logosm.gif (1133 bytes) PANEL OF BEHAVIORAL ASSAYS

ACOUSTIC STARTLE/PREPULSE INHIBITION

This procedure is based on the methods described in: Dulawa SC and Geyer MA. (1996). Psychopharmacology of prepulse inhibition in mice. Chin. J. Physiol. 39(3): 139-146.

Apparatus: Two startle monitor systems (Hamilton-Kinder) consisting of non-restrictive Plexiglas cylinders 5 cm in diameter which are mounted on a platform with a piezoelectric accelometer unit attached below each cylinder, Vibrating standardization unit (San Diego Instruments), digital sound meter (Radio Shack)

Procedure:
1. Bring mice to hallway outside of testing room in home cages.
2. Equilibrate the sensitivities of the two platforms to vibration with a vibrating standardization unit.
3. Calibrate sound pressure levels for background noise and acoustic stimuli with digital sound meter.
4. Place mouse in Plexiglas cylinder, place into startle chamber and allow to habituate to apparatus for 5 minutes with background noise presented continuously.
5. Present five 40-ms broad-band 120 dB bursts with a 15s intertrial interval and record changes in accelometer after each burst (recorded by computer connected to accelometer).
6. Use five different trial types to examine startle versus prepulse inhibition (PPI).

a. a 40-ms broad-band 120 dB burst [STARTLE (pulse alone) trial (p120)]
b. three different PPI trials (prepulse+pulse) trials in which 20-ms long stimuli that are either 4 dB (PPI4), 12 dB (PPI12) or 20 dB (PPI20) above the 65 dB background level precede the 120 dB pulse by 100 ms (onset to onset).
c. NS (no stimulus) contains only background noise and no other acoustic stimuli.
7. The five trial types should be pseudorandomly ordered within each block of five trials in order to control for changes in responsiveness over the test session.
8. Trials should be separated by an average of 15 s.
9. Ten trials of each trial type are presented.
10. Perform two different data transforms to control for differences in startle when comparing the amount of PPI induced across groups.
11. %PPI scores are calculated as the averaged startle magnitude from the STARTLE trials, subtracted by the averaged startle magnitude caused by the PPI trials, all divided by the averaged startle magnitude from the STARTLE trials
12. Another transform should also be employed which uses the same algorithm as the other transform except that %PPI scores are determined for each block of 5 trials across which all trial types are represented. Specifically, a %PPI score is determined each 5-trial block in the session by using values from the STARTLE and PPI trials within each block. This latter transform is used to help control for changes occurring in the magnitude of the response over time.


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