Impaired fear memory in a rat model of the brain-derived neurotrophic factor Val66Met polymorphism is reversed by chronic exercise

Emily J Jaehne; Emily J Antolasic; Kerstin C Creutzberg; Veronica Begni; Marco A Riva; Maarten van den Buuse

doi:10.1016/j.nlm.2023.107779

Impaired fear memory in a rat model of the brain-derived neurotrophic factor Val66Met polymorphism is reversed by chronic exercise

Neurobiol Learn Mem. 2023 Sep:203:107779. doi: 10.1016/j.nlm.2023.107779. Epub 2023 Jun 1.

Authors

Emily J Jaehne¹, Emily J Antolasic¹, Kerstin C Creutzberg², Veronica Begni², Marco A Riva³, Maarten van den Buuse⁴

Affiliations

¹ Department of Psychology, Counselling and Therapy, School of Psychology and Public Health, La Trobe University, Melbourne, Australia.
² Department of Pharmacological and Biomolecular Sciences, University of Milan, Milan, Italy.
³ Department of Pharmacological and Biomolecular Sciences, University of Milan, Milan, Italy; Biological Psychiatry Laboratory, IRCCS Istituto Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy.
⁴ Department of Psychology, Counselling and Therapy, School of Psychology and Public Health, La Trobe University, Melbourne, Australia; Department of Pharmacology, University of Melbourne, Melbourne, Australia. Electronic address: m.vandenbuuse@latrobe.edu.au.

PMID: 37269900
DOI: 10.1016/j.nlm.2023.107779

Abstract

The brain-derived neurotrophic factor (BDNF) Val66Met polymorphism is associated with reduced activity-dependent BDNF release in the brain and has been implicated in fear and anxiety disorders, including post-traumatic stress disorder. Exercise has been shown to have benefits in affective disorders but the role of BDNF Val66Met remains unclear. Male and female BDNF Val66Met rats were housed in automated running-wheel cages from weaning while controls were housed in standard cages. During adulthood, all rats underwent standard three-day fear conditioning testing, with three tone/shock pairings on day 1 (acquisition), and extinction learning and memory (40 tones/session) on day 2 and day 3. Expression of BDNF and stress-related genes were measured in the frontal cortex. Extinction testing on day 2 revealed significantly lower freezing in response to initial cue exposure in control Met/Met rats, reflecting impaired fear memory. This deficit was reversed in both male and female Met/Met rats exposed to exercise. There were no genotype effects on acquisition or extinction of fear, however chronic exercise increased freezing in all groups at every stage of testing. Exercise furthermore led to increased expression of Bdnf in the prefrontal cortex of females and its isoforms in both sexes, as well as increased expression of FK506 binding protein 51 (Fkpb5) in females and decreased expression of Serum/glucocorticoid-regulated kinase (Sgk1) in males independent of genotype. These results show that the Met/Met genotype of the Val66Met polymorphism affects fear memory, and that chronic exercise selectively reverses this genotype effect. Chronic exercise also led to an overall increase in freezing in all genotypes which may contribute to results.

Keywords: Brain-derived neurotrophic factor; Exercise; Fear conditioning; PTSD; Val66Met.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Brain / metabolism
Brain-Derived Neurotrophic Factor* / genetics
Brain-Derived Neurotrophic Factor* / metabolism
Fear / physiology
Female
Learning
Male
Memory Disorders
Polymorphism, Single Nucleotide*
Rats

Substances

Brain-Derived Neurotrophic Factor