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Psychopharmacology Jun 2022Prepulse inhibition (PPI) of startle is a sensorimotor gating phenomenon perturbed in a variety of neuropsychiatric conditions. Psychedelics disrupt PPI in rats and...
BACKGROUND
Prepulse inhibition (PPI) of startle is a sensorimotor gating phenomenon perturbed in a variety of neuropsychiatric conditions. Psychedelics disrupt PPI in rats and humans, but their effects and involvement of the serotonin 5-HT receptor (5-HTR) in mice remain unexplored.
METHODS
We tested the effect of the psychedelic 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) (0.5 mg/kg, i.p.) on startle amplitude and %PPI in response to acoustic stimuli under up to four different experimental conditions that included changes in background and stimulus intensity, prepulse and pulse duration, and interstimulus interval in male and female 129S6/SvEv mice. We also evaluated the effect of the 5-HTR antagonist M100,907 (1 mg/kg, i.p.) on DOI-induced startle amplitude and %PPI, as well as the effect of the psychedelic LSD (0.24 mg/kg, i.p.) and the dopamine agonists apomorphine (5 mg/kg, s.c.) and SKF-82,958 (0.5 mg/kg, i.p.) in male 129S6/SvEv mice.
RESULTS
DOI altered startle amplitude with either pulse alone or prepulse + pulse presentations in all PPI conditions, and increased %PPI in three out of four PPI conditions in male mice - an effect that was prevented by M100,907. In female mice, DOI increased %PPI without affecting startle amplitude. %PPI was positively correlated with startle amplitude in males while being negatively correlated in female mice. In male mice, LSD also increased %PPI, although it did not affect startle amplitude, whereas apomorphine and SKF-82,958 induced decreases in %PPI.
CONCLUSION
Our findings highlight a distinct effect of the psychedelic DOI on PPI in 129S6/SvEv mice, suggesting 5-HTR-dependent PPI improvement in a paradigm-dependent and sex-dependent manner.
Topics: Acoustic Stimulation; Animals; Apomorphine; Female; Hallucinogens; Lysergic Acid Diethylamide; Male; Mice; Prepulse Inhibition; Rats; Reflex, Startle; Serotonin
PubMed: 34345931
DOI: 10.1007/s00213-021-05913-9 -
Psychological Research Feb 2020The current research was designed to assess possible differences in the emotional content of pleasant and unpleasant face emoji using acoustically evoked eyeblink...
The current research was designed to assess possible differences in the emotional content of pleasant and unpleasant face emoji using acoustically evoked eyeblink startle reflex response. Stimuli were selected from Emojipedia Webpage. First, we assessed these stimuli with a previous independent sample of 190 undergraduate students (46 males and 144 females) mean age of 21.43 years (SD 3.89). A principal axis method was performed using the 30 selected emoji faces, extracting two factors (15 pleasant and 15 unpleasant emoji). Second, we measured the acoustic startle reflex modulation in 53 young adult women [mean age 22.13 years (SD 4.3)] during the viewing of each of the 30 emoji emotional faces in the context of the theory of motivation and emotion proposed by Lang (1995), but considering only the valence dimension. We expected to find higher acoustically evoked startle responses when viewing unpleasant emoji and lower responses for pleasant ones, similarly to the results obtained in the studies using human faces as emotional stimulus. An ANOVA was conducted to compare acoustic startle responses associated with pleasant and unpleasant emoji. Results yielded main effects for picture valence (λ = 0.80, F(1, 50) = 12.80, p = .001, η = 0.20). Post-hoc t test analysis indicated significant differences in the startle response between unpleasant (50.95 ± 1.75) and pleasant (49.14 ± 2.49) emoji (t (52) = 3.59, p = .001), with a Cohen's d = 0.495. Viewing affective facial emoji expressions modulates the acoustic startle reflex response according to their emotional content.
Topics: Adult; Blinking; Emotions; Female; Humans; Photic Stimulation; Reflex, Startle; Social Media; Spain; Young Adult
PubMed: 29455232
DOI: 10.1007/s00426-018-0991-x -
Biological Psychology Oct 2021We tested whether surprise elicits similar physiological changes as those associated with orienting and freezing after threat, as surprise also involves a state of...
We tested whether surprise elicits similar physiological changes as those associated with orienting and freezing after threat, as surprise also involves a state of interruption and attention for effective action. Moreover, because surprise is primarily driven by the unexpectedness of an event, initial physiological responses were predicted to be similar for positive, neutral, and negative surprises. Results of repetition-change studies (4 + 1 in Supplemental Materials) showed that surprise lowers heart rate (Experiments 1-4) and increases blood pressure (Experiment 4). No effects on body movement (Experiment 2) or finger temperature (Experiment 4) were found. When unexpected stimuli were presented more often (making them less surprising) heart rate returned to baseline, while blood pressure remained high (Experiment 4). These effects were not influenced by stimulus valence. However, second-to-second analyses within the first (surprising) block showed a tendency for a stronger increase in systolic blood pressure after negative vs. positive surprise.
Topics: Humans; Physiological Phenomena; Reflex, Startle
PubMed: 34453984
DOI: 10.1016/j.biopsycho.2021.108174 -
Physiology & Behavior Oct 2020There are indications that exposing adolescent rodents to oxytocin (OT) promotes social activity and reduces anxiety in adulthood. Adult male gray rats selected for...
There are indications that exposing adolescent rodents to oxytocin (OT) promotes social activity and reduces anxiety in adulthood. Adult male gray rats selected for elimination and enhancement of the aggressive response to humans, when exposed to OT, showed divergent changes in the resident behavior towards the intruder. It could be assumed that adolescent administration of both OT and antagonist of OT receptor (OTR) would also have different long-term effects on resident behavior and startle reflex in adult aggressive and tame rats. The aim of this work is to study the long-term effects of adolescent administration of both OT and antagonist of OT receptor (OTR) on resident behavior and startle reflex in adult tame and aggressive male gray rats. Starting at the age of 28 days, the animals received nasal applications of 5 μL of oxytocin solution (1 μg / μL) or saline for 5 days (daily). At the age of two months, the acoustic startle amplitude was assessed in two series of 5 acoustic stimuli. The resident-intruder test was performed one week later. Antagonist of OT receptor l-368,899 was administered intraperitoneally (i.p.) once at a dose of 5 mg/kg at the age of 30-33 days. Subsequent startle reflex tests were performed 20 days later, at the age of 50-53 days. A week later, the resident-intruder test was performed on the same rats. The startle amplitude in aggressive rats of the control group (in two series of acoustic stimuli) and those having received saline (in the first series) was larger than in the corresponding tame groups. Oxytocin and saline solutions did not significantly affect the startle amplitude compared to control animals. After saline administration, the attack latency in tame rats was longer than in aggressive rats (P <0.05). Oxytocin treatment caused a prolongation of this period in aggressive males compared with control animals receiving saline solution (P <0.01). In addition, oxytocin administration in aggressive males caused an increase in the time of social behavior, which did not include aggressive and same-sex behavior, as compared with the corresponding control animals (P <0.05). Exogenous oxytocin receptor antagonist (l-368,899) did not affect the startle amplitude and behavior in the resident-intruder test in aggressive and tame male rats. Adolescent OT treatment causes a prolongation of both the attack latency and social behavior in the resident-intruder test in adult aggressive male rats, but does not affect these parameters in tame rats.
Topics: Aggression; Animals; Male; Oxytocin; Rats; Receptors, Oxytocin; Reflex, Startle; Social Behavior
PubMed: 32619528
DOI: 10.1016/j.physbeh.2020.113046 -
Behavioural Processes Apr 2022The acoustic startle response and prepulse inhibition (PPI) of startle are measures related to information processing, which is impaired in schizophrenia. Some studies...
The acoustic startle response and prepulse inhibition (PPI) of startle are measures related to information processing, which is impaired in schizophrenia. Some studies have provided inconclusive patterns of association between both measures in rodents. We assessed the influence of baseline startle response on PPI in large samples of Roman high-(RHA) and low-avoidance (RLA) rat strains and in genetically heterogeneous stock (HS) rats. Results show that RHAs exhibit a PPI deficit compared to RLA rats, which is present regardless of the startle response levels. HS rats were stratified in two sub-samples according to their high or low PPI (HS-highPPI or HS-lowPPI, respectively) scores, and then they were grouped by their differential baseline startle amplitude (high reactivity -HR- or low reactivity -LR-) within each sub-sample. Differences between high- and low-PPI-stratified HS rats remained regardless of their high or low startle amplitude scores. Thus, the impairments in %PPI found in both RHA and HS-LowPPI rats are present irrespective of the relatively high or low levels of startle amplitude in pulse-alone trials. Another objective of the present study was to evaluate whether habituation to the startling stimulus (i.e., pulse) depends on the initial baseline startle response. RLA rats habituated to the startling stimulus more effectively than RHAs regardless of their baseline startle responses. Conversely, there were no differences in startle habituation in the HS rats grouped by their extreme scores of baseline startle. Altogether, these findings suggest a deficit in information processing in RHA rats, which along with evidence indicating that this strain displays other attentional/cognitive impairments, strengthens the validity of the RHA strain as a putative model of schizophrenia-relevant features.
Topics: Acoustic Stimulation; Animals; Cognition; Habituation, Psychophysiologic; Prepulse Inhibition; Rats; Reflex, Startle; Schizophrenia
PubMed: 35259448
DOI: 10.1016/j.beproc.2022.104618 -
Military Medicine Mar 2023Acute Stress Reactions (ASRs) affect a subgroup of individuals who experience traumatic stress. In the context of military operations, such reactions are often termed...
INTRODUCTION
Acute Stress Reactions (ASRs) affect a subgroup of individuals who experience traumatic stress. In the context of military operations, such reactions are often termed Combat and Operational Stress Reactions (COSRs). COSRs not only encompass all symptoms of ASRs but also include additional symptoms related to military combat and may develop at a rate higher than the general public experiences ASRs. Despite an obvious need, there are currently no approved pharmacologic treatments or guidelines for ASR and/or COSR. Preclinical rodent stress models and behavioral assessments are used to evaluate pharmacotherapies and elucidate underlying mechanisms. Here, we combined established traumatic stress models to develop a model of traumatic stress relevant to military trauma exposure and measured behavioral outcomes that reflect outcomes observed in ASRs and COSRs.
MATERIALS AND METHODS
Adult male rats underwent exposure to either a combination of two or three traumatic stress exposures (e.g., predator exposure, underwater trauma (UWT), and/or inescapable shock) or control procedures. Behavioral performance on the open field, elevated plus maze, and acoustic startle response (SR) was then assessed 24- and 48-hours following stress/control procedures.
RESULTS
In Experiment 1, rats were exposed to a two-stressor model, where predator exposure was coupled with UWT. Minor behavioral deficits were observed in SR for stress-exposed rats as compared to controls. In Experiment 2, inescapable shock was added to predator exposure and UWT. Behavioral performance deficits were observed across all behavioral tests. In Experiment 3, procedures from Experiment 2 were repeated with the only major modification being a shortened predator exposure duration, which resulted in performance deficits in SR only.
CONCLUSIONS
We found that the three-stressor model of Experiment 2 resulted in the greatest overall behavioral disturbance (both in the number of variables and magnitude of stress effects). Interestingly, behavioral deficits elicited from the shorter predator exposure were distinct from those observed with longer predator exposure times. Together, these results generally suggest that combined preclinical stressors with military-relevant elements result in behavioral performance deficits reflective of post-trauma phenotypes in Soldiers. The present findings support the use of both physical and psychological stressors to model operationally relevant traumatic stress exposure.
Topics: Rats; Male; Animals; Humans; Rats, Sprague-Dawley; Military Personnel; Reflex, Startle; Disease Models, Animal; Stress, Psychological; Stress Disorders, Post-Traumatic
PubMed: 35266517
DOI: 10.1093/milmed/usac056 -
Biology Letters Jul 2023Boldness, the way an individual reacts to risk, is a commonly studied personality trait in animals. Consistent among-individual differences in startle response durations...
Boldness, the way an individual reacts to risk, is a commonly studied personality trait in animals. Consistent among-individual differences in startle response durations (latency to recover from a startling stimulus) are frequently assumed to reflect variation in boldness. An alternative explanation is that these latencies are not directly driven by variation in responses to information on risk, but by underlying differences in dynamic performance capacities. Here we investigate this possibility by analysing relationships between locomotory speed, a measure of whole-body dynamic performance capacity in hermit crabs, and startle response duration, a repeatable latency measure used as an index of boldness. Individuals differed in mean startle response duration, in the consistency of their startle responses, in their reaction norms across repeated observations, and mean startle responses increased with crab mass. However, there were no relationships between startle responses and locomotory speed. This indicates that startle responses do not reflect underlying performance capacities and suggests that they provide insight into differences in how individuals respond to risky situations. Since similar latencies are used as measures of boldness in other animals, we suggest that potential relationships between apparent boldness and performance capacity should be tested.
Topics: Animals; Behavior, Animal; Anomura; Reflex, Startle
PubMed: 37490943
DOI: 10.1098/rsbl.2023.0224 -
Psychophysiology May 2024In emergency medical services, paramedics are informed of an emergency call by a high-intensity acoustic alarm called the "call alert." Sudden, loud sounds like the call...
In emergency medical services, paramedics are informed of an emergency call by a high-intensity acoustic alarm called the "call alert." Sudden, loud sounds like the call alert may cause a startle response and be experienced as aversive. Studies have identified an association between the call alert and adverse health effects in first responders; conceivably, these adverse health effects might be reduced by modifying the call alert to blunt its startling and aversive properties. Here, we assessed whether the call alert causes a startle response and whether its startling and aversive properties are reduced when the call alert is preceded by a weak acoustic "prepulse," a process referred to as "prepulse inhibition" (PPI). Paramedics (n = 50; 34M:13F:3 not reported; ages 20-68) were exposed to four call alerts (two with and two without a prepulse) in counterbalanced order. Responses were measured using electromyography (measuring blink amplitude), visual analog scales (quantifying perceived call alert intensity and aversiveness), and an electrocardiogram (assessing heart rate). Paramedics responded to the call alert with a startle reflex blink and an increased heart rate. Acoustic prepulses significantly reduced the amplitude of the call alert-induced startle blink, the perceived sound intensity, and the perceived "dislike" of the call alert. These findings confirm that the call alert is associated with an acoustic startle response in paramedics; adding a prepulse to the call alert can reduce its startling and aversive properties. Conceivably, such reductions might also diminish adverse health effects associated with the call alert in first responders.
Topics: Humans; Prepulse Inhibition; Reflex, Startle; Acoustic Stimulation; Electromyography; Emergency Medical Services
PubMed: 38164815
DOI: 10.1111/psyp.14508 -
Neuroscience and Biobehavioral Reviews Jul 2020Threat conditioning is a laboratory model of associative learning across species that is often used in research on the etiology and treatment of anxiety disorders. At... (Review)
Review
Threat conditioning is a laboratory model of associative learning across species that is often used in research on the etiology and treatment of anxiety disorders. At least 10 different conditioned responses (CR) for quantifying learning in human threat conditioning are found in the literature. In this narrative review, we discuss these CR by considering the following questions: (1) Are the CR indicators of amygdala-dependent threat learning? (2) To what components of formal learning models do the CR relate? (3) How well can threat learning be inferred from the CR? Despite a vast literature, these questions can only be answered for some CR. Among the CR considered, heart period, startle eye-blink and Pavlovian-to-instrumental transfer are most clearly related to amygdala-dependent threat learning. Formal learning models have mostly been studied for skin conductance responses, which are likely to reflect threat prediction and its uncertainty. Startle eye-blink and pupil size appear to best differentiate CS+/CS-, although few direct comparisons between CR exist. We suggest future directions for improving the quantification of threat conditioning.
Topics: Blinking; Cognition; Conditioning, Classical; Fear; Humans; Learning; Reflex, Startle
PubMed: 32343982
DOI: 10.1016/j.neubiorev.2020.04.019 -
Psychophysiology Sep 2019A stimulus (conditioned stimulus, CS) associated with an appetitive unconditioned stimulus (US) acquires positive properties and elicits appetitive conditioned responses...
A stimulus (conditioned stimulus, CS) associated with an appetitive unconditioned stimulus (US) acquires positive properties and elicits appetitive conditioned responses (CR). Such associative learning has been examined extensively in animals with food as the US, and results are used to explain psychopathologies (e.g., substance-related disorders or obesity). Human studies on appetitive conditioning exist, too, but we still know little about generalization processes. Understanding these processes may explain why stimuli not associated with a drug, for instance, can elicit craving. Forty-seven hungry participants underwent an appetitive conditioning protocol during which one of two circles with different diameters (CS+) became associated with an appetitive US (chocolate or salty pretzel, according to participants' preference) but never the other circle (CS-). During generalization, US were delivered twice and the two CS were presented again plus four circles (generalization stimuli, GS) with gradually increasing diameters from CS- to CS+. We found successful appetitive conditioning as reflected in appetitive subjective ratings (positive valence, higher contingency) and physiological responses (startle attenuation and larger skin conductance responses) to CS+ versus CS-, and, importantly, both measures confirmed generalization as indicated by generalization gradients. Small changes in CS-US contingency during generalization may have weakened generalization processes on the physiological level. Considering that appetitive conditioned responses can be generalized to non-US-associated stimuli, a next important step would be to investigate risk factors that mediate overgeneralization.
Topics: Adolescent; Adult; Conditioning, Classical; Female; Food; Generalization, Psychological; Humans; Hunger; Male; Reflex, Startle; Reinforcement, Psychology; Young Adult
PubMed: 31152454
DOI: 10.1111/psyp.13397