Fear‐Potentiated Startle and Light‐Enhanced Startle Models in Drug Discovery

Lucianne Groenink1, Elisabeth Y. Bijlsma1, Berend Olivier1

1 Department of Pharmaceutical Sciences, Utrecht Institute for Pharmaceutical Sciences and Rudolf Magnus Institute for Neuroscience, Utrecht University, Utrecht, The Netherlands
Publication Name:  Current Protocols in Pharmacology
Unit Number:  Unit 5.48
DOI:  10.1002/0471141755.ph0548s41
Online Posting Date:  June, 2008
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Described in this unit are the fear‐potentiated startle (FPS) and light‐enhanced startle (LES) tests. These protocols have proven reliable in detecting the anxiolytic properties of test compounds. The principle of these tests is that the magnitude of the acoustic startle reflex is an index of anxiety. The FPS test includes two training sessions in which an intrinsically aversive foot shock is paired with a neutral cue light. In the test session presentation of this cue light is subsequently used to elicit startle potentiation. In the LES test startle reactivity is increased by presentation of bright light. Because LES is based on the innate aversion of rodents for bright light it does not require training sessions. Although LES has been used less frequently than FPS for screening compounds, it has an advantage in that drug effects on startle potentiation are independent of memory retrieval. Further, the contextual anxiety measured in the LES test could be more relevant for pathological anxiety than the conditioned fear associated with the FPS test. Curr. Protoc. Pharmacol. 41:5.48.1‐5.48.15. © 2008 by John Wiley & Sons, Inc.

Keywords: acoustic startle reflex; anxiety; fear conditioning; fear‐potentiated startle; light‐enhanced startle

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Table of Contents

  • Introduction
  • Strategic Planning
  • Basic Protocol 1: Fear‐Potentiated Startle (FPS) in Rats
  • Basic Protocol 2: Light‐Enhanced Startle (LES) in Rats
  • Reagents and Solutions
  • Commentary
  • Literature Cited
  • Figures
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Basic Protocol 1: Fear‐Potentiated Startle (FPS) in Rats

  • Adult male rats (e.g., Wistar), 175 to 225 g on delivery, 10 to 15 rats per dose group
  • Rodent food
  • Test compound solutions (see recipe)
  • Cages for the animals
  • Animal scale
  • Apparatus to measure the acoustic startle response in rats (see Strategic Planning), including programmable shockers and shock grids for each test unit
  • A device for calibrating the test unit (cage calibrators are commercially available from San Diego Instruments, MED Associates, Coulborn Instruments, and TSE systems)
  • Sound level meter (e.g., Bruel and Kjaer, Rion) Data processing system (e.g., Excel, SPSS)

Basic Protocol 2: Light‐Enhanced Startle (LES) in Rats

  • Adult male rats (e.g., Wistar) 175 to 225 g on delivery, group‐housed Test compound solutions (see recipe)
  • Apparatus to measure acoustic startle response in rats (see Strategic Planning), including a fluorescent lamp for bright illumination to elicit light‐enhanced startle (the lamp should not produce heat)
  • Cage calibrator (see protocol 1)
  • Sound level meter (see protocol 1)
  • Light intensity meter (lux meter; e.g., Gossen luxmeter, MAVOLUX, Minolta)
  • Data processing system (e.g., Excel, SPSS)
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Literature Cited

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   Borg, E. 1982. Auditory thresholds in rats of different age and strain. A behavioral and electrophysiological study. Hearing Res. 8: 101‐115.
   Brown, J.S., Kalish, H.I., and Farber, I.E. 1951. Conditioned fear as revealed by magnitude of startle response to an auditory stimulus. J. Exp. Psychol. 41: 317‐327.
   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. 4: 95‐103.
   Davis, M. 1979. Diazepam and flurazepam: Effects on conditioned fear as measured with the potentiated startle paradigm. Psychopharmacology 62: 1‐7.
   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.
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   de Jongh, R., Geyer, M.A., Olivier, B., and Groenink, L. 2005. The effects of sex and neonatal maternal separation on fear‐potentiated and light‐enhanced startle. Behav. Brain Res. 161: 190‐196.
   Grillon, C., Ameli, R., Foot, M., and Davis, M. 1993. Fear‐potentiated startle: Relationship to the level of state/trait anxiety in healthy subjects. Biol. Psychiatry 33: 566‐574.
   Grillon, C., Pellowski, M., Merikangas, K. R., and Davis, M. 1997. Darkness facilitates the acoustic startle reflex in humans. Biol. Psychiatry 42: 453‐460.
   Grillon, C., Baas, J.M.P., Pine, D.S., Lissek, S, Lawley, M., Ellis, V., and Levine, J. 2006. The benzodiazepine alprazolam dissociates contextual fear from cued fear in humans as assessed by fear‐potentiated startle. Biol. Psychiatry 60: 760‐766.
   Hijzen, T.H. and Slangen, J.L. 1989. Effects of midazolam, DMCM and lindane on potentiated startle in the rat. Psychopharmacology 99: 362‐365.
   Hijzen, T.H., Houtzager, S.W., Joordens, R.J., Olivier, B., and Slangen, J.L. 1995. Predictive validity of the potentiated startle response as a behavioral model for anxiolytic drugs. Psychopharmacology 118: 150‐154.
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   Joordens, R.J., Hijzen, T.H., Peeters, B.W., and Olivier, B. 1996. Fear‐potentiated startle response is remarkably similar in two laboratories. Psychopharmacology 126: 104‐109.
   Joordens, R.J., Hijzen, T.H., Peeters, B.W., and Olivier, B. 1997. Control conditions in the fear‐potentiated startle response paradigm. Neuroreport 8: 1031‐1034.
   Josselyn, S.A., Shi, C., Carlezon, W.A. Jr., Neve, R.L., Nestler, E.J., and Davis, M. 2001. Long‐term memory is facilitated by cAMP response element‐binding protein overexpression in the amygdala. J. Neurosci. 21: 2404‐2412.
   Kehne, J.H., Hoffman, D.C., and Cassella, J.V. 1998. Models of schizophrenia: Phencyclidine disruption of prepulse inhibition (PPI) of startle in rats. Curr. Protoc. Pharmacol. 5.15.1‐5.15.12.
   Koch, M. 1999. The neurobiology of startle. Progr. Neurobiol. 59: 107‐128.
   Mansbach, R.S. and Geyer, M.A. 1988. Blockade of potentiated startle responding in rats by 5‐hydroxytryptamine1A receptor ligands. Eur. J. Pharmacol. 156: 375‐383.
   Walker, D.L. and Davis, M. 1997a. Anxiogenic effects of high illumination levels assessed with the acoustic startle response in rats. Biol. Psychiatry 42: 461‐471.
   Walker, D.L. and Davis, M. 1997b. Double dissociation between the involvement of the bed nucleus of the stria terminalis and the central nucleus of the amygdala in startle increases produced by conditioned versus unconditioned fear. J. Neurosci. 17: 9375‐9383.
   Walker, D.L. and Davis, M. 2002a. Light‐enhanced startle: Further pharmacological and behavioral characterization. Psychopharmacology 159: 304‐310.
   Walker, D.L. and Davis, M. 2002b. Quantifying fear potentiated startle using absolute versus proportional increase scoring methods: Implications for the neurocircuitry of fear and anxiety Psychopharmacology 164: 318‐328.
Key References
   Davis et al., 1993. See above.
  Reviews the underlying mechanism of FPS and pharmacological sensitivity.
   Hijzen et al., 1995. See above.
  Thorough investigation into the predictive validity of the FPS test using a wide range of compounds. The importance of adequate control groups is also discussed.
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