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Contextual fear conditioning in virtual reality is affected by 5HTTLPR and NPSR1 polymorphisms: effects on fear-potentiated startle.

ABSTRACT: The serotonin (5-HT) and neuropeptide S (NPS) systems are discussed as important genetic modulators of fear and sustained anxiety contributing to the etiology of anxiety disorders. Sustained anxiety is a crucial characteristic of most anxiety disorders which likely develops through contextual fear conditioning. This study investigated if and how genetic alterations of the 5-HT and the NPS systems as well as their interaction modulate contextual fear conditioning; specifically, function polymorphic variants in the genes coding for the 5-HT transporter (5HTT) and the NPS receptor (NPSR1) were studied. A large group of healthy volunteers was therefore stratified for 5HTTLPR (S+ vs. LL carriers) and NPSR1 rs324981 (T+ vs. AA carriers) polymorphisms resulting in four genotype groups (S+/T+, S+/AA, LL/T+, LL/AA) of 20 participants each. All participants underwent contextual fear conditioning and extinction using a virtual reality (VR) paradigm. During acquisition, one virtual office room (anxiety context, CXT+) was paired with an unpredictable electric stimulus (unconditioned stimulus, US), whereas another virtual office room was not paired with any US (safety context, CXT-). During extinction no US was administered. Anxiety responses were quantified by fear-potentiated startle and ratings. Most importantly, we found a gene × gene interaction on fear-potentiated startle. Only carriers of both risk alleles (S+/T+) exhibited higher startle responses in CXT+ compared to CXT-. In contrast, anxiety ratings were only influenced by the NPSR1 polymorphism with AA carriers showing higher anxiety ratings in CXT+ as compared to CXT-. Our results speak in favor of a two level account of fear conditioning with diverging effects on implicit vs. explicit fear responses. Enhanced contextual fear conditioning as reflected in potentiated startle responses may be an endophenotype for anxiety disorders.

SUBMITTER: Glotzbach-Schoon E

PROVIDER: S-EPMC3632789 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Contextual fear conditioning in virtual reality is affected by 5HTTLPR and NPSR1 polymorphisms: effects on fear-potentiated startle.

Glotzbach-Schoon Evelyn E Andreatta Marta M Reif Andreas A Ewald Heike H Tröger Christian C Baumann Christian C Deckert Jürgen J Mühlberger Andreas A Pauli Paul P

Frontiers in behavioral neuroscience 20130423

The serotonin (5-HT) and neuropeptide S (NPS) systems are discussed as important genetic modulators of fear and sustained anxiety contributing to the etiology of anxiety disorders. Sustained anxiety is a crucial characteristic of most anxiety disorders which likely develops through contextual fear conditioning. This study investigated if and how genetic alterations of the 5-HT and the NPS systems as well as their interaction modulate contextual fear conditioning; specifically, function polymorph ...[more]

PMID: 23630477

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Project description:The hygiene hypothesis or "Old Friends" hypothesis proposes that inflammatory diseases are increasing in modern urban societies, due in part to reduced exposure to microorganisms that drive immunoregulatory circuits and a failure to terminate inappropriate inflammatory responses. Inappropriate inflammation is also emerging as a risk factor for anxiety disorders, affective disorders, and trauma-and stressor-related disorders, including posttraumatic stress disorder (PTSD), which is characterized as persistent re-experiencing of the trauma after a traumatic experience. Traumatic experiences can lead to long-lasting fear memories and fear potentiation of the acoustic startle reflex. The acoustic startle reflex is an ethologically relevant reflex and can be potentiated in both humans and rats through Pavlovian conditioning. Mycobacterium vaccae is a soil-derived bacterium with immunoregulatory and anti-inflammatory properties that has been demonstrated to enhance fear extinction in the fear-potentiated startle paradigm when given prior to fear conditioning. To determine if immunization with M. vaccae after fear conditioning also has protective effects, adult male Sprague Dawley rats underwent fear conditioning on days -37 and -36 followed by immunizations (3x), once per week beginning 24?h following fear conditioning, with a heat-killed preparation of M. vaccae NCTC 11659 (0.1?mg, s.c., in 100?µl borate-buffered saline) or vehicle, and, then, 3?weeks following the final immunization, were tested in the fear-potentiated startle paradigm (n?=?12 per group). Rats underwent fear extinction training on days 1 through 6 followed by spontaneous recovery 14?days later (day 20). Rats were euthanized on day 21 and brain tissue was sectioned for analysis of Tph2, Htr1a, Slc6a4, Slc22a3, and Crhr2 mRNA expression throughout the brainstem dorsal and median raphe nuclei. Immunization with M. vaccae did not affect fear expression on day 1. However, M. vaccae-immunized rats showed enhanced enhanced within-session fear extinction on day 1 and enhanced between-session fear extinction beginning on day 2, relative to vehicle-immunized controls. Immunization with M. vaccae and fear-potentiated startle had minimal effects on serotonergic gene expression when assessed 42?days after the final immunization. Together with previous studies, these data are consistent with the hypothesis that immunoregulatory strategies, such as immunization with M. vaccae, have potential for both prevention and treatment of trauma- and stressor-related psychiatric disorders.

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Contextual fear conditioning in virtual reality is affected by 5HTTLPR and NPSR1 polymorphisms: effects on fear-potentiated startle.

Publications

Contextual fear conditioning in virtual reality is affected by 5HTTLPR and NPSR1 polymorphisms: effects on fear-potentiated startle.

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