotonin signaling in modulating MPD responses and delineating age-specific variations in young versus adult rat models.
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Affiliation(s)
- Nachum Dafny
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA;
| | - Gloria M. Elizondo
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA;
| | - Cruz Perez-Vasquez
- Physiology Department Medical School, National Autonomous University of Mexico, Ciudad de México 04510, Mexico
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Verhein JR, Vyas S, Shenoy KV. Methylphenidate modulates motor cortical dynamics and behavior. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.15.562405. [PMID: 37905157 PMCID: PMC10614820 DOI: 10.1101/2023.10.15.562405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Methylphenidate (MPH, brand: Ritalin) is a common stimulant used both medically and non-medically. Though typically prescribed for its cognitive effects, MPH also affects movement. While it is known that MPH noncompetitively blocks the reuptake of catecholamines through inhibition of dopamine and norepinephrine transporters, a critical step in exploring how it affects behavior is to understand how MPH directly affects neural activity. This would establish an electrophysiological mechanism of action for MPH. Since we now have biologically-grounded network-level hypotheses regarding how populations of motor cortical neurons plan and execute movements, there is a unique opportunity to make testable predictions regarding how systemic MPH administration - a pharmacological perturbation - might affect neural activity in motor cortex. To that end, we administered clinically-relevant doses of MPH to Rhesus monkeys as they performed an instructed-delay reaching task. Concomitantly, we measured neural activity from dorsal premotor and primary motor cortex. Consistent with our predictions, we found dose-dependent and significant effects on reaction time, trial-by-trial variability, and movement speed. We confirmed our hypotheses that changes in reaction time and variability were accompanied by previously established population-level changes in motor cortical preparatory activity and the condition-independent signal that precedes movements. We expected changes in speed to be a result of changes in the amplitude of motor cortical dynamics and/or a translation of those dynamics in activity space. Instead, our data are consistent with a mechanism whereby the neuromodulatory effect of MPH is to increase the gain and/or the signal-to-noise of motor cortical dynamics during reaching. Continued work in this domain to better understand the brain-wide electrophysiological mechanism of action of MPH and other psychoactive drugs could facilitate more targeted treatments for a host of cognitive-motor disorders.
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Affiliation(s)
- Jessica R Verhein
- Medical Scientist Training Program, Stanford School of Medicine, Stanford University, Stanford, CA
- Neurosciences Graduate Program, Stanford School of Medicine, Stanford University, Stanford, CA
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA
- Current affiliations: Psychiatry Research Residency Training Program, University of California, San Francisco, San Francisco, CA
| | - Saurabh Vyas
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA
- Department of Bioengineering, Stanford University, Stanford, CA
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY
| | - Krishna V Shenoy
- Neurosciences Graduate Program, Stanford School of Medicine, Stanford University, Stanford, CA
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA
- Department of Bioengineering, Stanford University, Stanford, CA
- Department of Electrical Engineering, Stanford University, Stanford, CA
- Howard Hughes Medical Institute at Stanford University, Stanford, CA
- Department of Neurobiology, Stanford University, Stanford, CA
- Bio-X Program, Stanford University, Stanford, CA
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Cid-Jofré V, Moreno M, Sotomayor-Zárate R, Cruz G, Renard GM. Modafinil Administration to Preadolescent Rat Impairs Non-Selective Attention, Frontal Cortex D 2 Expression and Mesolimbic GABA Levels. Int J Mol Sci 2022; 23:ijms23126602. [PMID: 35743046 PMCID: PMC9223864 DOI: 10.3390/ijms23126602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/26/2022] [Accepted: 06/09/2022] [Indexed: 11/16/2022] Open
Abstract
The misuse of psychostimulants is an increasing behavior among young people, highlighting in some countries the abuse of modafinil (MOD) as a neuropotentiator. However, several clinical trials are investigating MOD as an alternative pharmacological treatment for attentional deficit and hyperactivity disorder (ADHD) in children and adolescents. On the other hand, the early use of psychostimulants and the misdiagnosis rates in ADHD make it crucial to investigate the brain effects of this type of drug in young healthy individuals. The aim of this work was to evaluate the effects of chronic MOD treatment on neurochemicals (γ-aminobutyric acid and glutamate), dopamine receptor 2 (D2) expression and behavior (non-selective attention "NSA") in the mesocorticolimbic system of young healthy Sprague-Dawley rats. Preadolescent male rats were injected with MOD (75 mg/kg, i.p.) or a vehicle for 14 days (from postnatal day 22 to 35). At postnatal day 36, we measured the GLU and GABA contents and their extracellular levels in the nucleus accumbens (NAc). In addition, the GLU and GABA contents were measured in the ventral tegmental area (VTA) and D2 protein levels in the prefrontal cortex (PFC). Chronic use of MOD during adolescence induces behavioral and neurochemical changes associated with the mesocorticolimbic system, such as a reduction in PFC D2 expression, VTA GABA levels and NSA. These results contribute to the understanding of the neurological effects of chronic MOD use on a young healthy brain.
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Affiliation(s)
- Valeska Cid-Jofré
- Centro de Investigación Biomédica y Aplicada (CIBAP), Escuela de Medicina, Facultad de Ciencias Médicas, Universidad de Santiago de Chile, Obispo Umaña 050, Estación Central, Santiago 9160019, Chile; (V.C.-J.); (M.M.)
| | - Macarena Moreno
- Centro de Investigación Biomédica y Aplicada (CIBAP), Escuela de Medicina, Facultad de Ciencias Médicas, Universidad de Santiago de Chile, Obispo Umaña 050, Estación Central, Santiago 9160019, Chile; (V.C.-J.); (M.M.)
- Escuela de Psicología, Facultad de Ciencias Sociales, Universidad Bernardo O’Higgins, Santiago 8370993, Chile
| | - Ramón Sotomayor-Zárate
- Laboratorio de Neuroquímica y Neurofarmacología, Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Valparaíso 2360102, Chile;
| | - Gonzalo Cruz
- Laboratorio de Alteraciones Reproductivas y Metabólicas, Centro de Neurobiología y Fisiopatología Integrativa (CENFI), Instituto de Fisiología, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Valparaíso 2360102, Chile;
| | - Georgina M. Renard
- Centro de Investigación Biomédica y Aplicada (CIBAP), Escuela de Medicina, Facultad de Ciencias Médicas, Universidad de Santiago de Chile, Obispo Umaña 050, Estación Central, Santiago 9160019, Chile; (V.C.-J.); (M.M.)
- Correspondence:
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Methylphenidate ameliorates the homeostatic balance between levels of kynurenines in ADHD children. Psychiatry Res 2021; 303:114060. [PMID: 34175711 DOI: 10.1016/j.psychres.2021.114060] [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: 05/10/2020] [Accepted: 06/11/2021] [Indexed: 12/25/2022]
Abstract
The kynurenine pathway of tryptophan metabolism has been involved in ADHD We quantified basal levels and daily fluctuations of tryptophan and several kynurenine metabolites, as well as their changes after treatment with methylphenidate (MPH). A total of 179 children were recruited, grouped into ADHD (n = 130) and healthy controls (CG,n = 49). Blood samples were drawn at 20:00 and 09:00 h and only in the ADHD group after 4.63±2.3 months of treatment. Nocturnal urine was collected between both draws. Factorial analysis (Stata12.0) was performed with Groups, Time, Hour of Day and Depressive Symptoms (DS) as factors. MPH significantly increased plasma Kynurenic acid (2.4 ± 1.03/2.78±1.3 ng/mL; baseline/post-treatment, morning; z = 1.96,p<0.05) and Xanthurenic acid (2.39±0.95/2.88±1.19 ng/mL; baseline/post, morning; z = 2.7,p<0.007) levels, both with higher values in the evening. In DS+ patients, MPH caused a pronounced decrease in evening Anthranilic acid [3.08±5.02/ 1.82±1.46 ng/mL, z = 2.68,p = 0.0074] until matching values to other subgroups. In urine, MPH decreased the excretion of both Nicotinamide and Quinolinic acids, but only in the DS- subgroup. The kynurenine pathway may participate in the highly clinical favorable response to MPH. The observed changes could be considered as protective (i.e. increased plasma kynurenic acid vs. decreased quinolinic acid excretion) based on the knowledge of its physiological homeostatic functions.
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