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PubMedDate not supplied

Multiple serotonin receptor subtypes modulate prepulse inhibition of the startle response in rats.

The phenomenon of prepulse inhibition (PPI) of the acoustic startle reflex is widely used as an operational measure of sensorimotor gating mechanisms. Because sensorimotor gating abnormalities have been identified in schizophrenic patients, the exploration of the neural substrates involved in PPI may provide insight into the neural dysfunctions underlying this disorder. Both dopaminergic and glutamatergic systems are involved in the modulation of PPI in rats. In addition, the present studies demonstrate complex serotonergic influences in this phenomenon. Specifically, both the 5-HT2 agonist, DOI, (2,5-dimethoxy-4-iodoamphetamine), and the 5-HT1B agonist, RU 24969, [5-methoxy-3(1,2,3,6)tetrahydropyridin-4- yl]-1H-indole, potently and reversibly disrupted PPI. The 5-HT2C agonist mCPP, [1-(m)-chlorophenyl-piperazine], was ineffective. Furthermore, ketanserin (2.0 mg/kg) and haloperidol (0.1 mg/kg) but not (+/-)propranolol (20.0 mg/kg) blocked the effect of DOI. In addition, the same doses of haloperidol, and, to a lesser extent, (+/-)propranolol, prevented the disruption of PPI induced by RU 24969. Together with previous reports of 5-HT1A involvement in PPI, these results argue for multiple serotonergic mechanisms in the modulation of PPI.

Acoustic Stimulation↗
PubMed1984

Diethyldithiocarbamate depresses the acoustic startle response in rats.

The relationship between norepinephrine (NE) content in cortex and spinal cord and acoustic startle amplitude was investigated in two experiments. Administration of diethyldithiocarbamate (DDC) depressed startle amplitude at the same time and dose that it most severely depleted NE content. These results support the conclusion that NE facilitates the normal elaboration of the acoustic startle reflex and also support evidence that NE activity in the spinal cord may be of particular importance in the maintenance of normal startle amplitude.

Acoustic Stimulation↗
PubMed1997

Anxiogenic effects of high illumination levels assessed with the acoustic startle response in rats.

Previous studies have shown that the amplitude of the acoustic startle reflex is increased by the presentation of aversive stimuli. In the present study, the amplitude of acoustic startle in rats was increased by exposure to high illumination levels. The effect was directly related to the intensity (0, 8, 70, and 700 footlamberts) of illumination (experiment I); was blocked by the anxiolytic compound buspirone (experiment II); and showed little or no habituation with repeated testing (experiment III). These results suggest that the elevation of startle amplitude by light may reflect an unconditioned anxiogenic effect of high illumination levels. The possible utility of this phenomenon as an animal model of anxiety is discussed.

Acoustic Stimulation↗
PubMed2002

Affective imagery and the startle response: probing mechanisms of modulation during pleasant scenes, personal experiences, and discrete negative emotions.

Two experiments addressed the following issues concerning modulation of the acoustic startle reflex during emotional imagery: (1) Is startle inhibited or potentiated during imagery of pleasurable events? (2) Does startle modulation differ for personal versus standard imagery scenes? (3) Is startle modulated differently during anger versus fear? For standard scenes, startle was greater during aversive than pleasant imagery, with both exceeding neutral. Blink potentiation was greater during imagery of personal pleasant than nonpersonal pleasant scenes. Startle potentiation did not differ for anger versus fear material, but differences were found in self-report, corrugator EMG, and HR response. These results suggest that in addition to the emotional valence of imagined material, startle reactivity is influenced by the degree of engagement or active disengagement from the sensory environment. The findings also indicate that fear and anger are differentiable in terms of affective report, cardiac mobilization, and expressive behavior, but not at the primary motivational level at which reflex priming occurs.

Adolescent↗
PubMed1995

Modification of the acoustic startle response in hearing-impaired C57BL/6J mice: prepulse augmentation and prolongation of prepulse inhibition.

Modification of acoustic startle amplitude by a 10-ms tone prepulse (S1) was evaluated as a function of the interstimulus interval (ISI) between the onset of S1 and the onset of the startle-evoking stimulus (S2). Subjects were normal-hearing 1-month-old C57BL/6J (C57) mice and CBA/CaJ mice and 5-month-old C57 mice with high-frequency hearing loss. With a 2-ms ISI, 5-month-old C57 mice (but not the normal-hearing mice) exhibited pronounced prepulse augmentation (PPA) of startle: Amplitudes were much larger when S1 was present. Prepulse inhibition (PPI) occurred with ISIs of 10-100 ms in all subject groups. With long ISIs of 200 and 500 ms, however, PPI was strong only in 5-month-old C57 mice and only with S1 frequencies of 8, 12, and 16 kHz. Physiological studies of neural plasticity have shown that frequencies of 8-16 kHz become "over-represented" (more neurons responding) in the central auditory system of C57 mice, suggesting a link with prolonged PPI observed here.

Animals↗
PubMedDate not supplied

Effects of lysergic acid diethylamide (LSD) on temporal recovery (pre-pulse inhibition) of the acoustic startle response in the rat.

In a series of 6 experiments 40 mug/kg d-lysergic acid diethylamide (LSD) augmented acoustic startle amplitude in rats when long intertone intervals (4, 8, 16, or 32 sec) were used but not when short interstimulus intervals were used (0.02, 0.1, 0.5, 1, or 2 sec). In contrast, 8 mg/kg d-amphetamine augmented startle when either long or short interstimulus intervals were used. The results suggest that LSD augments startle by accelerating the decay of pre-pulse inhibition (temporal recovery process) which may be one mechanism by which LSD can alter sensory processing.

Acoustic Stimulation↗
PubMed2004

The Impact of Event Scale--Revised: evaluation of the subscales and correlations to psychophysiological startle response patterns in survivors of a life-threatening cardiac event: an analysis of 129 patients with an implanted cardioverter defibrillator.

BACKGROUND: The aim of the present study was to examine the reliability and validity of the Impact of Event Scale-Revised (IES-R) with special emphasis on the evaluation of the hyperarousal subscale against a standardized psychophysiological measurement. METHODS: A total of 129 survivors of a life-threatening cardiac event underwent a psychodiagnostic evaluation and a psychophysiological acoustic startle reflex (ASR) paradigm. The ASR assessed the magnitude and habituation of electromyogram (EMG) and skin conductance responses (SCR) in response to the delivery of 15 acoustic startle trials. Pearson correlation and factor analysis was used to measure reliability and construct validity. The hyperarousal subscale was validated against the ASR in terms of sensitivity and specificity mainly using receiver operating characteristic (ROC) curve analysis. RESULTS: A high reliability was found for the intrusion and avoidance subscale (alpha>0.8); however, the hyperarousal subscale showed a weaker reliability (alpha=0.66). No avoidance item, one intrusion item but four hyperarousal items revealed higher correlations to another than its assigned subscale. The hyperarousal subscale was not able to discriminate sufficiently between patients with and without exaggerated startle reactions as indicated by ROC curves running near the diagonal line. LIMITATIONS: The scores in all three subscales are lower compared to subjects traumatized by non-cardiac events. CONCLUSIONS: Reliability and construct validity for the intrusion and avoidance subscale proved to be high but was only sufficient for the hyperarousal subscale. Moreover, the criterion validity of the hyperarousal subscale regarding psychophysiological measurements is arguable and indicates further investigations in this area.

Acoustic Stimulation↗
PubMed1975

Effects of d- and l-amphetamine on habituation and sensitization of the acoustic startle response in rats.

In a series of 3 experiments the effects of 2, 4, 8, or 16 mg/kg d-amphetamine and 4, 8, 16, or 32 mg/kg l-amphetamine on acoustic startle amplitude in the rat were investigated. d-Amphetamine was 4--5 times as potent as l-amphetamine in augmenting startle amplitude. Startle potentiation was associated with vigorous stereotypies but the resultant cage movement could not account for the change in startle. Pretreatment with alpha-methyl-p-tyrosine (100 mg/kg, 1 hr before) had only a slight depressant effect on startle but essentially eliminated augmentation of startle by either d-amphetamine (8 mg/kg) or l-amphetamine (32 mg/kg). d-Amphetamine did not have a direct effect on startle but instead enhanced sensitization produced by the startle stimuli without altering sensitization produced by background white noise or habituation. The results suggest that startle sensitization is enhanced by increased availability of catecholamines and, by virtue of the different potencies of the d- and l-isomers, that dopamine and norepinephrine may affect startle differently.

Acoustic Stimulation↗
PubMed1979

Development of the acoustic startle response in the rat: ontogenetic changes in the magnitude of inhibition by prepulse stimulation.

Three experiments examined the development of the acoustic startle reflex and its modification by a preliminary stimulus in the infant rat during the 2nd and 3rd postnatal weeks. The 1st experiment employed a white noise S1 (20 msec, 70 dB), the 2nd a cutaneous S1 (.5 msec, .5 mA and 1.0 mA shock), and the 3rd identical S1-S2 pairs (20 msec, 10 kHz, 110 dB tones). The results demonstrate a similar maturation of the prepulse modification pattern over days in the 3 experiments, evidenced mainly in the growth of inhibition. The findings indicate peripheral and central mechanisms that are maturing during the period of life under observation and that contribute to the developmental patterns of modification.

Acoustic Stimulation↗
PubMed1999

Smoking cues decrease prepulse inhibition of the startle response and increase subjective craving in humans.

The present study investigated whether exposure to smoking cues would attenuate prepulse inhibition (PPI) of the startle reflex and increase craving among smokers across 2 experimental sessions. It was hypothesized that exposure to smoking cues would result in a decrease in PPI. Twenty-six smokers were exposed to smoking cues and control cues in 2 experimental sessions 1 week apart. Results indicate that smoking cues reliably attenuated PPI in both the 1st and 2nd sessions as compared with control cues. Findings also suggest that smoking cues reliably increased craving, increased negative affect, and reduced positive affect relative to baseline measures in both sessions. Results are consistent with the premise that exposure to smoking cues precipitates increases in dopamine activation or changes in information processing that cause a disruption of PPI.

Adolescent↗
PubMed1986

Differential effects of dopamine agonists on acoustically and electrically elicited startle responses: comparison to effects of strychnine.

This study sought to determine where drugs that are known to alter sensorimotor reactivity measured with the acoustic startle reflex ultimately act within the acoustic startle pathway. To do this, startle was elicited either acoustically or electrically within various nuclei believed to comprise the acoustic startle pathway. Direct infusion of serotonin into the subarachnoid space of the lumbar spinal cord increased acoustic startle and startle elicited electrically through the ventral cochlear nucleus (VCN) to a comparable degree. Subconvulsant doses of strychnine increased startle elicited acoustically or electrically through either the VCN or the nucleus reticularis pontis caudalis (RPC), pointing to a spinal locus of action of strychnine after systemic administration. In marked contrast, the dopamine agonists d-amphetamine and apomorphine consistently increased acoustic startle but actually depressed startle elicited electrically through the VCN or the RPC. These later results suggest that dopamine agonists increase sensorimotor reactivity measured with acoustic startle by acting on sensory rather than motor parts of the reflex arc.

Acoustic Stimulation↗
PubMed2004

Rejection sensitivity and the defensive motivational system: insights from the startle response to rejection cues.

Rejection sensitivity (RS) is the disposition to anxiously expect, readily perceive, and intensely react to rejection. This study used the startle probe paradigm to test whether the affect-based defensive motivational system is automatically activated by rejection cues in people who are high in RS. Stimuli were representational paintings depicting rejection (by Hopper) and acceptance (by Renoir), as well as nonrepresentational paintings of either negative or positive valence (by Rothko and Miro, respectively). Eyeblink startle magnitude was potentiated in people high in RS when they viewed rejection themes, compared with when they viewed nonrepresentational negative themes. Startle magnitude was not attenuated during viewing of acceptance themes in comparison with nonrepresentational positive themes. Overall, the results provide evidence that for people high in RS, rejection cues automatically activate the defensive motivational system, but acceptance cues do not automatically activate the appetitive motivational system.

Adolescent↗
PubMed1995

Startle responses of spider phobics to masked stimuli: a pilot study.

The present study tested the hypothesis that briefly flashed and backwardly masked phobic stimuli potentiate startle reflexes in phobic subjects. Spider phobic (n = 17) and normal control (n = 12) subjects were exposed to short (30 ms) and backwardly masked presentations of phobic slides (i.e., spiders) and neutral slides (i.e., flowers, mushrooms, snakes). On half the trials, eyeblink startle reflexes were elicited with auditory probes following presentation of the slides. In spite of the degraded stimulus conditions, there were some indications that phobics exhibited a startle pattern different from control subjects. More specifically, phobic subjects tended to react with larger startles during the second block of spider trials than control subjects. No such group differences were found for the neutral trials. As the eyeblink startle reflex is closely linked to the thalamo-amygdala pathway, the present findings provide some preliminary support for the idea that the preattentive processing of phobic cues is located at the subcortical level.

Adult↗