Ja. Mccaughran et al., Fear-potentiated startle response in mice: Genetic analysis of the C57BL/6J and DBA/2J intercross, PHARM BIO B, 65(2), 2000, pp. 301-312
The role of genetic factors in the fear-potentiated startle (FPS) response
was examined in the inbred C57BL/6J (B6) and DBA/2J (D2) mouse strains. Mic
e in the D2 strain displayed a significant potentiation in the acoustic sta
rtle response (ASR) when presented with a visual condition stimulus (CS) pr
eviously paired with an aversive unconditioned stimulus (US). The maximal F
PS response was observed following 20 conditioning trials but a near maxima
l response was noted following as few as five trials. Forty conditioning tr
ials produced a significant reduction in the FPS response that may be relat
ed to overtraining. The FPS response in the B6 strain was significantly low
er than the D2 strain, regardless of the number of conditioning trials. The
contrasting FPS responses were not related to differences in auditory sens
itivity known to exist between these strains. Analysis of a full Mendelian
cross formed from the B6 and D2 strains found that the FPS response was a h
ighly heritable trait, best described by a simple additive model of inherit
ance and with a broad-sense heritability of 0.46. The distribution of the F
PS response in F2 hybrids formed from the intercross of the D2 and B6 strai
ns was continuous which suggests a multigenic substrate. The light + noise
and noise-alone trial types were highly correlated, but no association was
detected between the baseline ASR amplitude and the FPS response. Mice from
the phenotypic extremes of the F2 distribution displayed FPS responses tha
t were more extreme than either of the progenitor strains. However, both ba
seline startle amplitude and the salience of auditory stimuli did not diffe
r in these groups. The results of this study confirm an early report by Fal
ls et al. (1997), and provide additional quantitative genetics information
necessary for the eventual mapping of the chromosomal regions or genes asso
ciated with the FPS response in mice. (C) 2000 Elsevier Science Inc.