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:Astrocyte swelling also depletes organic osmolytes, such as taurine, which has GABAA receptor agonistic effects (Chepkova et al., 2002) and whose uptake is involved in the long-lasting enhancement of synaptic transmission and may therefore affect synaptic plasticity (Sergeeva et al., 2003).
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