Chloe E Johnson
Florida State University
Co-authors: Douglas A. Storace1, Adam K. Dewan1
1Florida State University
The endocannabinoid system is a widespread neuromodulatory network that influences numerous aspects of sensory perception including olfactory processes. Previous research in rodents has suggested that endocannabinoids may regulate food intake through an olfactory-dependent mechanism (Soria-Gómez & Bellocchio et al. 2014). Specifically, cannabinoid type-1 (CB1) receptors within the granule cell layer of the main olfactory bulb (MOB) were proposed to stimulate ingestion in fasted mice by enhancing their olfactory sensitivity.
To further explore this phenomenon, we used an operant conditioning go/ no-go assay with highly reproducible odor stimulus delivery to measure olfactory thresholds in mice. Infusions of the CB1 agonist, WIN 55,212-2, (WIN) directly into the granule cell layer (GCL) of the MOB in these animals, yielded a significant decrease in behavioral sensitivity as compared to vehicle or no manipulation (p = 0.001). Intrabulb infusions of the CB1 antagonist, AM251, into the GCL did not have a significant effect on olfactory sensitivity compared to vehicle (p = 0.35).
Further, peripheral injections of WIN also did not influence odor detection (p = 0.76), contrary to previous findings utilizing this manipulation. These results indicate that exogenous cannabinoids acting on granule cells, blunt rather than enhance olfactory sensitivity, at least in non-fasted mice. Additional research is needed to uncover how metabolic state (e.g., fasting) influences cannabinoid signaling within the olfactory bulb and ultimately odor perception.