The competitive CB1 antagonist/ inverse agonist SR141716A micro-injected into either the dorsolateral PAG or RVM also attenuates SIA. By con trast, inhibition of endocannabinoid hydrolysis at these sites enhances SIA . These data support the existence of supraspinal sites of endo cannabinoid analgesic action. Cannabinoids produce antinociception through spinal as well as supraspinal mechanisms . The antinociceptive and electrophysiological ef fects of cannabinoids are attenuated following spinal transec tion. Nonetheless, a long-lasting residual antinociception remains in spinally transected mice , suggesting the existence of spinal sites of endocannabi noid analgesic action. These data are consistent with the pres ence of CB1 receptors in the spinal dorsal horn . Intrathecally-administered cannabinoids also produce antino ciception and suppress noxious stimulus-evoked neuronal activity in spinal nociceptive neurons , suggesting a function al role for spinal cannabinoid receptors in modulating nociceptive processing. Intrathecal administration of either rimonabant or CB1 antisense oligonucleotides also elicits hyperalgesia , suggesting that endo cannabinoids may act tonically to suppress nociceptive responding. However, a physiological role for endocannabi noids at the spinal level has not been identified. Both 2-AG and anandamide fully qualify as endocannabi noids . These lipids are synthe sized and released on-demand, activate cannabinoid CB1 receptors with high affinity, and are metabolized in vivo by distinct hydrolytic pathways. Within the CNS, 2-AG is present in quantities 170e1000 times greater those of anandamide . 2-AG serves as a full agonist at CB1 and CB2 ,cannabis growing whereas anan damide is less efficacious . 2-AG is preferentially degraded by monoacylglycerol li pase , whereas anandamide is preferentially hydrolyzed by fatty-acid amide hydrolase.

Mutant mice lacking the FAAH gene are impaired in their ability to de grade anandamide and display reduced pain sensation that is reversed by the CB1 antagonist rimonabant . Immunocytochemical studies have revealed a heterogeneous distribution of FAAH through out the brain and moderate staining of FAAH-positive cells in the superficial dorsal horn of the spinal cord . In brain, the regional distribution of MGL partially overlaps with that of the CB1 receptor . Inhibition of MGL in the midbrain PAG increases 2-AG accumulation and enhances SIA in a CB1-dependent manner , supporting a physiological role for 2-AG in neural signaling. Thus, the anatomical distributions of FAAH and MGL are consistent with a role for these enzymes in terminating the activity of endocannabinoids. The present studies were conducted to investigate the con tribution of endocannabinoids acting at spinal CB1 receptors to nonopioid SIA. We used high-performance liquid chromatog raphy/mass spectrometry to examine the contribution of 2-AG and anandamide at the spinal level to SIA. We examined the time-course of changes in endocannabinoid lev els in the lumbar spinal cord of control rats and rats subjected to foot shock stress. Moreover, we used selective inhibitors of MGL and FAAH to further elucidate the roles of these en docannabinoids in SIA. We additionally evaluated effects of intrathecal administration of arachidonoylserotonin , a FAAH inhibitor that is inactive at phospholipase A2 and CB1 receptors, on SIA. We hypothe sized that intrathecal administration of these inhibitors would potentiate nonopioid SIA via a CB1 mechanism. Preliminary results have been reported .We have previously demonstrated that nonopioid SIA is mediated by mobilization of two endocannabinoids, 2-AG and anandamide, in the midbrain PAG . The present results extend those findings and suggest that endocannabinoid actions at spinal CB1 receptors modulate SIA. Foot shock stress induced time-dependent changes in the levels of 2-AG, but not anandamide, in the lumbar spinal cord. However, intrathecal administration of rimonabant failed to attenuate nonopioid SIA.

Nonetheless, selective inhibitors of MGL and FAAH, administered via the same route, increased both the magnitude and duration of SIA through a CB1- dependent mechanism. A parsimonious interpretation of these findings is that inhibition of MGL or FAAH prevented the de activation of spinal 2-AG and anandamide, respectively, mag nifying nonopioid SIA. Thus, our findings suggest that spinal endocannabinoids regulate, but do not mediate, nonopioid SIA. It is possible that the placement of chronic indwelling intrathecal catheters elevated anandamide levels in the behavioral studies, and that this change in endocannabinoid tone was augmented by the FAAH inhibitors. However, changes in endo cannabinoid tone due to catheter placement appear unlikely because intrathecal rimonabant administration did not alter tail-flick latencies in the presence or absence of foot shock. Moreover, Fos immunocytochemical studies suggest that spinal compression induced by catheter placement does not induce appreciable neuronal activation .Electrophysiological studies have provided evidence both for and against the existence of a tonic endocannabinoid tone at the spinal level. However, in our study, intrathecal rimonabant administration failed to suppress either basal noci ceptive thresholds or nonopioid SIA. Hyperalgesic effects of spinal rimonabant may reflect sensitivity of supraspinally-organized relative to spinally or ganized pain behaviors in measuring lowered nociceptive thresholds. It is also possible that exposure to un controlled stress mobilizes endocannabi noids in behavioral studies , thereby resulting in a CB1-dependent apparent hyperalgesia. Although high doses of anandamide activate transient re ceptor potential vanilloid 1 , several observations suggest that this mechanism is not responsible for the enhancements of SIA observed here. First, systemic administration of the TRPV1 antagonist capsazepine, at a dose that completely blocks capsaicin-induced antinociception, does not alter non opioid SIA in our paradigm . Second, CB1 and TRPV1 show minimal colocalization at the axonal level in the spinal cord, with CB1 localized predominantly to laminae I and II interneurons and TRPV1 localized primarily to nociceptive primary affer ent terminals . Third, anandamide activation of CB1 and TRPV1 typically induces opposing effects with distinct time courses .

However, we ob served only enhancementsdnot attenuationdof SIA follow ing intrathecal administration of FAAH inhibitors and no change in SIA following antagonist treatment. Fourth, rimona bant completely blocked the potentiation of SIA induced by intrathecal administration of inhibitors of MGL or FAAH, at doses that were insufficient to reverse SIA when administered alone. Together, these observations suggest that anandamide acts through CB1 rather than TRPV1 at the spinal level to modulate SIA. The foot shock-induced increases in 2-AG levels were smaller than those observed previously in the dorsal midbrain of the same subjects . This observation is consistent with the inability of spinally administered rimo nabant to block nonopioid SIA. By contrast, a tenfold lower dose of rimonabant produced a robust suppression of SIA when micro-injected into the dorsolateral PAG. Our results col lectively suggest that supraspinal sites of action play a pivotal role in endocannabinoid-mediated SIA. Our data suggest that spinal inhibition of MGL prolongs the duration of action of 2-AG, thereby enhancing endocannabi noid tone at spinal CB1 receptors to magnify SIA. This en hancement occurred in the absence of reliable changes in spinal anandamide levels. Thus, the antinociceptive effects of MGL inhibitors are not dependent upon concurrent eleva tions in anandamide that were induced in the midbrain PAG following exposure to the same stressor .However,cannabis grow tray foot shock did not reliably increase spinal anandamide levels. Our failure to observe en hancements in anandamide accumulation may reflect lower absolute levels of anandamide relative to 2-AG and conse quently higher variability in these measurements. Our data are consistent with the ability of FAAH inhibitors to selectively enhance accumulation of anandamide, but not 2-AG . FAAH may regulate both the distance endo cannabinoids diffuse to engage CB1 receptors and the duration of endocannabinoid actions to increase accumulation of tonically released anandamide. It is also pos sible that the extent of on-demand anandamide synthesis may be underestimated in the present work due to the rapid metab olism of this lipid by FAAH. Mapping the distribution of MGL, FAAH and CB1 in the spinal cord could further eluci date the anatomical and functional relationship between cells that degrade 2-AG and those expressing CB1. Cannabinoid receptor agonists such as D9 -tetrahydrocan nabinol have limited therapeutic applications at present, mainly because of their undesirable psychoactive effects. However, pharmacological agents that protect endocannabi noids such as 2-AG and anandamide from inactivation may lead to a more circumscribed spectrum of physiological re sponses than those produced by direct cannabinoid agonists. Ideally, this strategy would enhance endocannabinoid activity only at sites with on-going biosynthesis and release, thereby averting undesirable side effects. The possible use of drugs that inhibit endocannabinoid hydrolysis to treat pain in hu mans has thus propagated both hope and concern . FAAH is widely distributed throughout the body and implicated in the metabolism of a variety of anandamide analogues . Our data demonstrate that local enhancements of endocannabinoid actions at the spinal level are sufficient to potentiate SIA. Additional experiments will be necessary to determine whether inhibitors of endocannabinoid degrada tion may find therapeutic applications in the treatment of pain and stress-related disorders.Substance use disorders are among the most prevalent and costly psychiatric disorders in the United States.

The 12-month prevalence of alcohol use disorders among American adults was recently estimated at 8.46%, while the prevalence of drug use disorders was 2.0% . Individuals with SUDs often incur greater treatment costs than patients with chronic medical conditions and other behavioral health disorders . They also have an elevated risk of negative psychosocial outcomes, including intimate-partner and non-partner violence , incarceration , and absenteeism from work . Among individuals diagnosed with a SUD, the prevalence of other psychiatric disorders is greater than in the general population. In recent epidemiological research the prevalence of mood disorders among those with SUDs was 20.13%, compared to 8.19% for the non substance-disordered population . Major depressive disorder is the most common co-occurring disorder, with a prevalence of 15.5% among individuals diagnosed with a SUD. Although many types of co-occurring conditions are associated with negative outcomes, the additional burdens associated with MDD have been especially well-characterized. Patients with SUD and MDD incur substantially greater costs in mental health, substance abuse, and medical care and utilize high-cost emergency department and inpatient care more frequently . The annual cost of treating a patient with SUD and MDD has been estimated at $5,318, compared to $1,246 for those with a SUD alone . In addition to these excess cost burdens, having MDD in addition to SUD is associated with a multitude of negative psychosocial outcomes, including greater risk of suicide attempts , worse quality of life , and higher rates of social problems and work disability. Pre-treatment levels of problem severity across multiple domains are often worse for patients with SUD and MDD . Perhaps the most important clinical characteristic of adults with SUD and MDD is evidence that they typically have poorer outcomes from treatment for substance use. In naturalistic studies of inpatient alcohol treatment, having MDD at baseline predicted earlier relapse and greater post-treatment depressive symptoms were associated with a greater risk of relapse . In Project MATCH greater depressive symptoms predicted poorer drinking outcomes, and in patients with alcohol and tobacco dependence, depressive symptoms predicted non-abstinence and level of drinking at every follow-up assessment . Findings are similar in studies of treatment for users of illicit drugs. Cocaine dependent patients with MDD have exhibited poorer outcomes from cognitive-behavioral therapy . In the Methamphetamine Treatment Project, greater severity of depressive symptoms predicted poorer adherence and worse treatment outcomes, and patients with MDD had more frequent methamphetamine use and lower odds of abstinence at follow-up. Among adolescents in marijuana dependence treatment, MDD was associated with a greater likelihood of relapse and more total relapses . Adults with SUD and MDD may resist participation in community 12-step activities and derive less benefit from 12-step involvement . Although some past studies found no relationship between depression and substance use treatment outcomes, there is a growing body of evidence supporting the negative impact of depression on treatments for various substances in a variety of settings. Historically, those with substance dependence and a co-occurring psychiatric disorder could not receive integrated treatments that simultaneously target both disorders in a single setting . More recently, researchers have advocated for the evaluation and implementation of integrated treatments that could be superior to treatments that target substance use alone . However, very few well designed studies have examined the efficacy of integrated treatment for substance dependence and MDD, with a recent meta-analysis identifying only five controlled trials comparing integrated treatment to treatment of substance use alone . Overall, integrated treatments performed significantly better on substance use outcomes, but not on depression or retention.