Methadone patients exhibit increased startle and cortisol response after intravenous yohimbine

Brain noradrenergic systems have been shown to be altered in opioid dependence and to mediate aspects of opioid withdrawal. Pre-clinical and clinical studies by others have shown that yohimbine, which increases noradrenergic activity, also increases both baseline and fear enhancement of the magnitude of the acoustic startle response (ASR). In a separate report from this experiment, it was shown that yohimbine produced opioid withdrawal-like symptoms, including anxiety, in clinically stable methadone-maintained patients and also produced elevations in the norepinepherine (NE) metabolite, 3-methoxy-4 hydroxyphenethyleneglycol (MHPG), and cortisol serum levels. The current study reports the effects of intravenous yohimbine hydrochloride, 0.4 mg/kg versus saline (double-blind), on ASR magnitude, plasma MHPG, and cortisol levels in eight methadone-maintained patients and 13 healthy subjects in a double-blind fashion. Yohimbine increased startle magnitude in both groups. There was no basal (placebo day) difference between the startle response of the two groups, but methadone patients had a larger startle magnitude increase in response to yohimbine than healthy controls. Methadone-maintained patients had lower baseline plasma levels of MHPG and similar baseline plasma cortisol levels compared with normal subjects. Yohimbine caused significant elevation in cortisol and MHPG in both groups. Methadone-maintained subjects had higher elevations in cortisol levels and MHPG (methadone main effect) levels in response to yohimbine. However, when MHPG levels were corrected for baseline differences by analysis of covariance (ANCOVA), the yohimbine effect, but not the methadone effect remained statistically significant. These results are consistent with the previous report and support the hypothesis that abnormalities of the hypothalamic-pituitary-adrenal (HPA) axis and of noradrenergic mechanisms of stress response persist in opioid-agonist maintenance. The ASR effect extends the previous report and provides an additional objective measure for perturbation of noradrenergic and stress responses in these patients.

Social sharing of Gulf War experiences: association with trauma-related psychological symptoms

It commonly is believed that talking with family and friends (social sharing) about stressful or traumatic experiences can be therapeutic with regard to stress-related psychological symptoms. Two years after serving in the Gulf War, 58 National Guard Reservists completed the Mississippi Posttraumatic Stress Disorder Scale (PTSD), the Brief Symptom Inventory, and a measure of social sharing that asked how much they had talked to family and friends about their experiences in the Gulf during the 2-year period since returning from the war. Subjects had a broad range of Mississippi PTSD scores. Six subjects met Mississippi criteria for PTSD. Degree of talking to family and friends about Gulf War experiences did not account for a significant portion of the variance in the prediction of PTSD symptoms but did significantly contribute to prediction of scores for interpersonal sensitivity, depression, and psychoticism. Thus, degree of talking with family and friends was not found to be related to PTSD symptoms, although it may have influenced some symptoms of general psychopathology, such as depression, that are not specific to PTSD.

The way in which the data are combined affects the interpretation of short-term feeding behavior

Short-term feeding behavior of pigs has been analyzed using random process models and log-normal models. Both were successful despite very different underlying assumptions relating to the theory of control. Feeder visits of growing pigs, housed individually from 17 to 52 kg live weight, were recorded electronically over a continuous period of 35 days. For the combined data, intervals between visits to the feeder greater than 30 min could be described well by the negative exponential model. The starting probability of a visit was constant at around 0.3, suggesting randomness. Disaggregating the data for individual pigs or for individual weeks did not change this conclusion. Intervals in the day were of a different nature to those at night, and disaggregation of the data into these two periods revealed that the negative exponential model was not satisfactory for either period. The starting probability for both periods increased with time since the last visit. This is consistent with the idea of satiety. Therefore, the apparent randomness in the data pooled across the day and night is an artefact caused by pooling itself, and is not in conflict with the satiety concept. The implications of data handling are discussed with reference to studies of the physiological control of food intake.

Hormone profiles in humans experiencing military survival training

BACKGROUND

Clinical models of the human response to intense, acute stress have been limited to laboratory settings or cross sectional characterizations. As a result, data about the sensitivity of the human neuroendocrine activation to realistic stressors of varying magnitudes are limited. The U.S. Army survival course offers a unique opportunity to examine, in a controlled manner, the human response to acute, realistic, military stress.

METHODS

Salivary data were collected in 109 subjects at baseline during four stress exposure time points and at recovery. Serum data was collected at baseline and recovery in 72 subjects and at baseline and during stress exposure in a subgroup of subjects (n = 21).

RESULTS

Cortisol significantly increased during the captivity experience and was greatest after subjects' exposure to interrogations. Cortisol remained significantly elevated at recovery. Testosterone was significantly reduced within 12 hours of captivity. Reductions of both total and free T4 and of total and free T3 were observed, as were increases in thyrotropin.

CONCLUSIONS

The stress of military survival training produced dramatic alterations in cortisol, percent free cortisol, testosterone, and thyroid indices. Different types of stressors had varying effects on the neuroendocrine indices. The degree of neuroendocrine changes observed may have significant implications for subsequent responses to stress.

Plasma neuropeptide-Y concentrations in humans exposed to military survival training

BACKGROUND

Neuropeptide-Y (NPY) is present in extensive neuronal systems of the brain and is present in high concentrations in cell bodies and terminals in the amygdala. Preclinical studies have shown that injections of NPY into the central nucleus of the amygdala function as a central anxiolytic and buffer against the effects of stress. The objective of this study was to assess plasma NPY immunoreactivity in healthy soldiers participating in high intensity military training at the U.S. Army survival school. The Army survival school provides a means of observing individuals under high levels of physical, environmental, and psychological stress, and consequently is considered a reasonable analogue to stress incurred as a result of war or other catastrophic experiences.

METHODS

Plasma levels of NPY were assessed at baseline (prior to initiation of training), and 24 hours after the conclusion of survival training in 49 subjects, and at baseline and during the Prisoner of War (P.O.W.) experience (immediately after exposure to a military interrogation) in 21 additional subjects.

RESULTS

Plasma NPY levels were significantly increased compared to baseline following interrogations and were significantly higher in Special Forces soldiers, compared to non-Special Forces soldiers. NPY elicited by interrogation stress was significantly correlated to the subjects' behavior during interrogations and tended to be negatively correlated to symptoms of reported dissociation. Twenty-four hours after the conclusion of survival training, NPY had returned to baseline in Special Forces soldiers, but remained significantly lower than baseline values in non-Special Forces soldiers. NPY was positively correlated with both cortisol and behavioral performance under stress. NPY was negatively related to psychological symptoms of dissociation.

CONCLUSIONS

These results provide evidence that uncontrollable stress significantly increases plasma NPY in humans, and when extended, produces a significant depletion of plasma NPY. Stress-induced alterations of plasma NPY were significantly different in Special Forces soldiers compared to non-Special Forces soldiers. These data support the idea that NPY may be involved in the enhanced stress resilience seen in humans.

Low baseline and yohimbine-stimulated plasma neuropeptide Y (NPY) levels in combat-related PTSD

BACKGROUND

Consistent with many studies demonstrating enhanced reactivity of the sympathetic nervous system in posttraumatic stress disorder (PTSD), the administration of yohimbine, a noradrenergic alpha(2)-antagonist, has been shown to increase core symptoms of PTSD and to induce greater increases in plasma 3-methyl-4-hydroxy-phenyl-glycol (MHPG) in subjects with PTSD compared with healthy control subjects. In turn, neuropeptide Y (NPY) has been shown to inhibit the release of norepinephrine from sympathetic noradrenergic neurons.

METHODS

In the following study, plasma NPY responses to yohimbine and placebo were measured in a subgroup of 18 subjects with PTSD and 8 healthy control subjects who participated in the previous study of the effect of yohimbine on plasma MHPG.

RESULTS

The PTSD subjects had lower baseline plasma NPY and blunted yohimbine-stimulated increases in plasma NPY compared with the healthy control subjects. Within the PTSD group, baseline plasma NPY levels correlated negatively with combat exposure scale scores, baseline PTSD and panic symptoms, and yohimbine-stimulated increases in MHPG and systolic blood pressure.

CONCLUSIONS

This study suggests that combat stress-induced decreases in plasma NPY may mediate, in part, the noradrenergic system hyperreactivity observed in combat-related PTSD. The persistence of this decrease in plasma NPY may contribute to symptoms of hyperarousal and the expression of exaggerated alarm reactions, anxiety reactions, or both in combat veterans with PTSD long after war.

Analysis of the feeding behavior of pigs using different models

Short-term feeding behavior is conventionally analysed using random process models. The assumption underlying these models have recently been questioned and this article describes the application of both random, and more biologically based, models to the feeding behavior of pigs. Feeder visits of 16 growing pigs, housed individually from 17 to 52 kg live weight, were recorded electronically over a continuous period of 35 days. Daily food intake increased linearly with time, but there was considerable individuality in the degree of order. Pigs made between 18.8 and 80.3 (mean 47.9) daily visits to the feeder. Intervals between visits could be described by two log-normal distributions. Two Gaussian density functions were fitted to the distribution of the log-transformed intervals. For the combined data from all animals the within- and between-meal intervals were 11.2 s and 100.1 min, respectively. A model with three Gaussian functions gave an improved fit to the interval distribution. The within and between meal intervals were then estimated to be 4.2 s and 93.9 min, respectively. The middle distribution of intervals ranged from 0.5 to 38.1 min. The intervals were also described by random process models; again, a three-process model gave an improved fit compared to a two-process model. The mean estimated number of meals per day from the three Gaussian model was 14.3, and from the three process random model, 16.3. A biological interpretation of the three types of interval suggests that: (1) pigs eat in meals separated by long intervals; (2) meals consist of clusters of eating bouts separated by shorter intervals, sometimes associated with drinking; (3) within each eating bout short intervals occur as pigs constantly move in and out of the feeder. It remains unclear what underlies the observed patterns of eating.

Role of norepinephrine in the pathophysiology and treatment of posttraumatic stress disorder

This review focuses on the role of norepinephrine (NE) in traumatic stress. The review is divided into three sections. The first section, "Norepinephrine and Arousal," describes preclinical studies related to norepinephrine's role in arousal, orienting to novel stimuli, selective attention and vigilance. It also contains a brief discussion of NE and its relationship to fear-provoking stimuli followed by preclinical and clinical studies that demonstrate heightened noradrenergic neuronal reactivity, increased alpha 2 receptor sensitivity and exaggerated arousal in organisms that have been exposed to chronic uncontrollable stress. The second section, "Norepinephrine and Memory," describes preclinical and clinical studies related to norepinephrine's role in enhanced encoding of memory for arousing and aversive events and in subsequent re-experiencing symptoms such as, intrusive memories and nightmares. The third section, "Norepinephrine and Pharmacologic Treatment," briefly discusses the use of adrenergic blockers, clonidine and propranol, as well as tricyclic and MAO inhibitors, for the treatment of PTSD. Finally, we attempt to synthesize trauma-related preclinical and clinical studies of norepinephrine. We do this, in part, by focusing on a series of yohimbine studies in subjects with PTSD because data from these studies allow for a discussion that brings together preclinical and clinical findings relevant to trauma-related alterations in arousal and memory.

Neurotransmitter alterations in PTSD: catecholamines and serotonin

In this chapter we review trauma-related studies involving epinephrine (E), norepinephrine (NE), and serotonin (5-HT). Central catecholamine neurons seem to play a critical role in level of alertness, vigilance, orienting, selective attention, memory, fear conditioning, and cardiovascular responses to life-threatening stimuli. Evidence of catecholamine dysregulation in post-traumatic stress disorder (PTSD) includes exaggerated increases in heart rate and blood pressure when exposed to visual and auditory reminders of trauma, elevated 24-hour urine catecholamine excretion, decreased platelet alpha-2 adrenergic receptor number, exaggerated behavioral, cardiovascular, and biochemical responses to IY yohimbine, decreased cortical brain metabolism secondary to IV yohimbine, and clinical efficacy of adrenergic blocking agents. Serotonin seems to play numerous roles in the central nervous system, including regulation of sleep, aggression, appetite, cardiovascular and respiratory activity, motor output, anxiety, mood, neuroendocrine secretion, and analgesia. Evidence of serotonergic dysregulation in PTSD includes frequent symptoms of aggression, impulsivity, depression and suicidality, decreased platelet paroxetine binding, blunted prolactin response to fenfluramine, exaggerated reactivity to m-chloro-phenyl-piperazine, and clinical efficacy of serotonin reuptake inhibitors. It has been suggested that alterations in NE, E, and 5-HT may have relevance for symptoms commonly seen in survivors with PTSD, including hypervigilance, exaggerated startle, irritability, impulsivity, aggression, intrusive memories, depressed mood, and suicidality.

Yohimbine use in a natural setting: effects on posttraumatic stress disorder

BACKGROUND

Numerous laboratory-based studies have shown that chronic posttraumatic stress disorder (PTSD) is associated with alterations in catecholamines. In a recent neuroendocrine challenge study, IV yohimbine caused exaggerated subjective, behavioral, cardiovascular and catecholamine responses among combat veterans with PTSD compared to healthy controls. Yohimbine is an alpha-2-adrenergic receptor antagonist that activates noradrenergic neurons.

METHODS

This report describes the experience of 4 individuals with PTSD who took over-the-counter oral yohimbine that they had purchased from a health food store or pharmacy.

RESULTS

All 4 subjects experienced a marked exacerbation of anxiety/panic and PTSD-specific symptoms immediately after ingesting yohimbine in a natural setting.

CONCLUSIONS

The response in these individuals closely resembled the response observed after IV yohimbine in combat veterans with PTSD. The present cases occurred in a natural setting and thus complement laboratory-based findings. The authors caution against the recreational or medical use of yohimbine in individuals who have PTSD.

Anniversary reactions in Gulf War veterans: a follow-up inquiry 6 years after the war

OBJECTIVE

The goal of this study was to assess the occurrence of anniversary reactions in Gulf War veterans 6 years after the conclusion of the war.

METHOD

Subjects were administered questionnaires and asked to identify specific months of best and worst functioning and months of least or most symptoms of posttraumatic stress disorder (PTSD) for the 12 months before the study. Months of negative experiences were compared with previously documented dates of exposure to traumatic events during the war. Similar reports were also obtained from the veterans' spouses in order to assess corroborative evidence for the occurrence of anniversary reactions.

RESULTS

Anniversary reactions occurred with a frequency greater than chance and most often in individuals exposed to a greater number of traumatic events. Overall, spouse reports matched the veterans' reports of anniversary reactions. In addition, spouses identified anniversary reactions that were not endorsed by their veterans.

CONCLUSIONS

These data suggest that anniversary reactions occur in numbers greater than those expected by chance, are correlated to the occurrence of traumatic events, and may be a part of the syndrome of PTSD.

Abnormal mismatch negativity in women with sexual assault-related posttraumatic stress disorder

BACKGROUND

Disturbances in sensory processing have been hypothesized in individuals with posttraumatic stress disorder (PTSD). The authors investigated this possibility by using mismatch negativity (MMN), an event-related potential (ERP) that reflects the operation of a preconscious cortical detector of stimulus change.

METHODS

Thirteen medication-free women with sexual assault-related PTSD were compared with 16 age-matched, healthy comparison women without PTSD. ERPs were elicited by regularly presented "standard" auditory stimuli and by infrequently occurring "deviant" auditory stimuli, which differed slightly in frequency. The MMN was identified in the subtraction waveforms as the difference between ERPs elicited by the deviant and standard stimuli. Group comparisons of P50, N1, P2, and N2 to the standard and to the deviant stimuli, and of the MMN in the subtraction waveform were performed.

RESULTS

The amplitude of the MMN was significantly greater in the PTSD compared to the non-PTSD women. MMN was significantly correlated with the total Mississippi PTSD Symptom Scale score in the PTSD group. No significant group differences were noted in P50, N1, or P2 responding. Significant group differences in N2 were due to the increased MMN in PTSD subjects.

CONCLUSIONS

The data provide evidence for abnormalities in preconscious auditory sensory memory in PTSD, whereas earlier studies have reported abnormalities in conscious processing. These data suggest an increased sensitivity to stimulus changes in PTSD and implicate the auditory cortex in the pathophysiology of the disorder.

Fear-potentiated startle conditioning to explicit and contextual cues in Gulf War veterans with posttraumatic stress disorder

Aversive conditioning to explicit and contextual cues was examined in Gulf War veterans with and without posttraumatic stress disorder (PTSD) by use of the startle reflex methodology. Veterans participated in a differential aversive conditioning experiment consisting of 2 sessions separated by 4 or 5 days. Each session comprised two startle habituation periods, a preconditioning phase, a conditioning phase, and a postconditioning extinction test. In contrast to the non-PTSD group, the PTSD group showed a lack of differential startle response in the presence of a conditioned stimulus with or without an unconditioned stimulus in Session 1 and an increase in the baseline startle response during Session 2. The PTSD group also exhibited normal differential conditioning following reconditioning in Session 2. These data suggest that individuals with PTSD tend to generalize fear across stimuli and are sensitized by stress.

Effects of experimental context and explicit threat cues on acoustic startle in Vietnam veterans with posttraumatic stress disorder

BACKGROUND

The hypothesis that exaggerated startle in Vietnam veterans with posttraumatic stress disorder (PTSD) reflects an anxiogenic response to stressful contexts was tested.

METHODS

Thirty-four nonmedicated Vietnam veterans with PTSD, and 17 combat and 14 civilian non-PTSD controls participated in two testing sessions over separate days. Acoustic startle stimuli were delivered alone or in a test of prepulse inhibition. In the first session, startle was assessed without experimental stress. In the second session, startle was investigated during a stressful "threat of shock" experiment, when subjects anticipated the administration of shocks during threat periods and during safe periods when no shocks were anticipated.

RESULTS

The magnitude of startle did not differ significantly among the three groups in the first session, but was increased throughout the threat of shock experiment in the PTSD veterans in the second session. The actual increase in startle in the threat compared to the safe condition did not significantly differ among the three groups. Prepulse inhibition was reduced in the PTSD veterans, compared to the non-PTSD civilians, but not compared to the non-PTSD veterans.

CONCLUSION

Exaggerated startle in Vietnam veterans with PTSD reflects an anxiogenic response to an environment that is experienced as stressful.

Effect of darkness on acoustic startle in Vietnam veterans with PTSD

OBJECTIVE

Exaggerated startle is a symptom of posttraumatic stress disorder (PTSD), but empirical studies have not consistently documented elevated baseline startle in PTSD. The authors proposed in a previous study that Vietnam veterans with PTSD exhibit exaggerated startle only under stressful conditions. They reported that darkness facilitated startle in humans, suggesting that the startle reflex is sensitive to the aversive nature of darkness. In the present study they tested the hypothesis that the magnitude of facilitation of startle by darkness would be greater in Vietnam veterans with PTSD than in comparison groups of subjects without PTSD. Prepulse inhibition was also investigated.

METHOD

The magnitude of startle and prepulse inhibition were assessed in alternating periods of darkness and light in 19 nonmedicated Vietnam veterans with PTSD, 13 Vietnam veterans without PTSD, and 20 civilians without PTSD.

RESULTS

The overall startle level was higher in the veterans with PTSD than in either of the two groups of subjects without PTSD. Startle was facilitated by darkness, and the magnitude of this facilitation was greater in the veterans with PTSD than in the civilians without PTSD, but it was not greater in the veterans without PTSD. Prepulse inhibition was not affected by darkness and did not significantly differ among groups.

CONCLUSIONS

Contrary to the hypothesis, elevated sensitivity to darkness was specific to individuals with combat experience, not to individuals with PTSD, perhaps because veterans had become aversively conditioned to darkness during their combat experiences. The more general increase in startle reactivity in the veterans with PTSD is consistent with clinical observations and descriptions of symptoms in DSM-IV.

Anniversary reactions in Gulf War veterans: a naturalistic inquiry 2 years after the Gulf War

The goal of this study was to assess the occurrence of anniversary reactions in Gulf War veterans 2 years after the conclusion of Operation Desert Storm. Subjects were administered questionnaires and asked to identify specific months of best and worst functioning, and months of least or most symptoms of posttraumatic stress disorder (PTSD). Negatively experienced months were compared to documented dates of exposure to traumatic events during the war. Anniversary reactions occurred with a frequency greater than chance and were seen most in individuals exposed to a greater number, and to more severe types, of traumatic events. This suggests that anniversary reactions are etiologically linked to traumatic events and may be a part of the syndrome of PTSD.

Noradrenergic and serotonergic function in posttraumatic stress disorder

BACKGROUND

Yohimbine hydrochloride produces marked behavioral and cardiovascular effects in combat veterans with posttraumatic stress disorder (PTSD). In the present study, yohimbine was used as a probe of noradrenergic activity, and meta-chlorophenylpiperazine (m-CPP) as a probe of serotonergic activity. To our knowledge, this is the first study to describe the behavioral and cardiovascular effects of meta-CPP in patients with PTSD, and to compare these effects with those of yohimbine.

METHOD

Twenty-six patients with PTSD and 14 healthy subjects each received an intravenous infusion of yohimbine hydrochloride (0.4 mg/kg), m-CPP (1.0 mg/kg), or saline solution on 3 separate test days in a randomized balanced order and in double-blind fashion. Behavioral and cardiovascular measurements were determined at multiple times.

RESULTS

Eleven (42%) of the patients with PTSD experienced yohimbine-induced panic attacks and had significantly greater increases compared with controls in anxiety, panic, and PTSD symptoms, but not in cardiovascular measurements. Eight patients (31%) with PTSD experienced m-CPP-induced panic attacks and had significantly greater increases compared with controls in anxiety, panic, and PTSD symptoms, and in standing diastolic blood pressure. Yohimbine-induced panic attacks tended to occur in different patients from m-CPP-induced panic attacks.

CONCLUSION

These data suggest the presence of 2 neurobiological subgroups of patients with PTSD, one with a sensitized noradrenergic system, and the other with a sensitized serotonergic system.

Startle reflex abnormalities in women with sexual assault-related posttraumatic stress disorder

OBJECTIVE

This investigation was designed to assess the acoustic startle response in treatment-seeking women with sexual assault-related posttraumatic stress disorder (PTSD).

METHOD

Thirteen patients with sexual assault-related PTSD and 16 healthy female comparison subjects were recruited for participation in the study. Each patient met the full criteria for PTSD according to the Structured Clinical Interview for DSM-III-R. All subjects in the study were right-handed. The acoustic stimuli were bursts of white noise (92 dB and 102 dB) with a nearly instantaneous onset delivered binaurally through headphones.

RESULTS

The magnitude of the startle response (eye blink) to the first stimulus was asymmetrically distributed in the PTSD patients but not in the comparison subjects: it was greater for the left eye than the right eye in the PTSD patients only. There was a differential asymmetry of startle response in the two subgroups of patients (recent PTSD and long-standing PTSD): the startle reflex was larger for the left eye than the right in the subgroup with recent PTSD but not in the group with long-standing PTSD.

CONCLUSIONS

This study provides the first objective evidence of startle abnormalities in women with PTSD. The significantly greater startle responses for the left eye compared with the right in the PTSD subjects suggest a laterality effect. As suggested by the preclinical model of shock sensitization, it is possible that in a subgroup of individuals with PTSD, trauma may sensitize the startle reflex. This model may hold true in humans and is supported by the findings of greater startle response in the patients with recent-onset PTSD.

Evidence of acoustic startle hyperreflexia in recently detoxified early onset male alcoholics: modulation by yohimbine and m-chlorophenylpiperazine (mCPP)

Preclinical studies suggest that acoustic startle amplitude is increased during ethanol withdrawal. The current study evaluated the effects of intravenous infusion of the alpha 2-adrenergic antagonist, yohimbine (0.4 mg/kg), the serotonin partial agonist m-chlorophenylpiperazine (mCPP, 0.1 mg/kg), and placebo administered to 22 male patients meeting DSM-III-R criteria for alcohol dependence and 13 male healthy subjects. Patients and healthy subjects completed 3 test days under double-blind conditions in a randomized order. Patients were sober for 12-26 days prior to testing. On each test day, participants completed startle testing 80 min following drug infusion. Stimuli with varying intensities (90, 96, 102, 108, 114 dB) were presented in a randomized order balanced across four blocks. Stimuli consisted of 40-ms bursts of white noise administered every 45-60 s for 15-20 min through headphones. Analyses indicated that patients exhibited elevated acoustic startle magnitudes on the placebo day relative to healthy subjects. In patients, the magnitude of startle amplitudes elicited at 90 dB, but not 114 dB, correlated significantly with the number of previous alcohol detoxifications. Yohimbine increased startle magnitudes and reduced startle latencies relative to placebo and mCPP in both patients and healthy subjects. mCPP did not alter startle magnitude in either group. Yohimbine also increased the probability that a 90-dB stimulus produced a startle response in healthy subjects, but not in patients. Blunting of yohimbine effects on startle probability may reflect the baseline elevations in startle probability levels in patients, but may also be consistent with other evidence of reduced postsynaptic, but not presynaptic, noradrenergic function in these same patients. These data replicate and extend previous reports indicating that yohimbine facilitates the acoustic startle response in humans. They also further implicate the number of episodes of ethanol withdrawal as a factor influencing subsequent neurobiological responsivity in chronic alcoholic patients. Based on the current data, future research should explore whether measurement of the acoustic startle response provides an objective quantitative severity measure of ethanol withdrawal.

Consistency of memory for combat-related traumatic events in veterans of Operation Desert Storm

OBJECTIVE

The nature of traumatic memories is currently the subject of intense scientific investigation. While some researchers have described traumatic memory as fixed and indelible, others have found it to be malleable and subject to substantial alteration. The current study is a prospective investigation of memory for serious combat-related traumatic events in veterans of Operation Desert Storm.

METHOD

Fifty-nine National Guard reservists from two separate units completed a 19-item trauma questionnaire about their combat experiences 1 month and 2 years after their return from the Gulf War. Responses were compared for consistency between the two time points and correlated with level of symptoms of posttraumatic stress disorder (PTSD).

RESULTS

There were many instances of inconsistent recall for events that were objective and highly traumatic in nature. Eighty-eight percent of subjects changed their responses on at least one of the 19 items, while 61% changed two or more items. There was a significant positive correlation between score on the Mississippi Scale for Combat-Related Posttraumatic Stress Disorder at 2 years and the number of responses on the trauma questionnaire changed from no at 1 month to yes at 2 years.

CONCLUSIONS

These findings do not support the position that traumatic memories are fixed or indelible. Further, the data suggest that as PTSD symptoms increase, so does amplification of memory for traumatic events. This study raises questions about the accuracy of recall for traumatic events, as well as about the well-established but retrospectively determined relationship between level of exposure to trauma and degree of PTSD symptoms.

Baseline startle amplitude and prepulse inhibition in Vietnam veterans with posttraumatic stress disorder

Although an exaggerated startle response is a symptom of posttraumatic stress disorder (PTSD), empirical support for elevated baseline startle in PTSD has been weak. The present study investigated the eyeblink component of the acoustic startle reflex and prepulse inhibition (PPI) in 21 unmedicated Vietnam veterans with PTSD and in 17 civilian and 10 combat veteran comparison subjects. Patients with PTSD exhibited normal acoustic startle amplitude, but showed a significant reduction in PPI relative to the civilian subjects. There was only a trend toward a reduction in PPI in the PTSD group compared with the combat control group. The study does not support the hypothesis of exaggerated baseline startle in Vietnam veterans with PTSD but suggests abnormal startle modulation by a prepulse (i.e., PPI). Discrepancies between studies concerning the amplitude of startle in PTSD are discussed.