Cerebral GABA and Fear Conditioning in PTSD

NCT ID: NCT01800383

Last Updated: 2023-04-04

Basic Information

• Recruitment Status: COMPLETED
• Total Enrollment: 126 participants
• Study Classification: OBSERVATIONAL
• Study Start Date: 2013-02-28
• Study Completion Date: 2022-12-31

Brief Summary

Posttraumatic stress disorder (PTSD) is a common and debilitating neuropsychiatric disorder in which an acute fear response to a traumatic event does not abate. This failure to recover from trauma is thought to be due at least in part to a deficit in learning not to fear situations and stimuli previously associated with the trauma (i.e., specifically due to a failure of extinction recall). Pavlovian fear conditioning can be simulated and measured experimentally in humans using a 2-day fear conditioning paradigm developed by our group, wherein conditioning and extinction learning phases are conducted on Day 1, and extinction recall is tested on Day 2.

Recent functional magnetic resonance imaging (fMRI) evidence indicates that PTSD is associated with hyper-responsivity of the insular cortex and hyporesponsivity of the ventromedial prefrontal cortex (VMPFC) during exposure to fear-inducing stimuli, consistent with altered excitability of brain regions mediating fear conditioning and extinction. As the brain's principal inhibitory neurotransmitter, GABA exerts a prominent role in modulating neuronal excitability. Interestingly, there are reports that adjunctive treatment with GABA-enhancing antiepileptics is efficacious in PTSD. There is also evidence, albeit inconsistent, that lower serum GABA levels predict a more chronic course of the illness. However, it is unclear whether serum levels accurately reflect brain GABA, which may contribute to inconsistency of serum findings. Moreover, it is possible that GABA alterations may vary in their presence, nature and significance across brain regions implicated in PTSD. The proposed study will examine the relationship of PTSD symptoms and behavioral fear conditioning deficits with regional brain gamma-aminobutyric acid (GABA) using proton magnetic resonance spectroscopy (1H-MRS).

We have the following aims and hypotheses:

1. To determine whether GABA alterations are associated with the categorical diagnosis of PTSD and not merely exposure to trauma. It is hypothesized that PTSD will be associated with higher GABA in VMPFC and lower GABA in the right insula.

2. To determine whether GABA levels are significantly associated with dimensional measures of PTSD symptom severity and individual symptom dimensions. It is predicted that higher GABA in the VMPFC and lower GABA in the right anterior insula will be associated with greater total symptom severity.

3. To determine whether GABA in VMPFC and right anterior insula are significantly associated with measures of extinction recall failure and anxiety sensitivity in PTSD. It is hypothesized that VMPFC GABA will be positively correlated with skin conductance response to a conditioned stimulus that had previously been extinguished and insula GABA will be negatively correlated with anxiety sensitivity.

Conditions

Stress Disorders, Post-Traumatic

Study Design

• Observational Model Type: CASE_CONTROL
• Study Time Perspective: CROSS_SECTIONAL

Study Groups

Control

No Axis I psychiatric disorder and no trauma exposure

No interventions assigned to this group

Trauma-Exposed Normal Control

History of trauma exposure and subthreshold PTSD symptoms.

No interventions assigned to this group

PTSD

Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) diagnosis of PTSD as determined by the Structured Clinical Interview for DSM-IV-Text Revised

No interventions assigned to this group

Eligibility Criteria

Inclusion Criteria

• 20-50 years of age
• right-handed
• DSM-IV diagnosis consistent with group assignment
• groups to be matched for age, sex, education, race/ethnicity
• ability to provide written informed consent
• groups to be matched on proportion of female subjects in follicular/luteal menstrual phases.

Exclusion Criteria

• Medical condition that would confound results
• history of seizures or head trauma with loss of consciousness
• exposure to psychotropic medications within 4 weeks of study (8 weeks for fluoxetine)
• metal implants, claustrophobia or other Magnetic Resonance Imaging (MRI) exclusions
• positive urine toxicology or human chorionic gonadotropin (HCG) status on scan day
• history of psychotic disorder, bipolar disorder, eating disorder, mental retardation, or pervasive developmental disorder; history of meeting full criteria for non-PTSD anxiety disorder.
• PTSD and trauma subjects will be matched in terms of comorbid depressive disorder, not to exceed 50%. Trauma-exposed subjects will have a history of trauma exposure and will not meet criteria for PTSD. Non-traumatized healthy subjects will have no history of Axis I psychiatric disorder and no trauma exposure.

• Minimum Eligible Age: 20 Years
• Maximum Eligible Age: 50 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

Mclean Hospital

OTHER

Sponsor Role: collaborator

Isabelle Rosso

OTHER

Sponsor Role: lead

Responsible Party

Isabelle Rosso

Director, Anxiety and Traumatic Stress Disorders Laboratory

Responsibility Role: SPONSOR_INVESTIGATOR

Locations

McLean Hospital

Belmont, Massachusetts, United States

Countries

United States

Other Identifiers

MH096987-01A1

Identifier Type: -

Identifier Source: org_study_id