Journal article
Distribution of CB1 cannabinoid receptors and their relationship with mu-opioid receptors in the rat periaqueductal gray
Neuroscience, Vol.213, pp.191-200
06/28/2012
Handle:
https://hdl.handle.net/2376/106767
PMCID: PMC3367071
PMID: 22521830
Abstract
► CB1 receptor expression is diffuse and extensive in the periaqueductal gray (PAG). ► The mu-opioid peptide (MOP) and CB1 receptors co-localize in many PAG neurons. ► CB1 labeling was mostly somatodendritic, but CB1 axon terminals were also detected. ► The pattern and extent of CB1 labeling was similar in the dlPAG and vlPAG. ► Chronic morphine or THC administration had no effect on CB1 receptor density.
The periaqueductal gray (PAG) is part of a descending pain modulatory system that, when activated, produces widespread and profound antinociception. Microinjection of either opioids or cannabinoids into the PAG elicits antinociception. Moreover, microinjection of the cannabinoid 1 (CB1) receptor agonist HU-210 into the PAG enhances the antinociceptive effect of subsequent morphine injections, indicating a direct relationship between these two systems. The objective of this study was to characterize the distribution of CB1 receptors in the dorsolateral and ventrolateral PAG in relationship to mu-opioid peptide (MOP) receptors. Immunocytochemical analysis revealed extensive and diffuse CB1 receptor labeling in the PAG, 60% of which was found in somatodendritic profiles. CB1 and MOP receptor immunolabeling were co-localized in 32% of fluorescent Nissl-stained cells that were analyzed. Eight percent (8%) of PAG neurons that were MOP receptor-immunoreactive (-ir) received CB1 receptor-ir appositions. Ultrastructural analysis confirmed the presence of CB1 receptor-ir somata, dendrites and axon terminals in the PAG. These results indicate that behavioral interactions between cannabinoids and opioids may be the result of cellular adaptations within PAG neurons co-expressing CB1 and MOP receptors.
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Details
- Title
- Distribution of CB1 cannabinoid receptors and their relationship with mu-opioid receptors in the rat periaqueductal gray
- Creators
- A.R Wilson-Poe - Department of Neuroscience, Washington State University, 14204 NE Salmon Creek Avenue, Vancouver, WA 98686, USAM.M Morgan - Department of Neuroscience, Washington State University, 14204 NE Salmon Creek Avenue, Vancouver, WA 98686, USAS.A Aicher - Department of Physiology and Pharmacology, Oregon Health & Science University, Mail code: L334, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USAD.M Hegarty - Department of Physiology and Pharmacology, Oregon Health & Science University, Mail code: L334, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
- Publication Details
- Neuroscience, Vol.213, pp.191-200
- Academic Unit
- Psychology, Department of
- Publisher
- Elsevier Ltd
- Identifiers
- 99900546984501842
- Language
- English
- Resource Type
- Journal article