1
|
Tripp G, Wickens J. Using rodent data to elucidate dopaminergic mechanisms of ADHD: Implications for human personality. PERSONALITY NEUROSCIENCE 2024; 7:e2. [PMID: 38384667 PMCID: PMC10877278 DOI: 10.1017/pen.2023.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 10/11/2023] [Accepted: 10/22/2023] [Indexed: 02/23/2024]
Abstract
An altered behavioral response to positive reinforcement has been proposed to be a core deficit in attention deficit hyperactivity disorder (ADHD). The spontaneously hypertensive rat (SHR), a congenic animal strain, displays a similarly altered response to reinforcement. The presence of this genetically determined phenotype in a rodent model allows experimental investigation of underlying neural mechanisms. Behaviorally, the SHR displays increased preference for immediate reinforcement, increased sensitivity to individual instances of reinforcement relative to integrated reinforcement history, and a steeper delay of reinforcement gradient compared to other rat strains. The SHR also shows less development of incentive to approach sensory stimuli, or cues, that predict reward after repeated cue-reward pairing. We consider the underlying neural mechanisms for these characteristics. It is well known that midbrain dopamine neurons are initially activated by unexpected reward and gradually transfer their responses to reward-predicting cues. This finding has inspired the dopamine transfer deficit (DTD) hypothesis, which predicts certain behavioral effects that would arise from a deficient transfer of dopamine responses from actual rewards to reward-predicting cues. We argue that the DTD predicts the altered responses to reinforcement seen in the SHR and individuals with ADHD. These altered responses to reinforcement in turn predict core symptoms of ADHD. We also suggest that variations in the degree of dopamine transfer may underlie variations in personality dimensions related to altered reinforcement sensitivity. In doing so, we highlight the value of rodent models to the study of human personality.
Collapse
Affiliation(s)
- Gail Tripp
- Human Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Jeff Wickens
- Neurobiology Research Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| |
Collapse
|
2
|
Lara MK, Chitre AS, Chen D, Johnson BB, Nguyen KM, Cohen KA, Muckadam SA, Lin B, Ziegler S, Beeson A, Sanches T, Solberg Woods LC, Polesskaya O, Palmer AA, Mitchell SH. Genome-wide association study of delay discounting in Heterogenous Stock rats. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.12.570851. [PMID: 38168347 PMCID: PMC10760013 DOI: 10.1101/2023.12.12.570851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Delay discounting refers to the behavioral tendency to devalue rewards as a function of their delay in receipt. Heightened delay discounting has been associated with substance use disorders, as well as multiple co-occurring psychopathologies. Genetic studies in humans and animal models have established that delay discounting is a heritable trait, but only a few specific genes have been associated with delay discounting. Here, we aimed to identify novel genetic loci associated with delay discounting through a genome-wide association study (GWAS) using Heterogenous Stock rats, a genetically diverse outbred population derived from eight inbred founder strains. We assessed delay discounting in 650 male and female rats using an adjusting amount procedure in which rats chose between smaller immediate sucrose rewards or a larger reward at variable delays. Preference switch points were calculated for each rat and both exponential and hyperbolic functions were fitted to these indifference points. Area under the curve (AUC) and the discounting parameter k of both functions were used as delay discounting measures. GWAS for AUC, exponential k, and indifference points for a short delay identified significant loci on chromosomes 20 and 14. The gene Slc35f1, which encodes a member of the solute carrier family of nucleoside sugar transporters, was the only gene within the chromosome 20 locus. That locus also contained an eQTL for Slc35f1, suggesting that heritable differences in the expression of that gene might be responsible for the association with behavior. The gene Adgrl3, which encodes a member of the latrophilin family of G-protein coupled receptors, was the only gene within the chromosome 14 locus. These findings implicate novel genes in delay discounting and highlight the need for further exploration.
Collapse
Affiliation(s)
- Montana Kay Lara
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Apurva S. Chitre
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Denghui Chen
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Benjamin B. Johnson
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Khai-Minh Nguyen
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Katarina A. Cohen
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Sakina A. Muckadam
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Bonnie Lin
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Shae Ziegler
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Angela Beeson
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC, 27157, USA
| | - Thiago Sanches
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Leah C. Solberg Woods
- Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC, 27157, USA
| | - Oksana Polesskaya
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
| | - Abraham A. Palmer
- Department of Psychiatry, University of California San Diego, La Jolla, CA, 92093, USA
- Institute for Genomic Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Suzanne H. Mitchell
- Departments of Behavioral Neuroscience, Psychiatry, the Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, 97239 USA
| |
Collapse
|