Compulsive behaviors are prominent, disabling, and often treatment-resistant symptoms of several neuropsychiatric disorders, including obsessive compulsive disorder (OCD). Dysfunction within fronto- subcortical brain structures is thought to underlie compulsive behaviors, but the precise circuits involved remain unknown. Currently, chronic (> 4 weeks) treatment with serotonin reuptake inhibitors (SRIs) provides the only effective pharmacological monotherapy for compulsive behaviors; yet, approximately 50% of OCD patients do not respond to SRIs. We have shown that serotonin 1B receptors (5-HT1BRs) regulate the expression of compulsive behaviors. 5-HT1BRs are located on axon terminals of serotonin-containing neurons (presynaptic), and neurons containing other neurotransmitters (postsynaptic)(3), where they inhibit neurotransmitter release when activated. Furthermore, 5-HT1BRs signal through both a canonical G protein- mediated pathway, and a noncanonical G protein-independent pathway. Canonical 5-HT1BR-mediated Gi- signaling requires direct interaction of 5-HT1BRs with glycogen synthase kinase-3 beta (GSK3?). On the other hand, the intracellular scaffolding protein beta arrestin-2 (?-arrestin2) mediates noncanonical 5-HT1BR signaling. We recently found that activation of 5-HT1BRs within the orbitofrontal cortex (OFC) is necessary and sufficient to induce compulsive behaviors in mice. The OFC contains both pre- and postsynaptic 5-HT1BRs, including those on dorsal raphe-OFC and basolateral amygdala (BLA)-OFC projections, respectively. We propose to develop and use a two virus, in vivo CRISPR-Cas9 system to dissect the role of 5-HT1BR density and canonical versus noncanonical signaling within these two circuits in modulating compulsive behaviors.
In Specific Aim 1, we will either overexpress or knockout 5-HT1BR expression within these two projections. We will infuse 1) a Cre recombinase (Cre) dependent adeno-associated virus (AAV) which expresses either 5- HT1BR, or the S. aureus Cas9 (SaCas9) gene plus a guide sequence against 5-HT1BR, into the dorsal raphe or BLA, and 2) a Cre-expressing retrograde canine adenovirus (CAV2-cre) into the OFC.
In Specific Aim 2, we will also use the two virus, in vivo CRISPR-Cas9 system, but will infuse a Cre-dependent AAV expressing SaCas9 and a guide sequence against either ?-arrestin2 or GSK3? into the dorsal raphe or BLA. Mice will be evaluated for 5-HT1BR agonist-induced compulsive behaviors in the open field, a delayed alternation task, and an operant paradigm assessing both acquisition and persistence of habitual lever pressing. The proposed work could establish a novel in vivo CRISPR-Cas9 system for manipulating gene expression within specific neural circuits, and could lead to innovative therapeutic strategies for treating compulsions.

Public Health Relevance

Compulsive behaviors are prominent, disabling, and often treatment-resistant symptoms of several neuropsychiatric disorders. We will develop and use an innovative two virus, in vivo CRISPR- Cas9 system to dissect the role of 5-HT1BR density and canonical versus noncanonical signaling within specific fronto-subcortical circuits in modulating compulsive behaviors. The proposed work could establish a novel in vivo system for manipulating gene expression within specific neural circuits, and could lead to novel therapeutic strategies for treating compulsions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Mental Health (NIMH)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21MH115395-02
Application #
9610717
Study Section
Molecular Neuropharmacology and Signaling Study Section (MNPS)
Program Officer
Winsky, Lois M
Project Start
2017-12-15
Project End
2019-11-30
Budget Start
2018-12-01
Budget End
2019-11-30
Support Year
2
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of California, San Diego
Department
Psychiatry
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093