This Article Full Text (OnlineFirst PDF) All Versions of this Article: 0269881107083843v1 22/8/828    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Al-Abduljawad, K. Articles by Szabadi, E. Search for Related Content PubMed PubMed Citation Articles by Al-Abduljawad, K. Articles by Szabadi, E. Social Bookmarking                         What's this?

Effects of threat of electric shockand diazepam on the N1/P2auditory-evoked potential elicited by low-intensity auditory stimuli

¹ Department of Audiology, College of Applied Medical Sciences, King Saud University,Riyadh 11656, Saudi Arabia.
² Psychopharmacology Section, Division of Psychiatry, University of Nottingham, Nottingham, UK

^* To whom correspondence should be addressed.

	Abstract

The acoustic startle response includes rapid muscular contractionselicited by loud sounds; it may be measured in humans as the electromyographicresponse of the orbicularis oculi muscle. Enhancementof this response during exposure to threat of electric shock (fearpotentiatedstartle) is a widely used model of human anxiety. A problemwith the use of the startle reflex in studies of human anxiety is theaversiveness of startle-eliciting sounds, which may, in some subjects,exceed the aversiveness of the electric shock itself. We have recentlyfound that the long-latency N1/P2 auditory-evoked potential elicited byloud sounds is subject to fear potentiation. However, it is not knownwhether N1/P2 potentials elicited by low-intensity sounds, which do notelicit the startle response, are also subject to fear potentiation. Thisstudy examined the susceptibility of the N1/P2 potential elicited by lowintensitysounds to fear potentiation, and the effect of the anxiolyticdiazepam on the N1/P2 potential in the absence and presence of threatof electric shock. Fifteen male volunteers (18-43 years) participated inthree sessions in which they received placebo, diazepam 5mg anddiazepam 10mg according to a double-blind protocol. Sixty minutes aftertreatment, auditory-evoked potentials were elicited by 40ms 1 kHz tones5, 10, 15, 20 and 25 dB[A] above a background of 70 dB[A]. Recordingsessions consisted of eight alternating 2 min THREAT and SAFE blocks;unpredictable shocks (1.8 mA, 50ms) were delivered to the subject'swrist in THREAT blocks (1-4 shocks per block). The amplitude of theN1/P2 potential increased monotonically as a function of stimulus intensity.The responses were significantly greater during THREAT blocks thanduring SAFE blocks (fear potentiation). Diazepam attenuated theresponses in both the SAFE and THREAT conditions. Fear potentiation ofthe N1/P2 potential was significantly reduced by diazepam. Diazepamreduced subjective alertness and lowered critical flicker fusion frequency,a measure of arousal. The results suggest that fear potentiation of theN1/P2 potential is not simply a manifestation of the fear-potentiatedstartle response. The use of low-intensity stimuli may be advantageous instudies of fear potentiation in humans.

Key Words: N1/P2 auditory-evoked potential, diazepam, fear potentiation, humans

First published on January 21, 2008, doi:10.1177/0269881107083843

Journal of Psychopharmacology 2008;22:828.

A more recent version of this article appeared on November 1, 2008


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?