Rats showed a substantial increase in locomotor activity when novel objects were introduced into an open-field apparatus. This exploratory locomotion was reduced significantly when glutamic acid diethyl ester HCl, a glutamate antagonist, was injected bilaterally into the nucleus accumbens or when gamma-aminobutyric acid was injected bilaterally into the subpallidal region. These observations provide preliminary support for a contribution of the nucleus accumbens and subpallidal region to exploratory locomotion.