Comparative analysis of fatty acid amide hydrolase and cb1 cannabinoid receptor expression in the mouse brain: evidence of a widespread role for fatty acid amide hydrolase in regulation of endocannabinoid signaling

doi:10.1016/S0306-4522(03)00145-3

Neuroscience

Volume 119, Issue 2, 27 June 2003, Pages 481-496

https://doi.org/10.1016/S0306-4522(03)00145-3 Get rights and content

Abstract

Fatty acid amide hydrolase (FAAH) catalyses hydrolysis of the endocannabinoid arachidonoylethanolamide (“anandamide”) in vitro and regulates anandamide levels in the brain. In the cerebellar cortex, hippocampus and neocortex of the rat brain, FAAH is located in the somata and dendrites of neurons that are postsynaptic to axon fibers expressing the CB₁ cannabinoid receptor [Proc R Soc Lond B 265 (1998) 2081]. This complementary pattern of FAAH and CB₁ expression provided the basis for a hypothesis that endocannabinoids may function as retrograde signaling molecules at synapses in the brain [Proc R Soc Lond B 265 (1998) 2081; Phil Trans R Soc Lond 356 (2001) 381] and subsequent experimental studies have confirmed this [Science 296 (2002) 678]. To assess more widely the functions of FAAH in the brain and the potential impact of FAAH activity on the spatiotemporal dynamics of endocannabinoid signaling in different regions of the brain, here we have employed immunocytochemistry to compare the distribution of FAAH and CB₁ throughout the mouse brain, using FAAH^−/− mice as negative controls to validate the specificity of FAAH-immunoreactivity observed in wild type animals. In many regions of the brain, a complementary pattern of FAAH and CB₁ expression was observed, with FAAH-immunoreactive neuronal somata and dendrites surrounded by CB₁-immunoreactive fibers. In these regions of the brain, FAAH may regulate postsynaptic formation of anandamide, thereby influencing the spatiotemporal dynamics of retrograde endocannabinoid signaling. However, in some regions of the brain such as the globus pallidus and substantia nigra pars reticulata, CB₁ receptors are abundant but with little or no associated FAAH expression and in these brain regions the spatial impact and/or duration of endocannabinoid signaling may be less restricted than in regions enriched with FAAH. A more complex situation arises in several regions of the brain where both FAAH and CB₁ are expressed but in a non-complementary pattern, with FAAH located in neurons and/or oligodendrocytes that are proximal but not postsynaptic to CB₁-expressing axon fibers. Here FAAH may nevertheless influence endocannabinoid signaling but more remotely. Finally, there are regions of the brain where FAAH-immunoreactive neurons and/or oligodendrocytes occur in the absence of CB₁-immunoreactive fibers and here FAAH may be involved in regulation of signaling mediated by other endocannabinoid receptors or by receptors for other fatty acid amide signaling molecules. In conclusion, by comparing the distribution of FAAH and CB₁ in the mouse brain, we have provided a neuroanatomical framework for comparative analysis of the role of FAAH in regulation of the spatiotemporal dynamics of retrograde endocannabinoid signaling in different regions of the brain.

Section snippets

Experimental procedures

Preliminary immunocytochemical analysis of FAAH and CB₁ expression was performed using brains from mice of the BALB/c strain to establish working methods prior to analysis of brains from FAAH-knockout mice (FAAH^−/−) and their wild type littermates (FAAH^+/+). FAAH^−/− and FAAH^+/+ mice were produced from intercrosses of 129SvJ-C57BL/6 FAAH^+/− mice at the Scripps Research Institute, as described by Cravatt et al. (2001). Three pairs of mice were analysed at ages between 12 and 16 weeks: 680/681

General observations

Immunocytochemical analysis of FAAH expression in sections of wild type mouse brain revealed a pattern of immunostaining (Fig. 1) that was generally consistent with the distribution of FAAH mRNA expression in rat brain (Thomas et al., 1997). Moreover, to establish unequivocally the specificity of the immunostaining observed with the FAAH antibodies in the mouse brain, we analyzed brain sections from FAAH^−/− mice alongside brain sections from their wild type littermates. Importantly, all of the

Discussion

Here we report the first detailed analysis of the distribution of FAAH in the mouse brain, using FAAH^−/− mice as negative controls to provide an unequivocal determination of the specificity of immunostaining in wild type animals. The majority of FAAH in the mouse brain is associated with neurons and it is the presence of FAAH in neurons that is probably most directly relevant to endocannabinoid signaling, as discussed below. An interesting feature of neuronal FAAH-immunostaining in several

Acknowledgements

This work was supported by a Wellcome Trust grant (057058) awarded to M.R.E. We are grateful to Kristin Demarest (TSRI) for technical assistance and to John Priestley (QMUL) for use of his digital photomicroscope. We are also grateful to Swidbert Ott (QMUL) for help and advice with digital photomicroscopy and to two anonymous reviewers for their constructive criticism of the manuscript.

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For PF7845-yne, fluorescent drug signal can be observed throughout the cortical region, thalamus, amygdala, with the highest abundance in the hippocampus (Figure 5). As FAAH is a membrane protein (Egertová et al., 2003), drug binding would appear as membrane like structure when examined at sufficient resolution (for example, in Figure 6, at 2.49 micron/pixel in-plane resolution). CATCH allows for high resolution covalent drug binding mapping in intact tissue.
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NeuropharmacologyComparative analysis of fatty acid amide hydrolase and cb1 cannabinoid receptor expression in the mouse brain: evidence of a widespread role for fatty acid amide hydrolase in regulation of endocannabinoid signaling

Abstract

Section snippets

Experimental procedures

General observations

Discussion

Acknowledgements

Neurosci Lett

FEBS Letters

Neuron

Curr Opin Neurobiol

Neurosci Res

Neuron

Neuron

Neurosci Lett

Neuroscience

Evidence for a new G protein-coupled cannabinoid receptor in mouse brain

Mol Pharmacol

Endocannabinoids facilitate the induction of LTP in the hippocampus

Nat Neurosci

Chemical characterization of a family of brain lipids that induce sleep

Science

Molecular characterization of an enzyme that degrades neuromodulatory fatty-acid amides

Nature

Supersensitivity to anandamide and enhanced endogenous cannabinoid signaling in mice lacking fatty acid amide hydrolase

Proc Natl Acad Sci USA

Brain monoglyceride lipase participating in endocannabinoid inactivation

Proc Natl Acad Sci USA

Localisation of cannabinoid receptors in the rat brain using antibodies to the intracellular C-terminal tail of CB1

J Comp Neurol

A new perspective on cannabinoid signallingcomplementary localization of fatty acid amide hydrolase and the CB1 receptor in rat brain

Proc R Soc Lond B

Neuropharmacology
Comparative analysis of fatty acid amide hydrolase and cb₁ cannabinoid receptor expression in the mouse brain: evidence of a widespread role for fatty acid amide hydrolase in regulation of endocannabinoid signaling

Localisation of cannabinoid receptors in the rat brain using antibodies to the intracellular C-terminal tail of CB₁

A new perspective on cannabinoid signallingcomplementary localization of fatty acid amide hydrolase and the CB₁ receptor in rat brain