Pretreatment of rats for 4 days with the selective dopamine D, recepto
r agonist A-77636 attenuated the ability of cocaine to induce locomoto
r hyperactivity and to stimulate the expression of the proto-oncogene
c-fos in the striatum and nucleus accumbens. Our results suggest that
repeated D-1 agonist treatment leads to subsensitivity of D-1 receptor
s involved in mediating some of the effects of cocaine on behavior and
gene expression.