Cannabinoid Control of Olfactory Processes: The Where Matters

Abstract

Olfaction has a direct influence on behavior and cognitive processes. There are different neuromodulatory systems in olfactory circuits that control the sensory information flowing through the rest of the brain. The presence of the cannabinoid type-1 (CB1) receptor, (the main cannabinoid receptor in the brain), has been shown for more than 20 years in different brain olfactory areas. However, only over the last decade have we started to know the specific cellular mechanisms that link cannabinoid signaling to olfactory processing and the control of behavior. In this review, we aim to summarize and discuss our current knowledge about the presence of CB1 receptors, and the function of the endocannabinoid system in the regulation of different olfactory brain circuits and related behaviors.

Modulation of olfactory signal detection in the olfactory epithelium: focus on the internal and external environment, and the emerging role of the immune system

“…Similarly, application of neuropeptide Y (NPY), an orexigenic peptide, increases the electrophysiological response of OSNs, but only in fasted rats (Negroni et al 2012). Endocannabinoids, which impact energy metabolism and feeding behaviour, have been also investigated for their functional importance in the olfactory system (reviewed Terral et al 2020). Endocannabinoids exert contrasting effects depending on the species and differences between mammalian and other vertebrates are noticed: an endocannabinoid system was first described in the tadpole OE with a neuronal expression of CB1 receptors and endocannabinoid 2-arachidonoylglycerol synthesis in both neurons and SCs (Czesnik et al 2007;Breunig et al 2010).…”

Endocannabinoid‐mediated neuromodulation in the main olfactory bulb at the interface of environmental stimuli and central neural processing

“…Based on the CB1R expression pattern and the impact of olfactory acuity on cognition and behavior, analysis and investigation of the function of the endocannabinoid system in regulating different olfactory brain circuits and related behaviors is progressing rapidly (Terral et al., 2020). Experimental evidence in this regard has come primarily from rodent models of various neurodegenerative and neuropsychiatric disorders (Bhatia‐Dey & Heinbockel, 2020; Hutch et al., 2015; Pouille & Schoppa, 2018; Soria‐Gómez et al., 2014).…”

Cannabinoids Regulate Sensory Processing in Early Olfactory and Visual Neural Circuits

“…While the basic signaling functions of the endocannabinoid system are understood relatively well in limbic structures such as the hippocampus and the amygdala, this signaling system is less well understood in the olfactory pathway (Terral et al, 2020 ; Heinbockel et al, 2021 ) and visual system. Here, we describe the early olfactory and visual pathways and compare and contrast endocannabinoids as signaling molecules in them and the relevance of the endocannabinoid system for synaptic plasticity.…”

“…Other studies have established additional functional consequences of CB 1 -mediated regulation in the main olfactory bulb. Cannabinoid signaling in the main olfactory bulb can regulate appetite and adjust the olfactory threshold through centrifugal fiber input to inhibitory granule cells as a means of cortical feedback to the main olfactory bulb (Soria-Gómez et al, 2014 ; Pouille and Schoppa, 2018 ; Terral et al, 2020 ). In a key article, showed that feeding behavior can be regulated by eCBs in the olfactory system such that CB 1 increases feeding behavior in fasted mice (hyperphagia) through enhanced detection of food, mediated by olfactory mechanisms (Soria-Gómez et al, 2014 ).…”