Terminal type-specific cannabinoid CB1 receptor alterations in schizophrenia and cannabis use - PROJECT SUMMARY/ABSTRACT Individuals with schizophrenia (SZ) use cannabis at a high rate, which exacerbates SZ symptoms and worsens long-term prognosis. Recent studies suggest that while individuals with genetic risks for SZ are more likely to use cannabis, cannabis users are also at a dually (i.e., genetically and pharmacologically) increased risk for the expression of SZ related symptoms. The psychoactive substance in cannabis, Δ9-tetrahydrocannabinol (THC), targets the G-protein coupled receptor (GPCR) cannabinoid CB1 receptor (CB1R) in the brain. I recently showed that CB1R is expressed in both excitatory and inhibitory axon terminals in the human dorsolateral prefrontal cortex (DLPFC) – a region implicated in working memory impairments of SZ. Then, I found increased CB1R in excitatory terminals, and decreased CB1R in inhibitory terminals, in the DLPFC of SZ subjects without comorbid cannabis use. Conversely, in a pilot analysis of THC-exposed rats, I saw decreased CB1R in inhibitory terminals in the prelimbic cortex (PrL) – a functional homolog of the DLPFC – but no changes in excitatory terminals. I now propose to expand on these results to characterize the independent and additive effects of SZ and cannabis use on terminal type-specific CB1R expression and signaling, and resulting functional alterations. I hypothesize that individuals with SZ have terminal type-specific CB1R aberrations that contribute to impaired working memory. THC exposure then intensifies these terminal type-specific CB1R changes, further worsening working memory. I will test this hypothesis using the synergistic strengths of cross-species analyses, through a set of postmortem and rat experimental Aims, to clarify the effects of findings observed in human samples with preclinical studies. Multi-label immunohistochemistry and confocal microscopy will be used to define the terminal type-specific CB1R alterations in the DLPFC of SZ individuals with and without comorbid cannabis use (Aim 1). Viral manipulations and intravenous rat THC self-administration, followed by working memory tests, will be used to delineate how terminal type-specific CB1R changes and THC exposure alter working memory (Aim 2). Proximity labeling and targeted mass spectrometry will be used to compare terminal type-specific CB1R phosphopeptide alterations in the DLPFC of SZ individuals with and without comorbid cannabis use, and the PrL of rats with and without THC exposure (Aim 3). Integrated with the scientific Aims is training to 1) Develop expertise in translational studies of SZ cortical cell and circuit pathology. 2) Acquire expertise in the design and execution of in vivo viral mediated gene transfer. 3) Train in the design and execution of THC self-administration. 4) Enhance knowledge of GPCR signaling biology using phosphoproteomics. 5) Learn advanced biostatistics to analyze complex postmortem and rodent datasets. Achieving these Aims will identify the independent and additive effects of SZ and cannabis use on terminal type-specific CB1R expression and signaling in the DLPFC, and the resulting functional alterations. The training and knowledge gained will support future R01 testing strategies to rescue CB1R abnormalities, and provide me with the necessary skills to establish a successful independent, NIH-funded research program.
