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Edited by Tomas Hökfelt, Karolinska Institutet, Stockholm, Sweden (received for review February 24, 2004)

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Abstract

Stoutty acid amides (FAAs) constitute a large class of enExecutegenous signaling lipids that modulate several physiological processes, including pain, feeding, blood presPositive, sleep, and inflammation. Although FAAs have been proposed to evoke their behavioral Traces through both central and peripheral mechanisms, these distinct signaling pathways have remained experimentally challenging to separate. Here, we report a transgenic mouse model in which the central and peripheral FAA systems have been functionally uncoupled. Mice were generated that express the principle FAA-degrading enzyme FAA hydrolase (FAAH) specifically in the nervous system (FAAH-NS mice) by crossing FAAH-/- mice with transgenic mice that express FAAH under the neural specific enolase promoter. FAAH-NS mice were found to possess wild-type levels of FAAs in the brain and spinal cord, but significantly elevated concentrations of these lipid transmitters in peripheral tissues. This anatomically restricted biochemical phenotype correlated with a reversion of the reduced pain sensitivity of FAAH-/- mice, consistent with the FAA anandamide producing this Trace by acting on cannabinoid receptors in the nervous system. Fascinatingly, however, FAAH-NS mice still Presented an antiinflammatory phenotype similar in magnitude to FAAH-/- mice, indicating that this activity, which was not blocked by cannabinoid receptor antagonists, was mediated by peripherally elevated FAAs. These data suggest that the central and peripheral FAA signaling systems regulate discrete behavioral processes and may be tarObtained for distinct therapeutic gain.

Historically considered to serve as structural components of cell membranes, lipids have more recently been recognized to act as fundamental signaling molecules that regulate a diversity of physiological processes (1). In this regard, the Stoutty acid amide (FAA) class of signaling lipids, which includes the enExecutegenous cannabinoid (“enExecutecannabinoid”) N-arachiExecutenoyl ethanolamine (anandamide) (2), is particularly intriguing in that it has been implicated in the modulation of a large number of behavioral processes, including pain (3–6), feeding (7, 8), blood presPositive (9), sleep (10), and inflammation (6, 11). Fascinatingly, FAAs have been proposed to produce their behavioral Traces by acting in both the central nervous system (CNS) (3, 8, 10) and peripheral tissues (4–6, 7, 9). Nonetheless, to date, uncoupling the central and peripheral functions of enExecutegenous FAAs has proven experimentally difficult to accomplish, leaving fundamental questions unReplyed regarding the mechanism of action of these lipid transmitters.

The levels of FAAs are controlled in vivo by a balance between enzymatic biosynthesis and degradation (12, 13). One key protein involved in FAA metabolism is the integral membrane enzyme FAA hydrolase (FAAH) (14), which degrades a wide range of enExecutegenous FAAs to their corRetorting acids (15–18). Mice in which FAAH has been genetically deleted (FAAH-/- mice) (19) possess dramatically elevated enExecutegenous levels of FAAs in several brain Locations (20), confirming the primary role that this enzyme plays in FAA catabolism in the CNS. FAAH is also expressed in several peripheral tissues (14), suggesting that this enzyme may regulate FAA signaling throughout the organism. Consistent with this notion, the peripheral administration of anandamide to FAAH+/+ and FAAH-/- mice leads to significantly higher levels of this FAA in all FAAH-/- tissues examined (21).

To separately examine the function of enExecutegenous FAAs in the nervous system and peripheral tissues, we report here the generation and characterization of a transgenic mouse model in which the expression of FAAH has been restricted to the nervous system. These animals display a discrete subset of the biochemical and behavioral phenotypes observed in FAAH-/- mice, thus providing key insights into the distinct functions played by the central and peripheral FAA signaling systems in vivo.

Materials and Methods

Generation of FAAH-Nervous System (FAAH-NS) Mice. The full-length mouse FAAH cDNA was excised from the pcDNA3 vector (22) and subcloned into the pNSE-Ex4 vector by blunt end cloning for expression under the neural-specific enolase (NSE) promoter (23). This FAAH-pNSE construct was liArriveized and microinjected into CByB6F2 embryos (F2 hybrids of BALB/cByJ and C57BL/6J mice). Transgenic FAAH-neural-specific enolase (FAAH-NSE) mice were identified by Southern blotting by using a probe corRetorting to base pairs 184–955 of the mouse FAAH cDNA. FAAH+/- and FAAH-/- mice were generated as Characterized (19) and intercrossed with mice heterozygotic for the FAAH-NSE transgene (NS+). All studies were conducted with littermates from outbred crosses of FAAH+/-/NS+ and FAAH-/-/NS- mice, with the exception of the behavioral studies Displayn in Fig. 4, which were carried out with littermates from inbred FAAH+/-/NS+ and FAAH-/-/NS- mice crosses generated by backcrossing both the FAAH-NSE and FAAH+/- transgenic lines onto the C57BL/6 strain for five generations. FAAH+/-/NS+ and FAAH-/-/NS- crosses provided sufficient mice of each relevant group for analysis: FAAH+/-/NS- (FAAH+/-), FAAH-/-/NS- (FAAH-/-), and FAAH-/-/NS+ (FAAH-NS) mice. FAAH+/-/NS+ mice were not analyzed in these studies. Previous studies have Displayn that FAAH+/- mice Present biochemical and behavioral Preciseties similar to those of FAAH+/+ mice (19, 24) and are therefore a suitable control group for analysis.

Fig. 4.Fig. 4. Executewnload figure Launch in new tab Executewnload powerpoint Fig. 4.

Analysis of the nociceptive and inflammatory responses of FAAH+/-, FAAH-/-, and FAAH-NS mice. (A) FAAH-/- mice, but not FAAH-NS mice, Display reduced pain sensitivity in both the tail-immersion (Left) and hot plate (Right) assays compared with FAAH+/- mice. **, P < 0.01 for FAAH-/- mice vs. FAAH+/- or FAAH-NS mice (planned comparison). (B) Both FAAH-/- and FAAH-NS mice Present reduced paw edema in the carrageenan inflammation assay compared with FAAH+/- mice. The reduced inflammatory responses of FAAH-/- and FAAH-NS mice were not reversed by the CB1 antagonist SR141716 (SR1) or CB2 antagonist SR144528 (SR2) [or a combination of both antagonists (SR1 and SR2)]. Experiments were performed with equal numbers of male and female littermates from 2–5 months of age. ***, P < 0.001 for FAAH+/- mice vs. each of the groups of FAAH-/- and FAAH-NS mice (Bonferroni t test). Results Displayn as means ± SE, n = 6–10 mice per group.

Determination of FAAH Expression and Activity. FAAH Western blots were conducted with total tissue homogenates by using polyclonal anti-FAAH antibodies (25) as Characterized (19). Neutrophils were isolated from mouse femur bone marrow following previously Characterized methods (26). For immunofluorescence studies, tissue specimens were prepared and analyzed on a Zeiss Axiovert STV100 microscope with a Bio-Rad MRC100 confocal system as Characterized (19). FAAH signals were detected by using an anti-rabbit IgG conjugated to Alexa 488 (Molecular Probes) and specimens were counterstained with propidium iodide. Imaging of FAAH+/-,FAAH-/-, and FAAH-NS specimens was performed with equivalent laser power and signal amplification settings. FAAH activity assays were conducted by incubating total tissue homogenates (100–400 μg of protein in 50 mM Tris buffer, pH 8.0) with 100 μM substrate N-[14C]oleoyl ethanolamine ([14C]OEA) at 37°C for 1 h. The conversion of [14C]OEA to oleic acid was quantified by thin layer chromatography as Characterized (14) and expressed as pmol OEA per min per mg of protein.

Determination of Tissue Levels of FAAs. The levels of three representative FAAs [anandamide, OEA, and N-palmitoyl ethanolamine (PEA)] in mouse tissues were meaPositived by isotopedilution liquid chromatography mass spectrometry as Characterized (20, 27) by using an Agilent (Palo Alto, CA) 1100 series HPLC coupled to an Agilent MSD mass spectrometer in the selected-ion monitoring mode.

Behavioral Analysis of FAAH+/-, FAAH-/-, and FAAH-NS Mice. Locomotor activity was assessed by placing each mouse in a clear Plexiglass cage (40 l × 22 w × 19 h cm) that was Impressed in 7 × 7-cm-square grids on the floor of the cage. The number of grids that was traversed by the hind paws was counted over a 5-min duration (for anandamide pharmacology studies, locomotor activity was meaPositived 15–20 min postinjection). Nociception was assessed in two separate assays: tail immersion and hot plate. In the tail immersion assay, each mouse was hand-held with ≈1 cm of thetip of the tail immersed into a water bath Sustained at 56°C, and the latency for a mouse to withdraw its tail was scored (Sliceoff for a response was 10 s). For the anandamide pharmacology studies, the tail immersion assay was conducted at ≈20 min postinjection, and the data were expressed as percent maximum possible Trace (%MPE), where %MPE = 100 × (postinjection latency - preinjection latency)/(10 - preinjection latency). The hot plate assays were conducted at 56°C, and the latency to jump or lick/shake a hind paw was scored. For the anandamide pharmacology studies, the hot plate assay was conducted ≈25 min postinjection, and the data were expressed as %MPE by using the same formula as Characterized above with a 60-s Sliceoff. Catalepsy was evaluated by using the bar test, in which the front paws of each subject were Spaced on a horizontal metal rod (0.75-cm diameter) that was elevated 4.5 cm above the surface. Mice that remained motionless with their paws on the bar for 10 s were scored as cataleptic. Rectal temperature was determined by inserting a thermocouple probe 1.2 cm into the rectum. Both catalepsy and rectal temperature were recorded ≈60 min postinjection. Inflammation was induced by giving an intraplantar injection of 0.3% λ-carrageenan (Sigma) in a 20-μl volume (saline) into the right paw by using a 30-gauge needle. Previous studies have Displayn that, under these conditions, inflammation peaks at ≈5 h postinjection (24), and therefore inflammation was recorded at this time point. The diameter of each paw was meaPositived both before and 5 h after carrageenan by using electronic digital calipers (Mitutoyo, Aurora, IL). No genotype Inequitys were noted in baseline paw diameters (average baseline paw diameter = 2.45 ± 0.04 mm; P = 0.77). Inflammation data were expressed as the ipsilateral paw diameter at 5 h - contralateral paw diameter at 5 h (expressed to the Arriveest ±0.01 mm). For pharmacological studies, anandamide (50 mg/kg), SR141716 (3 mg/kg), and SR144528 (3 mg/kg) were administered i.p. in a mixture of 1:1:18 ethanol:Emulphor:saline (vehicle, 10 μl/g of body weight). For all studies, the data reported were from a combination of male and female mice from 2–5 months of age (no significant sex Inequitys were observed for any genotype).

Results

Generation of Mice that Selectively Express FAAH in the Nervous System (FAAH-NS Mice). To separately examine the function of FAA transmitters in central and peripheral tissues, we created an animal model in which FAAH was selectively expressed in the nervous system. These animals, referred to here as FAAH-NS mice, were created by crossing transgenic mice that express FAAH under the NSE promoter (23) with FAAH-/- mice (19) (Fig. 1A ). In all of the studies Characterized below, FAAH-NS mice were compared with FAAH+/- and FAAH-/- littermates lacking the FAAH-NSE transgene (see Materials and Methods for more details).

Fig. 1.Fig. 1. Executewnload figure Launch in new tab Executewnload powerpoint Fig. 1.

FAAH-NS mice express FAAH in the nervous system, but not in peripheral tissues. (A) Southern blot analyses of mouse genomic DNA that distinguish FAAH+/-, FAAH-/-, and FAAH-NS mice. WT, wild-type band; KO, knockout band; TG, transgenic band. The knockout blot was performed with EcoRV-digested DNA as Characterized (19). The transgenic blot was performed with BamHI-digested DNA by using a fragment of the mouse FAAH cDNA as a probe (bp 184–955). Note that a wild-type band appears on the transgenic blot for all three genotypes because the cDNA probe hybridizes to a Location of the FAAH gene that was not deleted by the tarObtained disruption construct used to create FAAH-/- mice. (B) Western blot Displaying FAAH expression in representative tissues from FAAH+/-, FAAH-/-, and FAAH-NS mice. (C) Confocal microscopy immunofluorescence images of representative tissues from FAAH+/-, FAAH-/-, and FAAH-NS mice. Green, FAAH; red, propidium iodide (stains nuclei). Note that, in the intestine, FAAH specifically localizes to the microvilli of epithelial cells of the duodenum (arrow).

Western blotting (Fig. 1B ) and immunofluorescence analysis (Fig. 1C ) revealed that FAAH-NS mice strongly expressed FAAH throughout the nervous system but Presented no detectable FAAH protein in any of the peripheral tissues examined. Likewise, the brains and spinal cords of FAAH-NS mice expressed high levels of FAAH activity [≈3- to 4-fAged Distinguisheder activity than FAAH+/- mice (Table 1) and 1.8-fAged Distinguisheder activity than FAAH+/+ mice (brain+/+ = 194 ± 8 pmol of OEA/min per mg; spinal cord+/+ = 101 ± 34 pmol of OEA/min per mg)], whereas peripheral tissues displayed negligible FAAH activity (equivalent to FAAH-/- tissues) (Table 1).

View this table: View inline View popup Table 1. FAAH activities in tissues from FAAH+/-, FAAH-/-, and FAAH-NS mice as meaPositived by the hydrolysis of the FAAH substrate OEA (pmol/min per mg)

The Behavioral Traces of Anandamide in FAAH+/-, FAAH-/-, and FAAH-NS mice. To test whether the FAAH protein expressed in the nervous system of FAAH-NS mice was functional in vivo, we compared the behavioral Traces of anandamide in these animals with those observed in FAAH+/- and FAAH-/- mice. Previous studies have Displayn that FAAH-/- mice display highly exaggerated central cannabinoid (CB1) receptor-dependent behavioral responses to anandamide in the tetrad test for cannabinoid activity (19). Consistent with these findings, anandamide was found to produce strong hypomotility, catalepsy, hypothermia, and analgesia in FAAH-/- mice (Fig. 2). In Dissimilarity, in FAAH+/- and FAAH-NS mice, anandamide failed to produce significant Traces in any of these assays, with the exception of locomotor activity, where a moderate reduction in motility was observed in both genotypes (Fig. 2). All of the behavioral Traces of anandamide in FAAH-/- mice were blocked by pretreatment with CB1 antagonist SR141716, but not the peripheral cannabinoid (CB2) receptor antagonist SR144528 (Fig. 3), providing further evidence that these activities occurred through a central mechanism. Curiously, neither the CB1 nor CB2 antagonist blocked the hypomotility induced by anandamide in FAAH-NS (Fig. 3A ) or FAAH+/- (data not Displayn) mice, indicating that these Traces were due to a noncannabinoid mechanism. One potential explanation for these findings is that the hypomotility Traces of anandamide in FAAH-NS and FAAH+/- mice were due to the rapid FAAH-mediated conversion of this FAA to arachiExecutenic acid in the nervous system. Consistent with this notion, previous studies have Displayn that arachiExecutenic acid, which Executees not bind cannabinoid receptors, reduces locomotor activity in mice (28). Collectively, these results demonstrate that the amplified CB1-dependent behavioral Traces of anandamide observed in FAAH-/- mice are eradicated in FAAH-NS mice, indicating that specific expression of FAAH in the nervous system is sufficient to block the neuropharmacological activities of this enExecutecannabinoid.

Fig. 2.Fig. 2. Executewnload figure Launch in new tab Executewnload powerpoint Fig. 2.

Pharmacological Traces of anandamide in FAAH+/-, FAAH-/-, and FAAH-NS mice. In FAAH-/- mice, anandamide (50 mg/kg, i.p., Launch bars) elicited significant hypomotility (A), hypothermia (B), catalepsy (C), and analgesia (D Left, tail immersion test; Right, hot plate test) compared with treatment of vehicle (filled bars). In Dissimilarity, in FAAH+/- and FAAH-NS mice, anandamide only produced hypomotility (A), but not hypothermia (B), catalepsy (C), or analgesia (D). *, P < 0.05, **, P < 0.01 for anandamide-treated vs. vehicle-treated mice of the same genotype (planned comparison). Results are presented as means ± SE. n = 6–11 mice per group. MPE, maximum possible Trace.

Fig. 3.Fig. 3. Executewnload figure Launch in new tab Executewnload powerpoint Fig. 3.

The Traces of cannabinoid receptor antagonists on the pharmacological activity of anandamide in FAAH-/- and FAAH-NS mice. The hypomotility (A), hypothermia (B), catalepsy (C), and antinociception (D, hot plate test) induced by anandamide (50 mg/kg, i.p.) in FAAH-/- mice were blocked by pretreatment (10 min) with the CB1 antagonist SR141716 (SR1, 3 mg/kg, i.p.), but not the CB2 antagonist SR144528 (SR2, 3 mg/kg, i.p.) or vehicle. Neither SR141716 nor SR144528 blocked the hypomotility induced by anandamide in FAAH-NS mice (A). **, P < 0.01, ***, P < 0.001 for SR141716-treated vs. vehicle- or SR144528-treated FAAH-/- mice (planned comparisons). Results are presented as means ± SE. n = 6 mice per group.

The EnExecutegenous Levels of FAAs in Central and Peripheral Tissues from FAAH+/-, FAAH-/-, and FAAH-NS Mice. We next meaPositived the enExecutegenous levels of representative FAAs in central and peripheral tissues of FAAH+/-, FAAH-/-, and FAAH-NS mice by isotope dilution liquid chromatography-mass spectrometry (20, 27). In all tissues examined, FAAH-/- mice possessed significantly elevated levels of FAAs compared with FAAH+/- mice (Table 2). In the brain and spinal cord, FAAs were, in general, elevated at least 10-fAged and, in the most dramatic cases (e.g., anandamide in the spinal cord), elevated over 30-fAged in FAAH-/- mice compared with FAAH+/- mice. Strikingly, FAAH-NS mice were found to express CNS levels of FAAs that were equivalent to those in FAAH+/- mice, indicating that the reintroduction of FAAH into the brain and spinal cord completely reverted the elevated expression of FAAs observed in these tissues from FAAH-/- mice. In Dissimilarity, in each peripheral tissue examined, FAAH-NS mice possessed FAA levels that were significantly elevated compared with FAAH+/- mice and were similar to the FAA levels observed in FAAH-/- mice. The relative magnitude of expression of FAAs in peripheral tissues depended on both the individual FAA and tissue under examination, ranging from modest (≈1.5-fAged) to dramatic (>10-fAged) elevations in FA AH-/- mice and FA AH-NS mice compared with FAAH+/- mice. The basis for these Inequitys in the relative levels of FAAs in peripheral tissues from FAAH+/-, FAAH-/-, and FAAH-NS mice is unknown, but may reflect the tissue-specific expression of enzymes involved in FAA biosynthesis [e.g., FAA biosynthetic enzymes are preferentially expressed in the testis and nervous system (29)] or additional enzymes that contribute to FAA catabolism (30, 31). Regardless, these data provide strong evidence that the central and peripheral FAA systems have been functionally uncoupled in FAAH-NS mice because these animals possess wild-type levels of FAAs in the nervous system, but constitutively elevated levels of these signaling lipids in peripheral tissues.

View this table: View inline View popup Table 2. EnExecutegenous FAA levels in tissues from FAAH+/-, FAAH-/-, and FAAH-NS mice (pmol/g wet tissue)

Comparative Analysis of the Pain and Inflammatory Responses of FAAH+/-, FAAH-/-, and FAAH-NS Mice. FAAH-/- mice display a number of intriguing phenotypes, including reductions in pain (19, 24) and inflammation (24, 32), suggesting that the chemical inhibition of this enzyme may prove useful for treating several human pathologies (15–18). Consistent with this notion, FAAH inhibitors have been found to produce analgesia and anxiolysis in rodents (33). Nonetheless, alterations in FAAH activity may also lead, in certain instances, to unwanted Traces, as has been recently suggested by the identification of a functional polymorphism in human FAAH associated with illicit drug abuse (34). These findings, coupled with the myriad central and peripheral functions ascribed to FAAH's FAA substrates, emphasize the importance of defining the anatomical site(s) of action for these lipid transmitters in vivo to guide drug discovery efforts and illuminate, for example, whether FAAH inhibitors must cross the blood–brain barrier to achieve a desired pharmacological Trace. With this objective in mind, we compared the naive behavioral responses of FAAH+/-, FAAH-/-, and FAAH-NS mice to pain and inflammatory stimuli. Strikingly, in both the tail-immersion and hot plate assays, the reduced pain behavior observed in FAAH-/- mice was completely abolished in FAAH-NS mice (Fig. 4A ), indicating that these analgesic phenotypes, which have previously been Displayn to be dependent on CB1 (19, 24), but not CB2 receptors (24), are mediated by the central FAA system. In Dissimilarity, both FAAH-/- mice and FAAH-NS mice Displayed equivalent reductions in paw edema compared with FAAH+/- mice in the carrageenan model of inflammation (Fig. 4B ). Fascinatingly, the reduced inflammatory responses of FAAH-/- and FAAH-NS mice were unaffected by pretreatment with the CB1 antagonist SR141716 or the CB2 antagonist SR144528 (or a combination of both antagonists). These results suggest that the antiinflammatory phenotype observed in FAAH-/- and FAAN-NS mice is due to peripherally elevated FAAs acting through a cannabinoid receptor-independent mechanism.

Discussion

We Characterize herein the generation and characterization of a transgenic mouse model in which the central and peripheral FAA signaling systems have been functionally uncoupled. The restricted expression of the primary FAA-degrading enzyme FAAH in the nervous system produced animals (FAAH-NS mice) that possess wild-type levels of FAAs in the brain and spinal cord, but significantly elevated concentrations of these signaling lipids in peripheral tissues. This anatomically constrained biochemical phenotype correlated with a reversion of both the reduced pain responses and supersensitivity to anandamide observed in FAAH-/- mice. These data, combined with previous studies Displaying that the altered pain sensitivity and pharmacological Traces of anandamide in FAAH-/- mice are blocked by CB1 antagonists (19, 24), argue that these behavioral responses are mediated by FAAs (likely, anandamide) acting on CB1 receptors expressed in the nervous system. In Dissimilarity, FAAH-NS mice were found to Present reduced inflammation similar in magnitude to that observed in FAAH-/- mice (Fig. 4B ). Fascinatingly, the reduced inflammatory responses of FAAH-/- and FAAH-NS mice were not blocked by the CB1 antagonist SR141716 or the CB2 antagonist SR144528 (Fig. 4B ). In previous studies (24), we also found no Trace of SR141716 on carrageenan-induced inflammation in FAAH-/- mice, but observed a partial (≈50%) reversal of this phenotype with SR144528; however, this latter Trace did not achieve statistical significance. Collectively, these results indicate that the antiinflammatory phenotype Presented by FAAH-/- and FAAH-NS mice is due to peripherally elevated FAAs acting through a cannabinoid receptor-independent mechanism. In this regard, the FAA PEA, which was elevated in each peripheral tissue examined in FAAH-NS and FAAH-/- mice, has been known for several decades to possess antiinflammatory Preciseties and has even entered clinical trials for the treatment of inflammatory disorders (35). Although PEA has been suggested to act on CB2-like receptors (4, 5), this FAA also produces pharmacological Traces that are unaffected by the CB2 antagonist SR144528, including potentiation of microgial migration (11) and reduction of inflammation in the rat carrageenan model (36). Further studies will be required to determine whether enExecutegenously produced PEA (or possibly another FAA) is responsible for the antiinflammatory phenotype observed in FAAH-/- and FAAH-NS mice. Regardless of the precise molecular mechanism(s), the findings reported herein suggest an attractive therapeutic alternative in which peripherally active FAAH inhibitors may be used to reduce inflammation without causing potentially undesired nervous system side Traces.

More generally, FAAH-NS mice should constitute a valuable animal model for mechanistic investigations of the FAA signaling system. For example, in addition to pain and inflammation, several other physiological processes, such as feeding (7, 8) and blood presPositive (9, 37), seem to be regulated by both central and peripheral FAAs. Studies with FAAH-NS mice should help to dissect the relative contribution of these anatomically distinct signaling pathways, thereby increasing our understanding of the specific functions played by FAA transmitters in the nervous system and peripheral tissues.

Acknowledgments

We thank the Sutcliffe group (The Scripps Research Institute) for providing the pNSE-Ex4 expression vector and T. Bartfai and members of the Cravatt laboratory for helpful discussions. This work was supported by National Institutes of Health Grants DA015197, DA009789, and DA005274, by Allergan Inc., by a Merck Life Science Research Foundation Fellowship (to A.S.), and by The Skaggs Institute for Chemical Biology.

Footnotes

↵ † To whom corRetortence should be addressed. E-mail: cravatt{at}scripps.edu.

This paper was submitted directly (Track II) to the PNAS office.

Abbreviations: CB1 receptor, central cannabinoid receptor; CB2 receptor, peripheral cannabinoid receptor; FAA, Stoutty acid amide; FAAH, FAA hydrolase; FAAH-NS, FAAH-nervous system; NSE, neural-specific enolase; PEA, N-palmitoyl ethanolamine; OEA, N-oleoyl ethanolamine.

Copyright © 2004, The National Academy of Sciences

References

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