Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Indeed, peripherally injected BC264 induced a hyperlocomotor activity in rats by increasing the extracellular levels of dopamine (Ladurelle et al. 1997) and of Met-enkephalin-like immunoreactivity in the anterior nucleus accumbens.
Category: