Knowledge in neuropsychobiology continues to benefit from the use of drugs as ‘tools’ to alter neurochemical events as a means of studying interactions between the events and behaviour. Before drugs could play such a role, concepts about basic properties of living organism had to be refined. Techniques had to be invented for investigating the kinetics by which drugs reach their sites of action within the body and the dynamics of their effects once they have occupied their receptors, behaviour being one category of such effects. The present discussion examines these developments in historical perspective, focusing upon influences they have in advancing our understanding of neurochemical substrates of behavi