tokens: Male Wistar rats were implanted bilaterally with cannulae into the accumbens shell or core , and then were locally injected with GR 55562 ( an antagonist of 5 - HT1B receptors ) or CP 93129 ( an agonist of 5 - HT1B receptors ). Given alone to any accumbal subregion , GR 55562 ( 0 .