Table 2.

Effects of amphetamine on the acoustic startle response for D2R, D3R, and D4R mutant mice

	Wild-type (+/+)	Heterozygote (+/−)	Knock-out (−/−)
D2R Male
Vehicle	211.4  ± 34.0	273.4  ± 30.8	252.4  ± 47.2
AMPH	102.2  ± 23.6*	217.6  ± 26.4*	176.6  ± 26.4*
D2R Female
Vehicle	191.6  ± 45.6	202.8  ± 40.0	159.2  ± 27.8
AMPH	90.8  ± 20.4**	152.6  ± 27.8**	102.0  ± 21.0**
D3R Male
Vehicle	138.2  ± 62.6	—	244.5  ± 78.2
AMPH	59.1  ± 21.9**	—	67.9  ± 20.8**
D4R Male
Vehicle	349.2  ± 47.2	—	234.6  ± 55.6
AMPH	75.4  ± 15.2**	—	69.0  ± 9.6**
D4R Female
Vehicle	321.0  ± 56.6	—	256.4  ± 38.6
AMPH	91.6  ± 22.2**	—	108.6  ± 30.6**

Amphetamine (10.0 mg/kg, 5 ml/kg volume) significantly reduced the acoustic startle response for D2R, D3R, and D4R mutant mice. Values (arbitrary units) represent mean ± SEM startle magnitude.

*p < 0.05; **p < 0.01 versus vehicle control (0.9% saline).