Fear‐Potentiated Startle in Rats

Michael Davis1

1 Emory University School of Medicine, Atlanta, Georgia
Publication Name:  Current Protocols in Neuroscience
Unit Number:  Unit 8.11A
DOI:  10.1002/0471142301.ns0811as14
Online Posting Date:  May, 2001
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Fear‐potentiated startle measures the increase in the startle reflex elicited by a sudden noise in the presence of a cue that has previously been paired with footshock. It involves an initial training session in which a cue, such as a light, is paired with footshock, and then a later test session in which startle is elicited in the presence or absence of the cue. It thus involves associative learning, memory for that association measured during the retention test, and conditioned fear in the presence of the cue. Drugs that interfere with learning, memory, or fear and anxiety can alter fear‐potentiated startle depending on when they are given with respect to training and testing.

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Table of Contents

  • Commentary
  • Literature Cited
  • Figures
  • Tables
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Basic Protocol 1:

  • 300‐ to 400‐g rats (strains of rats include Sprague‐Dawley, Long‐Evans, and Wistar; both males and females over a wide range of ages and animal weights)
  • Startle test cage that puts out a voltage proportionate to the magnitude of the startle response (e.g., Coulbourn Instruments; MED Associates; San Diego Instruments) or built according to the specifications described in Cassella and Davis ( ), see Figure
  • Macintosh computer with software written and distributed by Eric Harris‐Braun (61 Pond Brook Road, Newtown, Conn. 06470, 203‐426‐8999, ) (e.g., MAC‐OS 8.0 or higher in conjunction with a 200 PCI InstruNET controller board and a 100‐B InstruNET device, GW Instruments). Although this software currently has drivers that support InstruNET hardware, drivers for other hardware including the commercially available hardware listed above can be added by Eric Harris‐Braun. This software allows one to easily program the computer to turn on and off tones, lights, shocks, or startle stimuli at various intervals and times. The software samples the output of the startle cage after presentation of the startle stimulus, converts this to a number and sorts the data as a function of the type of test trial given.
  • Sound‐attenuated housing for test cages (e.g., Industrial Acoustics)
  • Sample and hold circuit to sample cage output for brief period of time after onset of startle‐eliciting stimulus (e.g., 200 PCI InstruNET controller board and a 100‐B InstruNET device; GW Instruments)
  • Analogue‐to‐digital converter to convert voltage to a number (e.g., 200 PCI InstruNET controller board and a 100‐B InstruNET device, GW Instruments)
  • Noise generator to provide constant level of background white noise (e.g., 60 dB; ACO Pacific)
  • Noise generator to provide startle stimulus (ACO Pacific)
  • Stereo power 250‐W amplifier to amplify startle stimulus as well as background noise (e.g., Radio Shack)
  • 90‐ to 20,000‐Hz wide band 5‐in. midrange speaker for background noise (e.g., Radio Shack)
  • 5‐ to 40‐kHz high frequency tweeter for startle stimulus (e.g., Radio Shack Supertweeters)
  • Relay equipment that can be driven by computer to gate input from noise generator to amplifier to allow delivery of a startle stimulus for 50 msec. Alternatively, it is possible to use the sound system of the computer to generate “sound files” of the appropriate duration, frequency, etc. The audio output of the computer is then fed to the power amplifier and out to the speaker. The software can be programmed to “call up” these sound files to produce startle stimuli or auditory conditioned stimuli.
  • Method to vary startle stimulus intensity from trial to trial. This can involve sets of relays and attenuators or can be controlled digitally from computer‐driven systems using commercially available equipment or the Harris‐Braun software.
  • Light source for conditioned stimulus (DC bulb that can be turned on by a relay connected to a DC power supply or AC bulb that can be turned on by a relay that can switch 110 V)
  • Shock generator and scrambler that can be operated by relay (BRS LVE), see for a discussion of issues pertaining to calibration and measurement of shock intensity
  • Medium sandpaper
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Literature Cited

   Brown, J.S., Kalish, H.I., and Farber, I.E. 1951. Conditional fear as revealed by magnitude of startle response to an auditory stimulus. J. Exp. Psychol. 41:317‐328.
   Campeau, S. and Davis, M. 1992. Fear potentiation of the acoustic startle reflex using noises of various spectral frequencies as conditioned stimuli. Anim. Learn. Behav. 20:177‐186.
   Cassella, J.V. and Davis, M. 1986. The design and calibration of a startle measurement system. Physiol. Behav. 36:377‐383.
   Davis, M. 1993. Pharmacological analysis of fear‐potentiated startle. Braz. J. Med. Biol. Res. 26:235‐260.
   Davis, M. and Astrachan, D.I. 1978. Conditioned fear and startle magnitude: Effects of different footshock or backshock intensities used in training. J. Exp. Psychol.: Anim. Behav. Proc. 4:95‐103.
   Davis, M., Schlesinger, L.S., and Sorenson, C.A. 1989. Temporal specificity of fear‐conditioning: Effects of different conditioned stimulus‐unconditioned stimulus intervals on the fear‐potentiated startle effect. J. Exp. Psychol.: Anim. Behav. Proc. 15:295‐310.
   Davis, M., Falls, W.A., Campeau, S., and Kim, M. 1993. Fear‐potentiated startle: A neural and pharmacological analysis. Behav. Brain Res. 58:175‐198.
   Falls, W.A. and Davis, M. 1994. Fear‐potentiated startle using three conditioned stimulus modalities. Anim. Learn. Behav. 22:379‐383.
   Walker, D.L., Cassella, J.V., Lee, Y., de Lima, T.C.M., and Davis, M. 1997. Opposing roles of the amygdala and dorsolateral periaqueductal gray in fear‐potentiated startle. Brain Res. Bull. 111:692‐702.
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