Ghrelin receptor antagonism of hyperlocomotion in cocaine-sensitized mice requires [beta]arrestin-2

• Published in: Synapse (New York, N.Y.) Vol. 72; no. 1
• Main Authors: Toth, Krisztian, Slosky, Lauren M, Pack, Thomas F, Urs, Nikhil M, Boone, Peter, Mao, Lan, Abraham, Dennis, Caron, Marc G, Barak, Lawrence S
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.01.2018
• Subjects: Actin; Addictions; Addictive behaviors; Arrestin; Behavioral plasticity; Cocaine; Feeding behavior; Ghrelin; Growth hormones; Reinforcement; Rodents; Synaptic plasticity
• ISSN: 0887-4476; 1098-2396
• DOI: 10.1002/syn.22012

The "brain-gut" peptide ghrelin, which mediates food-seeking behaviors, is recognized as a very strong endogenous modulator of dopamine (DA) signaling. Ghrelin binds the G protein-coupled receptor GHSR1a, and administration of ghrelin increases the rewarding properties of psychostimulants while ghrelin receptor antagonists decrease them. In addition, the GHSR1a signals through [beta]arrestin-2 to regulate actin/stress fiber rearrangement, suggesting [beta]arrestin-2 participation in the regulation of actin-mediated synaptic plasticity for addictive substances like cocaine. The effects of ghrelin receptor ligands on reward strongly suggest that modulation of ghrelin signaling could provide an effective strategy to ameliorate undesirable behaviors arising from addiction. To investigate this possibility, we tested the effects of ghrelin receptor antagonism in a cocaine behavioral sensitization paradigm using DA neuron-specific [beta]arrestin-2 KO mice. Our results show that these mice sensitize to cocaine as well as wild-type littermates. The [beta]arrestin-2 KO mice, however, no longer respond to the locomotor attenuating effects of the GHSR1a antagonist YIL781. The data presented here suggest that the separate stages of addictive behavior differ in their requirements for [beta]arrestin-2 and show that pharmacological inhibition of [beta]arrestin-2 function through GHSR1a antagonism is not equivalent to the loss of [beta]arrestin-2 function achieved by genetic ablation. These data support targeting GHSR1a signaling in addiction therapy but indicate that using signaling biased compounds that modulate [beta]arrestin-2 activity differentially from G protein activity may be required.