Event-related potentials to auditory stimuli in monozygotic twins discordant for combat: association with PTSD.

Studies have demonstrated ERP abnormalities related to concentration difficulties in post-traumatic stress disorder (PTSD). We used an identical-twin, case-control design to investigate whether these abnormalities reflect pre-trauma vulnerability or the acquired consequence of PTSD. Vietnam combat veterans and their non-combat-exposed, identical twins completed a three-tone oddball task. Veterans with PTSD had delayed target N2 latencies compared to veterans without PTSD. In a small nonmedicated, nonsmoking subsample, veterans with PTSD also had significantly diminished target P3b amplitudes. A mixed-model, random-effects analysis on the nonmedicated, nonsmoking subsample that included the combat-unexposed co-twins showed a significant Diagnosis x Combat Exposure interaction for target P3b amplitude. Results replicate increased N2 latency and diminished P3b amplitude in PTSD and suggest that diminished P3b amplitude is an acquired condition in PTSD.

Intensity dependence of auditory P2 in monozygotic twins discordant for Vietnam combat: associations with posttraumatic stress disorder.

Two studies have reported decreased intensity dependence of the P2 event-related potential (ERP) in male combat veterans with posttraumatic stress disorder (PTSD), a response pattern presumed to reflect central nervous system-induced protective inhibition and heightened central serotonergic activity. We used an identical twin, case-control design to investigate whether intensity dependence abnormalities reflect pretrauma vulnerability or are an acquired consequence of PTSD. ERPs were measured in male Vietnam combat veterans and their noncombat-exposed monozygotic twin brothers during a four-tone, stimulus-intensity modulation procedure. Contrary to previous findings in male veterans, the PTSD group had significantly steeper P2 amplitude intensity slopes, similar to those reported for female veterans and abused children with PTSD. Additionally, increased P2 amplitude intensity slope was associated with increased PTSD symptom severity, particularly the severity of reexperiencing symptoms. A mixed-model, random-effects analysis that included the combat-unexposed twins revealed a significant diagnosis by combat exposure interaction. Inspection of group means suggests that the observed increased P2 intensity dependence is a consequence of PTSD. Our findings further suggest that low serotonergic tone may emerge as one potential consequence of this disorder.

PTSD arousal and depression symptoms associated with increased right-sided parietal EEG asymmetry.

Researchers have proposed that depression and particular types of anxiety are associated with unique patterns of regional brain activation. The authors examined the relationship among posttraumatic stress disorder (PTSD), anxiety, and depressive symptoms and frontal, temporal, and parietal EEG alpha asymmetry in female Vietnam War nurse veterans. The results indicate that PTSD arousal symptoms are associated with increased right-sided parietal activation. However, the combination of arousal, depression, and their interaction explain more than twice the variance in parietal asymmetry compared with arousal alone. The results support the contention that the association between anxiety and right-sided posterior activation is specific to the anxious arousal subtype. These findings underscore the importance of isolating, both theoretically and statistically, emotional subcomponents in studies of regional brain activation.

Fluoxetine differentially suppresses sucrose solution consumption in free-fed and food-deprived rats--reversal by amantadine.

BACKGROUND: Clinical use of fluoxetine and similar medications is often associated with appetite suppression and weight loss that may warrant drug discontinuation. It is unclear, however, if fluoxetine-induced consummatory suppression may be influenced by factors such as dietary status and if appetite suppressant effects of fluoxetine may be pharmacologically attenuated. MATERIAL/METHODS: Fluoxetine (0.5-10 mg/kg, i.p.) was administered to free-fed and 24 hr food-deprived adult male rats either 30 min or 4 hr prior to presentation of a sucrose solution (10% v/v). Further, amantadine (5-10 mg/kg, i.p.) and fluoxetine (5 mg/kg) were both administered either 30 min or 4 hr prior to sucrose solution presentation and intake of the solution was assessed after 2 hours of exposure. RESULTS: Fluoxetine (2-10 mg/kg) administration significantly reduced sucrose solution intake in both free-fed and food-deprived rats. However, a brief treatment-test interval (30 min) resulted in a greater suppression of intake and food-deprived rats were more resistant to the suppressant effects of fluoxetine than were sated rats. Finally, the suppressant effect of fluoxetine were reversed by acute administration of amantadine (8 mg/kg) prior to sucrose solution presentation, a dose producing no inherent stimulation of consumption. CONCLUSIONS: Acute fluoxetine administration produces a reduction in palatable substance intake that is decreased in potency with a longer treatment-test interval, an effect likely not related to pharmacokinetic considerations. Further, fluoxetine-induced consummatory suppression is reduced by prior food-deprivation. Evidence that the dopamine agonist amantadine reversed fluoxetine-induced consummatory suppression suggests a role for dopaminergic antagonism in the appetite suppressant effects of fluoxetine.

Event-related potentials to auditory stimuli in female Vietnam nurse veterans with posttraumatic stress disorder.

Individuals with posttraumatic stress disorder (PTSD) have been found to show several event-related brain potential (ERP) abnormalities including reduced target P3b amplitude, P50 suppression, and P2 amplitude/intensity slope. Female Vietnam nurse veterans with (n = 29) and without (n = 38) current PTSD completed P50 paired-click, three-tone "oddball" and four-tone stimulus-intensity modulation procedures. Opposite to previous findings, the current PTSD group had larger target P3b amplitudes and increased P2 amplitude/intensity slopes. Reduced P50 suppression was associated with increased severity of general psychopathology, but not with PTSD diagnosis. Findings suggest that target P3b amplitude and P2 amplitude/intensity slope abnormalities reflect different pathophysiological processes. Future research is needed to determine whether the opposite ERP abnormalities observed in this PTSD sample reflect gender-, trauma-, or sample-specific findings.