Abstract The influence of a direct change in the biogenic amines of the central nervous system on the stimulation threshold of rats for a particular behavioural response, motor hyperactivity, was investigated. Norepinephrine, 5-hydroxytryptamine and dopamine were administered intrahypothalamically. An increase in stimulation threshold was clearly observed only after benzoquinolizine, injected intraperitoneally. Other substances caused little or no change in the stimulation threshold. There were no specific influences of norepinephrine, 5-hydroxytryptamine and dopamine on the stimulation threshold in these experiments.