Repeated exposure to drugs acting as direct or indirect stimulants of central dopamine transmission results in sensitization to their behavioural stimulant properties (behavioural sensitization). Priming provides a simple model of behavioural sensitization particularly suitable for studies of its neural and molecular mechanisms. The results obtained to date indicate that priming results in an increased responsiveness of postsynaptic dopamine receptor mechanisms in the caudate nucleus, possibly due to an increased affinity of the D-1 receptor for its agonist.