tokens: In the present study , we investigated the changes occurring at the protein level in striatal samples obtained from the unilaterally 6-hydroxydopamine - lesion rat model of PD treated with saline , L-DOPA or bromocriptine using two - dimensional difference gel electrophoresis and mass spectrometry ( MS ). Rats treated with L-DOPA were allocated to two groups based on the presence or absence of LID .