CB1 RECEPTOR LOCALIZATION WITHIN THE AFFERENT SPLANCHNIC NEURONS AND ITS IMPACT ON FEEDING BEHAVIOR AND ENERGY EXPENDITURE

Background: Our previous research has showed that increased sympathetic nervous activity and decreased cannabinoid receptor 1 (CB1) were associated with increased energy expenditure and weight loss following Roux-en-Y gastric bypass (RYGB) in mice. Our study aims to explore the neurological pathways responsible for these effects. Methods: We localized CB1 receptors within the small intestine to specific neuronal cells using immunofluorescence. We administered CB1 receptor agonists anandamide (AEA), and a whole-body inverse agonist rimonabant (Rim), to obese C57Blk/6 mice and measured afferent nerve activity of vagal vs splanchnic fibers. We administered a whole-body vs a peripherally-restricted CB1 antagonist to CB1 sensory neuron-deleted mice vs wild-type controls and measured elements of energy. Results: Immunofluorescence revealed the presence of CB1 receptors in sensory afferent neurons using markers such as calcitonin gene-related peptide (CGRP) and monocyte chemoattractant protein-1 (MCP1) (Fig. 1 A, B). CB1 receptors were highly expressed in the superior mesenteric, celiac ganglion, and nodose ganglion, with a higher abundance observed in the former two (Fig. 1C). Furthermore, using Nav 1.8-tdTomato mice, we observed a greater co-localization of CB1 receptors with Nav 1.8 positive cells in the celiac ganglion and dorsal root ganglion compared to the nodose ganglion (Fig. 1D). This confirmed the localization of CB1 receptors in both splanchnic and vagal sensory neurons, with a higher prevalence in splanchnic neurons. Subsequent measurements of splanchnic and vagal afferent nerves’ activity following local luminal administration of AEA and Rim revealed significant changes in splanchnic nerve activity but not the vagal one (data not shown). We developed a CB1 specific sensory neuron-specific deletion by crossing Nav1.8Cre mice with CB1^flx/flx and we confirmed the model by obtaining CB1 immunofluorescence imaging that showed deletion in vagal and spinal sensory neurons but not in the central nervous system (Fig. 2 A). Mice lacking CB1 receptors exhibited attenuated weight gain and food intake in response to high-fat diet feeding (Fig.2 B). When administered JD5037, a peripherally-restricted CB1 antagonist, these mice had further attenuation of food intake and weight changes experienced on high fat diet (Fig. 2 C, D). Conclusion: Our findings suggest that the endocannabinoid signaling system within afferent splanchnic neurons, play a key role in energy regulation and feeding behavior. This potentially opens the door for further exploration of the pathways involved.