tokens: The later enhancement was attenuated after intra - accumbens shell treatment with GR 55562 ( 1 microg / side ). Our findings indicate that cocaine induced hyperlocomotion is modified by 5 - HT1B receptor ligands microinjected into the accumbens shell , but not core , this modification consisting in inhibitory and facilitatory effects of the 5 - HT1B receptor antagonist ( GR 55562 ) and agonist ( CP 93129