Final answer:
An increase in presynaptic dopamine transporters is referred to as 'upregulation.' This biological process adjusts the number of transporters available, typically in response to changes in neurotransmitter levels or the presence of certain drugs.
Step-by-step explanation:
The term that describes an increase in presynaptic dopamine transporters is upregulation. Upregulation refers to the increase in the number of receptors or transporters, such as dopamine transporters, in response to various factors, including changes in neurotransmitter concentrations or drug treatments. This is in contrast to downregulation, which would signify a decrease in the number of receptors or transporters as a means to restore homeostasis when faced with sustained high levels of a neurotransmitter or hormone.