Effects of lesions of the caudate nucleus on morphine dependence in the rat.

Naloxone-precipitated withdrawal and oral self-administration of morphine were compared in norphine-dependent caudate-lesioned and sham animals. The lesion failed to suppress any signs of withdrawal in the dependent-lesioned animals as compared with the shams. However, the dependent-lesioned animals self-administered less morphine that their sham controls. The withdrawal results differed from others previously reported and it was hypothesized that the possibility of development of processes compensatory to the lesion among animals of this experiment, might account for the difference. The results were also discussed in relation to possible dissociation of mechanisms governing physical dependence and self-administration.