Diminished acoustic startle in chronic cocaine users

Reduced amplitude and slowed latency of the acoustic startle response in adolescents and adults with 22q11.2 deletion syndrome

BACKGROUND

22q11.2 deletion syndrome (22q11DS) is one of the most robust genetic predictors of psychosis and other psychiatric illnesses. In this study, we examined 22q11DS subjects' acoustic startle responses (ASRs), which putatively index psychosis risk. Latency of the ASR is a presumptive marker of neural processing speed and is prolonged (slower) in schizophrenia. ASR measures correlate with increased psychosis risk, depend on glutamate and dopamine receptor signaling, and could serve as translational biomarkers in interventions for groups at high psychosis risk.

METHODS

Startle magnitude, latency, and prepulse inhibition were assessed with a standard acoustic startle paradigm in 31 individuals with 22q11.2DS and 32 healthy comparison (HC) subjects. Surface electrodes placed on participants' orbicularis oculi recorded the electromyographic signal in ASR eyeblinks. Individuals without measurable startle blinks in the initial habituation block were classified as non-startlers.

RESULTS

Across the startle session, the ASR magnitude was significantly lower in 22q11DS subjects than HCs because a significantly higher proportion of 22q11DS subjects were non-startlers. Latency of the ASR to pulse-alone stimuli was significantly slower in 22q11DS than HC subjects. Due to the overall lower 22q11DS startle response frequency and magnitudes prepulse inhibition could not be analyzed.

CONCLUSIONS

Reduced magnitude and slow latency of 22q11DS subjects' responses suggest reduced central nervous system and neuronal responsiveness. These findings are consistent with significant cognitive impairments observed in 22q11DS subjects. Further research is needed to untangle the connections among basic neurotransmission dysfunction, psychophysiological responsiveness, and cognitive impairment.

Prepulse inhibition deficit as a transdiagnostic process in neuropsychiatric disorders: a systematic review

BACKGROUND

Psychopathological research is moving from a specific approach towards transdiagnosis through the analysis of processes that appear transversally to multiple pathologies. A phenomenon disrupted in several disorders is prepulse inhibition (PPI) of the startle response, in which startle to an intense sensory stimulus, or pulse, is reduced if a weak stimulus, or prepulse, is previously presented.

OBJECTIVE AND METHODS

The present systematic review analyzed the role of PPI deficit as a possible transdiagnostic process for four main groups of neuropsychiatric disorders: (1) trauma-, stress-, and anxiety-related disorders (2) mood-related disorders, (3) neurocognitive disorders, and (4) other disorders such as obsessive-compulsive, tic-related, and substance use disorders. We used Web of Science, PubMed and PsycInfo databases to search for experimental case-control articles that were analyzed both qualitatively and based on their potential risk of bias. A total of 64 studies were included in this systematic review. Protocol was submitted prospectively to PROSPERO 04/30/2022 (CRD42022322031).

RESULTS AND CONCLUSION

The results showed a general PPI deficit in the diagnostic groups mentioned, with associated deficits in the dopaminergic neurotransmission system, several areas implied such as the medial prefrontal cortex or the amygdala, and related variables such as cognitive deficits and anxiety symptoms. It can be concluded that the PPI deficit appears across most of the neuropsychiatric disorders examined, and it could be considered as a relevant measure in translational research for the early detection of such disorders.

Sensorimotor Gating in Cocaine-Related Disorder with Comorbid Schizophrenia or Antisocial Personality Disorder

Objective: Schizophrenia, cocaine-related disorder, antisocial personality disorder, and psychopathy share biological bases, but few studies discriminate between these disorders by means of prepulse inhibition. This work studies the phenotype of patients with cocaine-related disorders who are vulnerable to presenting a dual diagnosis of schizophrenia or antisocial personality disorder, by evaluating their prepulse inhibition, impulsivity and psychopathy personality traits. Methods: The sample (n = 38) was divided into three groups: (1) cocaine-related disorder (8 individuals diagnosed with cocaine-related disorder who did not present any other mental disorder), (2) cocaine-related disorder and schizophrenia (n = 14), and (3) cocaine-related disorder and antisocial personality disorder (n = 16). Results: The prepulse inhibition in the two groups with dual diagnosis was lower than that in the cocaine-related disorder group, F(2, 35) = 6.52, p = .004, while there was no significant differences between the two dual-diagnosis groups. Psychopathy was evaluated with the revised Hare Psychopathy Checklist and showed no correlation with the prepulse inhibition. Secondary psychopathy (impulsivity and poor behavior control), as evaluated with Levenson Self-Report Psychopathy Scale, was related to the prepulse inhibition. Two discriminating functions were obtained that allowed prediction of patient inclusion in the groups using the prepulse inhibition and the revised Hare Psychopathy Checklist with a success rate of 81.6% (cocaine-related disorder = 62.5%; cocaine-related disorder and schizophrenia = 78.6%; cocaine-related disorder and antisocial personality disorder = 93.8%). These results are discussed in regard to the neurobiological implications of prepulse inhibition in dual diagnosis. Conclusions: The results suggest that the prepulse inhibition is a promising dual-diagnosis vulnerability marker in individuals with cocaine addiction, because prepulse inhibition deficits are related both to schizophrenia and antisocial personality disorder. In addition, prepulse inhibition, which is considered a good endophenotype for studies on the genetic and neurobiological basis of cocaine-related disorder and schizophrenia, could be used in the same way in studies on antisocial personality disorder.

Baseline prepulse inhibition of the startle reflex predicts the sensitivity to the conditioned rewarding effects of cocaine in male and female mice

RATIONALE

Prepulse inhibition (PPI) of the startle reflex is a model of pre-attentional inhibitory function. The dopamine baseline in the nucleus accumbens plays a key role in PPI regulation as well as in the rewarding effects of cocaine.

OBJECTIVES

The aim of this study was to evaluate the predictive ability of PPI to identify the more vulnerable mice of both sexes to the conditioned rewarding effects of cocaine.

METHODS

Male and female OF1 mice were first tested in the PPI paradigm to classify them as high or low PPI. Afterwards, they were evaluated in the conditioned place preference (CPP) paradigm induced by cocaine (1, 6 and 12 mg/kg). Moreover, the D1R and D2R protein expressions in the striatum of high and low PPI animals were analysed by Western blot.

RESULTS

Only high-PPI mice acquired CPP induced by low doses of cocaine (1 and 6 mg/kg), while the low-PPI mice needed a higher dose of cocaine (12 mg/kg) to acquire the CPP, but once mice were conditioned, males did not extinguish the conditioned preference and females reinstated the preference with lower doses of cocaine than their control counterparts. Low-PPI animals, especially females, showed higher basal levels of D2R than those with a higher PPI.

CONCLUSIONS

Low-PPI mice presented a lower sensitivity to the conditioned rewarding effects of cocaine, but once they were conditioned with a higher dose, they displayed a stronger, perseverant conditioned preference. The predictive capacity of PPI to detect the more vulnerable mice to the conditioned effects of cocaine is discussed.

Relationship between Toxoplasma gondii seropositivity and acoustic startle response in an inner-city population

Toxoplasma gondii (TOXO) is a neuroinvasive protozoan parasite that induces the formation of persistent cysts in mammalian brains. It infects approximately 1.1million people in the United States annually. Latent TOXO infection is implicated in the etiology of psychiatric disorders, especially schizophrenia (SCZ), and has been correlated with modestly impaired cognition. The acoustic startle response (ASR) is a reflex seen in all mammals. It is mediated by a simple subcortical circuit, and provides an indicator of neural function. We previously reported the association of TOXO with slowed acoustic startle latency, an index of neural processing speed, in a sample of schizophrenia and healthy control subjects. The alterations in neurobiology with TOXO latent infection may not be specific to schizophrenia. Therefore we examined TOXO in relation to acoustic startle in an urban, predominately African American, population with mixed psychiatric diagnoses, and healthy controls. Physiological and diagnostic data along with blood samples were collected from 364 outpatients treated at an inner-city hospital. TOXO status was determined with an ELISA assay for TOXO-specific IgG. A discrete titer was calculated based on standard cut-points as an indicator of seropositivity, and the TOXO-specific IgG concentration served as serointensity. A series of linear regression models were used to assess the association of TOXO seropositivity and serointensity with ASR magnitude and latency in models adjusting for demographics and psychiatric diagnoses (PTSD, major depression, schizophrenia, psychosis, substance abuse). ASR magnitude was 11.5% higher in TOXO seropositive subjects compared to seronegative individuals (p=0.01). This effect was more pronounced in models with TOXO serointensity that adjusted for sociodemographic covariates (F=7.41, p=0.0068; F=10.05, p=0.0017), and remained significant when psychiatric diagnoses were stepped into the models. TOXO showed no association with startle latency (t=0.49, p=0.63) in an unadjusted model, nor was TOXO associated with latency in models that included demographic factors. After stepping in individual psychiatric disorders, we found a significant association of latency with a diagnosis of PTSD (F=5.15, p=0.024), but no other psychiatric diagnoses, such that subjects with PTSD had longer startle latency. The mechanism by which TOXO infection is associated with high startle magnitude is not known, but possible mechanisms include TOXO cyst burden in the brain, parasite recrudescence, or molecular mimicry of a host epitope by TOXO. Future studies will focus on the neurobiology underlying the effects of latent TOXO infection as a potential inroad to the development of novel treatment targets for psychiatric disease.

Low startle magnitude may be a behavioral marker of vulnerability to cocaine addiction

Cocaine addicted men have low startle magnitude persisting during prolonged abstinence. Low startle rats show greater cocaine self-administration than high startle rats. Low startle may be a marker of a vulnerability to heightened cocaine-related behaviors in rats and similarly may be a marker of vulnerability to cocaine addiction in humans.

Selective developmental alterations in The HIV-1 transgenic rat: Opportunities for diagnosis of pediatric HIV-1

Since the advent of combination antiretroviral therapy (cART), pediatric HIV-1 (PHIV) has evolved from a fatal disease to a chronic disease as children perinatally infected with HIV-1 survive into adulthood. The HIV-1 transgenic (Tg) rat, which expresses 7 of the 9 HIV-1 genes constitutively throughout development, was used to model the early development of chronic neurological impairment in PHIV. Male and female Fischer HIV-1 Tg and F344 N control rats, sampled from 35 litters, were repeatedly assessed during early development using multiple experimental paradigms, including somatic growth, locomotor activity, cross-modal prepulse inhibition (PPI) and gap-prepulse inhibition (gap-PPI). Later eye opening was observed in HIV-1 Tg animals relative to controls. HIV-1 Tg animals exhibited a shift in the development of locomotor activity implicating alterations in the maturation of the forebrain cholinergic inhibitory system. Alterations in the development of PPI and perceptual sharpening were observed in both auditory and visual PPI as indexed by a relative insensitivity to the dimension of time (msec for ISI; days of age for perceptual sharpening) as a function of the HIV-1 transgene. Presence of the HIV-1 transgene was diagnosed with 97.1 % accuracy using auditory and visual PPI measurements from PD 17 and 21. Early selective developmental alterations observed in the HIV-1 Tg rats provide an opportunity for the development of a point-of-care screening tool, which would permit the early diagnosis of PHIV and improve the long-term outcome for children perinatally infected with HIV-1.

Prepulse inhibition in psychiatric disorders--apart from schizophrenia

Prepulse inhibition (PPI) is a robust operational measure of sensorimotor gating. In schizophrenic patients PPI is deficient. The aim of our review was to investigate the state of science regarding PPI and psychiatric disorders aside from schizophrenia. We used the online database PubMed in order to search for original published reports on PPI studies. The terms "prepulse inhibition", "sensorimotor gating", "blink recovery", and "blink reflex excitability" have been combined with the names of psychiatric disorders. We found that PPI is deficient in obsessive compulsive disorder (OCD) and Gilles de la Tourette's syndrome (GTS). In bipolar disorder dysfunctional PPI seems to be rather state dependent. Studies on depression and attention deficit/hyperactivity disorder (ADHD) consistently report no alterations. Evidence regarding sensorimotor gating in anxiety, autism, fragile X syndrome, posttraumatic stress disorder (PTSD), substance disorders, and Huntington's disease is still poor. There is a strong need for further studies on PPI in psychiatric disorders. PPI is highly applicable for translational research and might also be a very useful tool to investigate the mode of action of innovative, neuro-modulative techniques. Future PPI studies should control for influencing variables such as smoking, sex, or medication.

Increased sensorimotor gating in recreational and dependent cocaine users is modulated by craving and attention-deficit/hyperactivity disorder symptoms

BACKGROUND

Cocaine dependence has been associated with blunted dopamine and norepinephrine signaling, but it is unknown if recreational cocaine use is also associated with alterations of catecholamine systems. Prepulse inhibition (PPI) of the acoustic startle response-a measure of sensorimotor gating-is highly sensitive for manipulations of the catecholamine system. Therefore, we investigated whether relatively pure recreational users (RCU) and dependent cocaine users (DCU) display alterations of PPI, startle reactivity, and habituation. Moreover, the influences of methylenedioxymethamphetamine and cannabis co-use, craving, and attention-deficit/hyperactivity disorder (ADHD) symptoms on startle measures were examined.

METHODS

In 64 RCU, 29 DCU, and 66 stimulant-naïve control subjects, PPI of acoustic startle response, startle reactivity, habituation, ADHD symptoms, and cocaine craving were assessed. Drug use of all participants was controlled by hair and urine toxicologies.

RESULTS

Both RCU and DCU showed increased PPI in comparison with control participants (Cohen's d=.38 and d=.67, respectively), while RCU and DCU did not differ in PPI measures (d=.12). No significant group differences were found in startle reactivity or habituation measures. In cocaine users, PPI was positively correlated with cumulative cocaine dose used, craving for cocaine, and ADHD symptoms. Users with a diagnosis of ADHD and strong craving symptoms displayed the highest PPI levels compared with control subjects (d=.78).

CONCLUSIONS

The augmented PPI in RCU and DCU suggests that recreational use of cocaine is associated with altered catecholamine signaling, in particular if ADHD or craving symptoms are present. Finally, ADHD might be a critical risk factor for cocaine-induced changes of the catecholamine system.

Acoustic startle reduction in cocaine dependence persists for 1 year of abstinence

RATIONALE

Chronic cocaine use results in long-lasting neurochemical changes that persist beyond the acute withdrawal period. Previous work from our group reported a profound reduction in the acoustic startle response (ASR) in chronic cocaine-dependent subjects in early abstinence compared to healthy controls that may be related to long-lasting neuroadaptations following withdrawal from chronic cocaine use.

OBJECTIVES

This study aims to investigate the persistence and time course of the decrements in the ASR of cocaine-dependent subjects during prolonged abstinence.

METHODS

Seventy-six cocaine-dependent (COC) subjects and 30 controls (CONT) were tested, the former after a period of heavy cocaine dependence. COC subjects were retested sequentially for 1 year of abstinence or until relapse. ASR testing was conducted at 3-dB levels and the eye-blink component of the startle response was quantified with electromyographic recording of the orbicularis oculi muscle.

RESULTS

While there was no difference in startle magnitude between CONT and COC in early abstinence, by day 40 of abstinence COC subjects exhibited a statistically significant decline (p = 0.0057) in ASR magnitude as compared with CONT and this decrement persisted for up to 1 year of abstinence (p = 0.0165). In addition, startle latency was slower in COC subjects as compared with CONT at all stages of abstinence.

CONCLUSIONS

These results replicate and expand upon the earlier finding that chronic cocaine use impairs the ASR in a manner that persists beyond the acute withdrawal period. This phenomenon may represent a biological measure of long-term neural changes accompanying cocaine dependence and subsequent withdrawal.

Effects of cocaine self-administration history under limited and extended access conditions on in vivo striatal dopamine neurochemistry and acoustic startle in rhesus monkeys

RATIONALE

The transition from infrequent and controlled cocaine use to dependence may involve enduring changes in neurobiology as a consequence of persistent drug use.

OBJECTIVE

The present study utilized an intravenous drug self-administration protocol of increasing cocaine access to evaluate potential changes in dopamine function in vivo, including changes in sensitivity to psychostimulants.

MATERIALS AND METHODS

Drug-naïve rhesus monkeys were provided limited access (1 h) to cocaine self-administration for 60 days followed by 60 days under an extended access condition (4 h). Basal levels of striatal extracellular dopamine and its metabolites, as well as the effectiveness of cocaine and amphetamine to elevate dopamine, were determined with in vivo microdialysis before the initiation of cocaine self-administration and during limited and extended access. The effect of cocaine and amphetamine on the acoustic startle response was also examined to assess complementary behavioral changes as a function of drug history.

RESULTS

Extended access to cocaine self-administration lead to increased daily intake compared to limited access conditions but did not result in escalated intake over time. However, cocaine- and amphetamine-induced increases in striatal dopamine were diminished as a function of cocaine self-administration history. Surprisingly, there was no effect of drug-taking history on sensitivity to psychostimulant-induced enhancement of startle amplitude.

CONCLUSIONS

The present experiments provide evidence of a hypofunctional dopamine system that is not associated with an escalation in drug intake or reflected in measures of acoustic startle.

Defizite der sensomotorischen Filterleistung bei psychiatrischen Erkrankungen

Die Präpuls-Inhibition (PPI) des akustischen Schreckreflexes gilt als operationales Maß für einen teils vorbewußten attentionalen Filterprozeß, der auch als sensomotorisches Gating bezeichnet wird. Die PPI wird durch ein cortico-striato-pallido-pontines (CSPP) Netzwerk reguliert, welches frontale und mediotemporale Hirnareale, das ventrale Striatum, das ventrale Pallidum und pontine Bereiche des Hirnstamms mit einbezieht. Verschiedene psychiatrische und neurologische Erkrankungen zeigen beeinträchtigte Gating-Prozesse, doch insbesondere die konsistenten Befunde eines PPI-Defizits in der Schizophrenie haben dazu beigetragen, daß die Schizophrenie heute auch als Filterstörung verstanden wird. Die PPI hat sich mittlerweile als translationales Modell für gestörte Filterprozesse in der Schizophrenie etabliert, da sie bei verschiedenen Versuchstieren abgeleitet werden kann und pharmakologisch manipulierbar ist. Darüber hinaus wurde die PPI als vielversprechender Endophänotyp, d. h. als Gen-naher biologischer Marker, der Schizophrenie vorgeschlagen. Man erhofft sich von der Identifizierung solcher Endophänotypen eine verbesserte Entschlüsselung der krankheitsmitverursachenden Gene im Vergleich zu bislang nicht zielführenden genetischen Assoziationsstudien mit den komplexeren Krankheitsphänotypen. Des Weiteren wird die Korrektur künstlich erzeugter PPI-Defizite bei Versuchstieren als Modell für antipsychotische Wirksamkeit neu entwickelter Substanzen zur Behandlung der Schizophrenie genutzt. Der vorliegende Artikel soll einen Überblick über die Anwendungsmöglichkeiten und Grenzen des PPI-Paradigmas in der klinischen und grundlagenorientierten psychologischen und psychiatrischen Forschung geben.

Sex differences in negative affective response during nicotine withdrawal

This study examined physiological indicants of the neurobiological mediators of negative affect during acute nicotine withdrawal. Eighty subjects (41 male) were assigned to one of four groups (24-h deprived or nondeprived dependent smokers, occasional smokers, and nonsmokers) and participated in an instructed fear conditioning paradigm involving cued administration of electric shock. Negative affective response was measured with fear-potentiated startle during cues that signaled electric shock and during the postcue offset recovery period. Salivary cortisol and self-report measures were also collected. Fear-potentiated startle results indicated that affective recovery postcue offset was delayed in nicotine-deprived women. Nicotine-deprived women also displayed elevated cortisol levels throughout the fear conditioning procedure.

Prepulse inhibition during withdrawal from an escalating dosage schedule of amphetamine

RATIONALE

Psychomotor stimulants can induce psychotic states in humans that closely resemble those observed in patients with idiopathic schizophrenia. Attentional and sensorimotor gating impairments are observed in schizophrenic patients using the latent inhibition (LI) and prepulse inhibition (PPI) behavioral assays, respectively. Our previous studies demonstrated that after 4 days of withdrawal from a period of amphetamine (AMPH) administration, animals exhibited disrupted LI but normal PPI.

OBJECTIVE

The aim of the present study was to test PPI in AMPH-withdrawn rats under experimental conditions similar to those used to best demonstrate locomotor sensitization following AMPH withdrawal.

METHODS

We examined the effects on PPI of (1) pairing drug injections with PPI test-associated cues, (2) administration of a low-dose dopamine agonist challenge and (3) testing following longer withdrawal periods (23, 30, 60 days).

RESULTS

Although none of these conditions revealed a disruption of PPI in AMPH-withdrawn rats, we did observe that the acoustic startle response was reduced during a restricted time period following AMPH withdrawal. Similar to our previous findings, AMPH-withdrawn animals showed disrupted LI on day 16 of withdrawal and locomotor sensitization to a challenge injection of AMPH after 62 days of withdrawal.

CONCLUSION

We conclude that the effects of repeated AMPH on PPI are not modulated by the same experimental parameters known to be important for eliciting locomotor sensitization and that withdrawal from the schedule of AMPH administration used in this study models only specific cognitive dysfunctions linked to schizophrenic symptoms, since LI was disrupted but PPI was not affected.

Prepulse inhibition of the acoustic startle response in cocaine-withdrawn rats

Prepulse inhibition (PPI) of startle is a sensorimotor gating task in which a low-intensity acoustic stimulus presented prior to a high-intensity, startle-eliciting stimulus can attenuate the acoustic startle response (ASR). Previous studies on startle reactivity in cocaine-withdrawn rats have found minimal changes; the present study extends this work to the gating of ASR. In Experiment 1, rats were injected daily with either saline or cocaine (30 mg/kg i.p.) for 2 weeks. ASR and PPI were measured prior to, and at 3- and 14-day withdrawal from, the chronic treatment. No effect of cocaine treatment was found on either measure. In Experiment 2, treatment was extended to 8 weeks, and an earlier withdrawal time point (1 day) was added. Rats treated with cocaine for 8 weeks exhibited lower startle reactivity during withdrawal compared with saline-treated controls. PPI did not differ between treatment groups. Thus, extended chronic treatment with cocaine rendered significant effects on startle responsivity. Further, this finding mirrors the blunted ASR exhibited in chronic cocaine users [Neuropsychopharmacology 22 (2000) 89.].

Animal models of deficient sensorimotor gating: what we know, what we think we know, and what we hope to know soon

Sensorimotor gating of the startle reflex can be studied in humans and laboratory animals using measures of prepulse inhibition (PPI) of the startle reflex. PPI is reduced in patients with specific neuropsychiatric disorders and in rats after manipulation of the limbic cortex, striatum, pallidum or pontine tegmentum. Studies are rapidly identifying the neurochemical and neuroanatomical substrates regulating PPI in laboratory animals; this detailed circuit information has been used as a 'blueprint' to identify possible candidate substrates responsible for PPI deficits in psychiatrically disordered humans. In parallel, studies have also begun to assess the homology of pharmacological effects on PPI across species, as an initial step towards translating detailed neural circuit information from rats to humans. Despite this rapid progress, there is an increasing danger of overlooking important methodological and interpretative issues that could impact either positively or negatively on the ultimate utility of models based on measures of PPI. Some of these issues--ranging from the cross-species methods for quantifying specific variables to the relevance of genetic drift to animal and human studies of PPI--and their implications for future studies are the focus of this review.