Association of rs7688285 allelic variation coding for GLRB with fear reactivity and exposure-based therapy in patients with panic disorder and agoraphobia.

The gene coding for glycine receptor ß subunits (GLRB) has been found to be related to panic disorder and agoraphobia (PD/AG) and to be associated with altered insular BOLD activation during fear conditioning, as an intermediate phenotype of defensive system reactivity in healthy subjects. In a multicenter clinical trial on PD/AG patients we investigated in three sub-samples whether GLRB allelic variation (A/G; A-allele identified as «risk¼) in the single nucleotide polymorphism rs7688285 was associated with autonomic (behavioral avoidance test BAT; n = 267 patients) and neural (differential fear conditioning; n = 49 patients, n = 38 controls) measures, and furthermore with responding towards exposure-based cognitive behavioral therapy (CBT, n = 184 patients). An interaction of genotype with current PD/AG diagnosis (PD/AG vs. controls; fMRI data only) and their modification after CBT was tested as well. Exploratory fMRI results prior to CBT, revealed A-allele carriers irrespective of diagnostic status to show overall higher BOLD activation in the hippocampus, motor cortex (MC) and insula. Differential activation in the MC, anterior cingulate cortex (ACC) and insula was found in the interaction genotype X diagnosis. Differential activation in ACC and hippocampus was present in differential fear learning. ACC activation was modified after treatment, while no overall rs7688285 dependent effect on clinical outcomes was found. On the behavioral level, A-allele carriers showed pronounced fear reactivity prior to CBT which partially normalized afterwards. In sum, rs7688285 variation interacts in a complex manner with PD/AG on a functional systems level and might be involved in the development of PD/AG but not in their treatment.

The impact of depressive comorbidity on neural plasticity following cognitive-behavioral therapy in panic disorder with agoraphobia.

BACKGROUND: Depressive disorders are a frequent comorbidity of panic disorder with agoraphobia (PD/AG). Cognitive-behavioral therapy (CBT) for PD/AG effectively reduces anxiety and depressive symptoms, irrespective of comorbidities. However, as depressive comorbidities can confound fear circuitry activation (i.e. amygdalae, insulae, anterior cingulate cortex) in PD/AG, we investigated whether comorbid depressive disorders alter neural plasticity following CBT. METHODS: Within a randomized, controlled clinical trial on exposure-based CBT, forty-two PD/AG patients including fifteen (35.7%) with a comorbid depressive disorder (PD/AG + DEP) participated in a longitudinal functional magnetic resonance imaging (fMRI) study. A differential fear conditioning task was used as probe of interest. A generalized psycho-physiological interaction analysis (gPPI) served to study functional connectivity patterns. RESULTS: After CBT, only PD/AG patients without comorbid depressive disorders (PD/AG-DEP) showed reduced activation in the left inferior frontal gyrus (IFG) extending to the insula. While PD/AG-DEP patients showed enhanced functional connectivity (FC) between the left IFG and subcortical structures (anterior cingulate cortex, thalamus and midbrain), PD/AG + DEP patients exhibited increased FC between the left IFG and cortical structures (prefrontal, parietal regions). In both groups, FC decreased following CBT. LIMITATIONS: Primary depressed and medicated patients were excluded. Major depression and dysthymia were collapsed. CONCLUSIONS: Reduced activation in the left IFG, as previously shown in PD/AG, appears to be a specific substrate of CBT effects in PD/AG-DEP patients only. Differential patterns of FC pertaining to fear circuitry networks in patients without depression vs. cognitive networks in patients with comorbid depression may point towards different pathways recruited by CBT as a function of comorbidity.