Activity of various CART peptides in changing locomotor activity in the rat.

Several CART (cocaine- and amphetamine-regulated transcript) peptides have been identified in the brain. One peptide, rlCART 55-102, has been previously characterized in locomotor and feeding assays in rodents. The present study characterized the locomotor-stimulating effect of several additional CART peptides after intra-VTA administration in rats. The results confirm earlier findings that intra-VTA administration of rlCART 55-102 dose-dependently increased locomotor activity. Intra-VTA administration of rlCART 62-102 increased activity comparable with that produced by rlCART 55-102. However, intra-VTA administration of rsCART 10-89 and rlCART 55-59 did not increase motor activity. These results suggest that the portion of rlCART 55-102 responsible for increasing motor activity must reside within the portion of the protein also encompassed by rlCART 61-102, as the initial 5-amino acid sequence of rlCART 55-102 did not increase motor activity. In summary, rlCART 55-102 and rlCART 62-102 are behaviorally active in this locomotor assay, while rsCART 10-89 and rlCART 55-59 are not.