Dopamine D4 receptor (D4R) deletion in mice does not affect operant responding for food or cocaine.

In this study we examined the genetic contribution of the D4R in food and cocaine self-administration using D4R mice. Mice were examined for operant responding to food pellets or intravenous cocaine. Compared to wild-type mice (D4R(+/+)), both heterozygous (D4R(+/-)) and knockout (D4R(-/-)) mice showed no difference in responding for food or cocaine.