While it is known that dopamine-2 receptor (D2R) and ghrelin receptor (GHSR1a) signaling in amygdala can relieve the symptoms of stress, there is a fundamental gap to understand how their act at the molecular, cellular and circuit levels to alleviate stress-induced disorders. The long term goal is to understand how the DA-induced stress-response can be modulated by interaction of GHSR1a and D2R for preventive and therapeutic purposes. The overall objective of this proposal is to define the physiological role of DA-signaling dependent on GHSR1a and D2R interaction in amygdala to regulate stress-induced feeding disorder. Our central hypothesis is that by allosterically enhancing DA signaling through GHSR1a:D2R heteromers in the amygdala by treatment with a GHSR1a antagonist the stress response can be regulated in a very specific way. This hypothesis is based on the results of our previously published work showing that D2R-signaling is modulated by allosteric interaction between GHSR1a and D2R. According to structure, GHSR1a antagonist either inhibit or enhance DA signaling in vitro, ex vivo and in vivo by modifying allosteric interaction between GHSR1a and D2R in GHSR1a:D2R heteromers. The rationale for the proposed research is that, fine-tuning DA-signaling in the amygdala by pharmacological targeting GHSR1a:D2R heteromers will lead to new and innovative approaches for preventing and treating stress-related eating disorders. Guided by strong preliminary data, this hypothesis will be tested by pursuing two specific aims: 1) Characterization GHSR1a:D2R heteromer formation in amygdala neurons; and 2) Examine the neuronal circuits dependent on D2R activity in amygdala modulated by GHSR1a:D2R heteromers that control stress-induced feeding behavior. Under the first aim, already proven biophysical and single-molecule approaches will be used to characterize the interactions between GHSR1a and D2R in neurons of amygdala. Under the second aim, to map the neuronal projections of amygdala dependent on GHSR1a the CRE-DOG methodology will be used in Ghsr1a-ires-GFP mice. The Cre- dependent DREADD technology will be used to determine functional connectivity of amygdala in a stress- induced feeding behavior. The proposed research is significant because by exploiting the previously unappreciated mechanism of DA-action through GHSR1a:D2R heteromers we have the opportunity to identify new therapeutic agents that act selectively on neurons coexpressing GHSR1a and D2R, without affecting neurons expressing D2R monomers or homodimers. The proposed research is innovative, because our approach to fine-tune DA transmission by allosteric targeting the protomer partner of D2R in the GHSR1a:D2R heteromeric complex represents a new and substantive departure from traditional strategies for identification of therapeutic agents in CNS. This type of approach is expected to overcome the problems that have been associated with side effects of dopaminergic drugs designed to target D2R in CNS.
The proposed research is relevant to public health because the discovery of the role of GHSR1a:D2R heteromers in the amygdala will provide the basis for new therapeutic avenues designed to treat stress- mediated eating disorders. By targeting GHSR1a:D2R heteromers we have the ability to inhibit or enhance endogenous dopamine signaling through allosteric mechanism and thereby understand how to treat additional stress-induced mental disorders originating in the amygdala. Furthermore, the approach proposed here to regulate D2R signaling in amygdala by GHSR1a:D2R heteromers, is expected to overcome the problems that have been associated with side effects of dopaminergic drugs designed to target D2R in CNS.
