Cannabinoid receptors in the human brain: a detailed anatomical and quantitative autoradiographic study in the fetal, neonatal and adult human brain

GABA Targets for the Treatment of Cognitive Dysfunction in Schizophrenia

Cognitive deficits, including impairments in working memory that have been linked to the prefrontal cortex, are among the most debilitating and difficult to treat features of schizophrenia. Consequently, the identification of potential targets informed by the pathophysiology of the illness is needed to develop novel pharmacological approaches for ameliorating these deficits. Postmortem studies of the prefrontal cortex in schizophrenia subjects have revealed disturbances restricted to a subpopulation of inhibitory neurons that includes chandelier neurons, whose axon terminals synapse on the axon initial segment of pyramidal neurons. Chandelier neurons play an important role in synchronizing pyramidal neuron activity and appear to be a critical component of the prefrontal cortical circuitry that subserves working memory function. Therefore, in this paper we review evidence suggesting that drugs which selectively enhance chandelier neuron-mediated inhibition of prefrontal pyramidal neurons may improve working memory dysfunction in schizophrenia. Potential novel targets for such agents include GABA(A) receptors that contain the α(2) subunit. In addition, we discuss potential complementary mechanisms for enhancing inhibitory input to pyramidal cell bodies, including drugs with activity at the CB1 receptor of the endocannabinoid system. The development of pathophysiologically-based treatments that selectively remediate disturbances in specific neural circuits underlying working memory may provide an effective approach to improving cognitive deficits in schizophrenia.

Redistribution of CB1 cannabinoid receptors during evolution of cholinergic basal forebrain territories and their cortical projection areas: A comparison between the gray mouse lemur (Microcebus murinus, primates) and rat

Endocannabinoid signaling, mediated by presynaptic CB1 cannabinoid receptors on neurons, is fundamental for the maintenance of synaptic plasticity by modulating neurotransmitter release from axon terminals. In the rodent basal forebrain, CB1 cannabinoid receptor-like immunoreactivity is only harbored by a subpopulation of cholinergic projection neurons. However, endocannabinoid control of cholinergic output from the substantia innominata, coincident target innervation of cholinergic and CB1 cannabinoid receptor-containing afferents, and cholinergic regulation of endocannabinoid synthesis in the hippocampus suggest a significant cholinergic-endocannabinergic interplay. Given the functional importance of the cholinergic modulation of endocannabinoid signaling, here we studied CB1 cannabinoid receptor distribution in cholinergic basal forebrain territories and their cortical projection areas in a prosimian primate, the gray mouse lemur. Perisomatic CB1 cannabinoid receptor immunoreactivity was unequivocally present in non-cholinergic neurons of the olfactory tubercule, and in cholecystokinin-containing interneurons in layers 2/3 of the neocortex. Significantly, CB1 cannabinoid receptor-like immunoreactivity was localized to cholinergic perikarya in the magnocellular basal nucleus. However, cortical cholinergic terminals lacked detectable CB1 cannabinoid receptor levels. A dichotomy of CB1 cannabinoid receptor distribution in frontal (suprasylvian) and parietotemporal (subsylvian) cortices was apparent. In the frontal cortex, CB1 cannabinoid receptor-containing axons concentrated in layers 2/3 and layer 6, while layer 4 and layer 5 were essentially devoid of CB1 cannabinoid receptor immunoreactivity. In contrast, CB1 cannabinoid receptors decorated axons in all layers of the parietotemporal cortex with peak densities in layer 2 and layer 4. In the hippocampus, CB1 cannabinoid receptor-containing terminals concentrated around pyramidal cell somata and proximal dendrites in the CA1-CA3 areas, and granule cell dendrites in the molecular layer of the dentate gyrus. CB1 cannabinoid receptors frequently localized to inhibitory GABAergic terminals while leaving glutamatergic boutons unlabeled. Aging did not affect either the density or layer-specific distribution of CB1 cannabinoid receptor-immunoreactive processes. We concluded that organizing principles of CB1 cannabinoid receptor-containing neurons and their terminal fields within the basal forebrain are evolutionarily conserved between rodents and prosimian primates. In contrast, the areal expansion and cytoarchitectonic differentiation of neocortical subfields in primates is associated with differential cortical patterning of CB1 cannabinoid receptor-containing subcortical and intracortical afferents.

The endocannabinoid system and the treatment of obesity

The endocannabinoids are endogenous lipids capable of binding to both cannabinoid receptors (CB) CB1 and CB2. These receptors belong to the G protein-coupled family receptors and they were discovered while investigating the mode of action of ?(9)-tetrahydrocannabinol, a component of Cannabis sativa, to which they bind with high affinity. Among many other brain sites, CB1 is present in the hypothalamic nuclei involved in the control of energy balance and body weight, as well as in neurons of the mesolimbic system which is believed to mediate the incentive value of food. At central nervous system level, CB1 activation is necessary to induce food intake after a short period of food deprivation, and when CB1 is activated by endocannabinoids produced in situ, a stimulation of the ingestion of palatable food has been described. CB1 stimulation leads to modulation of the release of some hypothalamic anorexigenic and orexigenic mediators, as well as of dopamine in the nucleus accumbens shell. Recent evidence has proved that CB1 is also present in the peripheral organs, such as the adipose tissue and gastrointestinal system, key organs in the regulation of energy metabolism. Animal models have provided solid evidence that genetically induced obesity leads to long-lasting overstimulation of endocannabinoid system synthesis resulting in permanent overactivation of CB1, which may then contribute to the maintenance of this disease. Importantly, at peripheral level, CB1 activation has been shown to stimulate lipogenesis in adipocytes. CB1 blockers increase adiponectin production in adipocytes, which leads to increased fatty acid oxidation and free fatty acid clearance. Moreover, CB1 has been shown to be up-regulated in adipocytes derived from obese rodents. These results support the role of endocannabinoids in the development and maintenance of obesity, paving the way for the development of a new class of drugs such as the CB1 blockers as a therapy for tackling obesity and the associated major cardiovascular risk factors.

Cannabinoid suppressed bicuculline-induced convulsion without respiratory depression in the brainstem-spinal cord preparation from newborn rats

Previous studies have suggested that cannabinoid compounds are anticonvulsants and that these compounds depress respiratory activity. However, the anticonvulsant potential of cannabinoids and their depressive effect on respiration have not been evaluated simultaneously. In the present study, we used a brainstem-spinal cord preparation model to investigate changes in inspiratory activity and the anticonvulsant effects of a cannabinoid receptor agonist, WIN 55, 212-2, in bicuculline-induced convulsion. Application of 10 microM WIN 55, 212-2 caused no change in inspiratory activity (6.9+/- 0.89 bursts/min vs. 8.0+/- 1.3 bursts/min, not significant) and decreased bicuculline-induced seizure-like nerve activity (number of seizure-like activities in 10 min, 11+/- 7.4 bursts vs. 1.5+/- 1.6 bursts, P< 0.01; average duration of seizure-like activity, 8.9+/- 4.0 sec vs. 4.7+/- 2.1 sec, P> 0.01). Our results suggest that administration of an appropriate dose of cannabinoid receptor agonist WIN 55,212-2 has an anticonvulsant effect but does not cause respiratory depression.

Cannabinoid physiology and pharmacology: 30 years of progress

Delta9-Tetrahydrocannabinol from Cannabis sativa is mimicked by cannabimimetic analogs such as CP55940 and WIN55212-2, and antagonized by rimonabant and SR144528, through G-protein-coupled receptors, CB1 in the brain, and CB2 in the immune system. Eicosanoids anandamide and 2-arachidonoylglycerol are the "endocannabinoid" agonists for these receptors. CB1 receptors are abundant in basal ganglia, hippocampus and cerebellum, and their functional activity can be mapped during behaviors using cerebral metabolism as the neuroimaging tool. CB1 receptors couple to G(i/o) to inhibit cAMP production, decrease Ca2+ conductance, increase K+ conductance, and increase mitogen-activated protein kinase activity. Functional activation of G-proteins can be imaged by [35S]GTPgammaS autoradiography. Post-synaptically generated endocannabinoids form the basis of a retrograde signaling mechanism referred to as depolarization-induced suppression of inhibition (DSI) or excitation (DSE). Under circumstances of sufficient intracellular Ca2+ (e.g., burst activity in seizures), synthesis of endocannabinoids releases a diffusible retrograde messenger to stimulate presynaptic CB1 receptors. This results in suppression of gamma-aminobutyric acid (GABA) release, thereby relieving the post-synaptic inhibition. Tolerance develops as neurons adjust both receptor number and cellular signal transduction to the chronic administration of cannabinoid drugs. Future therapeutic drug design can progress based upon our current understanding of the physiology and pharmacology of CB1, CB2 and related receptors. One very important role for CB1 antagonists will be in the treatment of craving in the disease of substance abuse.

Effects of nicotine and a cannabinoid receptor agonist on negative contrast: distinction between anxiety and disappointment?

RATIONALE

Animals trained to lick for a sucrose solution of a given incentive value that subsequently encounter an incentive downshift (i.e. 32-4% sucrose) display an exaggerated decrease in the amount consumed, relative to unshifted controls. This change has been classified as a successive negative contrast (SNC) effect. The emotional component to this robust behavioural change is dynamic and changes from post-shift day (PSD) 1 to 2. Anxiolytics block SNC, but the possible link between anxiety and SNC needs further exploration. Both nicotine and a cannabinoid receptor agonist have been reported to change anxiety and both have actions on the reward process, but their effects on SNC have not been investigated.

OBJECTIVES

To determine: (1) whether exposure to SNC evokes an anxiogenic response; (2) whether an anxiolytic dose of nicotine has the same effects on SNC as those of chlordiazepoxide; (3) the effects of a low (anxiolytic) and a high (anxiogenic) dose of the cannabinoid receptor agonist CP 55,940 on SNC.

METHODS

Two groups of animals were given access to high (32%) or low (4%) sucrose solutions for 5 min per day for 10 days. On PSD 1 and 2, the shifted group had access to a devalued incentive (from 32 to 4% sucrose) and the unshifted group remained at 4% sucrose. The volumes (ml) of sucrose solution consumed were measured pre-shift and on PSD 1 and 2. In experiment 1, immediately after SNC testing on PSD 1 and 2, the rats were tested in the social interaction and elevated plus-maze tests of anxiety. In experiment 2, the effects of chlordiazepoxide (5 and 7.5 mg/kg) and nicotine (0.1 mg/kg) were examined on PSD 1 and 2. In experiment 3, the effects of CP 55,940 (5 and 40 microg/kg) were examined on PSD 1 and 2.

RESULTS

There were no anxiogenic effects of shift in either test of anxiety on either test day. However, on PSD 1, the shifted group had significantly higher locomotor activity and spent a higher percentage of time on the open arms, perhaps reflecting search strategies. Nicotine was without significant effect on SNC on either test day. On PSD 1, chlordiazepoxide (5 mg/kg) and CP 55,940 (5 and 40 microg/kg, IP) blocked SNC. On PSD 2, both doses of chlordiazepoxide and the low, anxiolytic dose of CP 55,940 (5 microg/kg) blocked SNC, the high dose of CP 55,940 was without effect.

CONCLUSIONS

The pattern of results allows for the separation between effects on anxiety and SNC. The block of contrast on PSD 1 was independent of changes in anxiety, since both anxiolytic and anxiogenic drug doses were effective. It is suggested that this may provide an animal model of disappointment in which the cannabinoid system plays an important role. An anxiolytic action would seem to be a necessary, but not a sufficient, action to block SNC on PSD 2.

Cerebrospinal anandamide levels are elevated in acute schizophrenia and are inversely correlated with psychotic symptoms

The endocannabinoids are a family of bioactive lipids that activate CB1 cannabinoid receptors in the brain and exert intense emotional and cognitive effects. Here, we have examined the role of endocannabinoid signaling in psychotic states by measuring levels of the endocannabinoid anandamide in cerebrospinal fluid (CSF) of acute paranoid-type schizophrenic patients. We found that CSF anandamide levels are eight-fold higher in antipsychotic-naive first-episode paranoid schizophrenics (n = 47) than healthy controls (n = 84), dementia patients (n = 13) or affective disorder patients (n = 22). Such an alteration is absent in schizophrenics treated with 'typical' antipsychotics (n = 37), which antagonize dopamine D2-like receptors, but not in those treated with 'atypical' antipsychotics (n = 34), which preferentially antagonize 5HT(2A) receptors. Furthermore, we found that, in nonmedicated acute schizophrenics, CSF anandamide is negatively correlated with psychotic symptoms (rS = -0.452, P = 0.001). The results suggest that anandamide elevation in acute paranoid schizophrenia may reflect a compensatory adaptation to the disease state.

Characterization of the endocannabinoid system in early human pregnancy

In recent years, it has been demonstrated that high circulating levels of the endogenous cannabinoid anandamide, resulting from low expression of its metabolizing enzyme fatty acid amide hydrolase (FAAH), may contribute to spontaneous miscarriage and poor outcome in women undergoing in vitro fertilization. The site of action of this compound, however, has not been determined. In this study, we examined the distribution of the cannabinoid receptors, CB1 and CB2, and the endocannabinoid-metabolizing enzyme FAAH in first trimester human placenta. Here, we show that FAAH is expressed throughout the human first trimester placenta, in extravillous trophoblast columns, villous cytotrophoblasts, syncytiotrophoblasts, and macrophages. Furthermore, FAAH mRNA levels appear to be regulated during gestation, with levels peaking at 11 wk before declining again. The immune system-associated cannabinoid CB2 receptors were localized only to placental macrophages. Interestingly, the cannabinoid receptor CB1 was not identified in first trimester placenta despite having previously been shown to be present in placental tissues at term. These findings suggest that the placenta may form a barrier preventing maternal-fetal transfer of anandamide and/or modulate local levels of anandamide by regulation of FAAH expression with gestation.

Immunohistochemical characterisation and localisation of cannabinoid CB1 receptor protein in the rat vestibular nucleus complex and the effects of unilateral vestibular deafferentation

CB1 receptor expression has been reported to be low in the brainstem compared with the forebrain, and low in the vestibular nucleus complex (VNC) compared with other regions in the brainstem. However, a frequent effect of cannabis is dizziness and loss of balance. This may be due to the activation of cannabinoid receptors in the central vestibular pathways. We used immunohistochemistry to study the distribution of CB1 receptor protein in the VNC, and Western blotting to measure CB1 receptor expression in the VNC following unilateral vestibular deafferentation (UVD); the hippocampal CA1, CA2/3 and dentate gyrus (DG) regions were also analysed for comparison. This study confirms a previous electrophysiological demonstration that CB1 receptors exist in significant densities in the VNC and are likely to contribute to the neurochemical control of the vestibular reflexes. Nonetheless, CB1 receptor expression did not change significantly in the VNC during vestibular compensation. In addition, despite some small but significant changes in CB1 receptor expression in the CA2/3 and the DG following UVD, in no case were these differences statistically significant in comparison to both control groups.

Differential loss of striatal projection systems in Huntington's disease: a quantitative immunohistochemical study

Prior studies suggest differences exist among striatal projection neuron types in their vulnerability to Huntington's disease (HD). In the present study, we immunolabeled the fibers and terminals of the four main types of striatal projection neuron in their target areas for substance P, enkephalin, or glutamic acid decarboxylase (GAD), and used computer-assisted image analysis to quantify the abundance of immunolabeled terminals in a large sample of HD cases ranging from grade 0 to grade 4 [J. Neuropathol. Exp. Neurol. 44 (1985) 559], normalized to labeling in control human brains. Our goal was to characterize the relative rates of loss of the two striatopallidal projection systems (to the internal versus the external pallidal segments) and the two striatonigral projections systems (to pars compacta versus pars reticulata). The findings for GAD and the two neuropeptides were similar--the striatal projection to the external pallidal segment was the most vulnerable, showing substantial loss by grade 1. Loss of fibers in both subdivisions of the substantia nigra was also already great by grade 1. By contrast, the loss in the striatal projection system to the internal segment of globus pallidus proceeded more gradually. By grade 4 of HD, however, profound loss in all projection systems was apparent. These findings support the notion that the striatal neurons preferentially projecting to the internal pallidal segment are, in fact, less vulnerable in HD than are the other striatal projection neuron types.

Anandamide hydrolysis: a new target for anti-anxiety drugs?

The major psychoactive constituent of cannabis, Delta(9)-tetrahydrocannabinol, affects emotional states in humans and laboratory animals by activating brain cannabinoid receptors. A primary endogenous ligand of these receptors is anandamide, the amide of arachidonic acid with ethanolamine. Anandamide is released in selected regions of the brain and is deactivated through a two-step process consisting of transport into cells followed by intracellular hydrolysis. Pharmacological blockade of the enzyme fatty acid amide hydrolase (FAAH), which is responsible for intracellular anandamide degradation, produces anxiolytic-like effects in rats without causing the wide spectrum of behavioral responses typical of direct-acting cannabinoid agonists. These findings suggest that anandamide contributes to the regulation of emotion and anxiety, and that FAAH might be the target for a novel class of anxiolytic drugs.

Cannabinoid receptor agonists inhibit sensory nerve activation in guinea pig airways

We examined the effects of cannabinoid receptor agonists on various respiratory reactions induced by the activation of capsaicin-sensitive afferent sensory nerves (C-fibers). (R)-(+)-[2,3-dihydro-5-methyl-3-[(4-merpholino)methyl]pyrrolo-[1,2,3-de]-1,4-benzoxazin-6-yl](1-naphthyl)methanone (WIN 55212-2) dose-dependently inhibited electrical field stimulation- and capsaicin-induced guinea pig bronchial smooth muscle contraction, but not the neurokinin A-induced contraction. A cannabinoid CB2 receptor antagonist, [N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)pyrazole-3-carboxamide] (SR 144528), reduced the inhibitory effect of WIN 55212-2, but not a cannabinoid CB1 antagonist, [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamidehydrochloride] (SR 141716A). A cannabinoid CB2 agonist, JWH 133, also inhibited electrical field stimulation-induced guinea pig bronchial smooth muscle contraction and its inhibitory effect was blocked by SR 144528. The inhibitory effect of WIN 55212-2 on electrical field stimulation-induced bronchial contraction was reduced by the pretreatment of large conductance Ca(2+)-activated K+ channel (Maxi-K+ channel) blockers, iberiotoxin and charybdotoxin, but not other K+ channel blockers, dendrotoxin or glibenclamide. A Maxi-K+ channel opener, 1-(2'-hydroxy-5'-trifluoromethylphenyl)-5-trifluoromethyl-2(3H)benzimidazolone (NS1619), inhibited bronchial contraction induced by electrical field stimulation. WIN 55212-2 and JWH 133 blocked the capsaicin-induced release of substance P-like immunoreactivity from guinea pig airway tissues. These findings suggest that WIN 55212-2 inhibit the activation of C-fibers via cannabinoid CB2 receptors and Maxi-K+ channels in guinea pig airways.

The psychotomimetic effects of intravenous delta-9-tetrahydrocannabinol in healthy individuals: implications for psychosis

Recent advances in the understanding of brain cannabinoid receptor function have renewed interest in the association between cannabinoid compounds and psychosis. In a 3-day, double-blind, randomized, and counterbalanced study, the behavioral, cognitive, and endocrine effects of 0, 2.5, and 5 mg intravenous delta-9-tetrahydrocannabinol (Delta-9-THC) were characterized in 22 healthy individuals, who had been exposed to cannabis but had never been diagnosed with a cannabis abuse disorder. Prospective safety data at 1, 3, and 6 months poststudy was also collected. Delta-9-THC (1) produced schizophrenia-like positive and negative symptoms; (2) altered perception; (3) increased anxiety; (4) produced euphoria; (5) disrupted immediate and delayed word recall, sparing recognition recall; (6) impaired performance on tests of distractibility, verbal fluency, and working memory (7) did not impair orientation; (8) increased plasma cortisol. These data indicate that Delta-9-THC produces a broad range of transient symptoms, behaviors, and cognitive deficits in healthy individuals that resemble some aspects of endogenous psychoses. These data warrant further study of whether brain cannabinoid receptor function contributes to the pathophysiology of psychotic disorders.

Cannabis improves night vision: a case study of dark adaptometry and scotopic sensitivity in kif smokers of the Rif mountains of northern Morocco

Previous reports have documented an improvement in night vision among Jamaican fishermen after ingestion of a crude tincture of herbal cannabis, while two members of this group noted that Moroccan fishermen and mountain dwellers observe an analogous improvement after smoking kif, sifted Cannabis sativa mixed with tobacco (Nicotiana rustica). Field-testing of night vision has become possible with a portable device, the LKC Technologies Scotopic Sensitivity Tester-1 (SST-1). This study examines the results of double-blinded graduated THC administration 0-20 mg (as Marinol) versus placebo in one subject on measures of dark adaptometry and scotopic sensitivity. Analogous field studies were performed in Morocco with the SST-1 in three subjects before and after smoking kif. In both test situations, improvements in night vision measures were noted after THC or cannabis. It is believed that this effect is dose-dependent and cannabinoid-mediated at the retinal level. Further testing may assess possible clinical application of these results in retinitis pigmentosa or other conditions.

Effects of prenatal marijuana on response inhibition: an fMRI study of young adults

The neurophysiological effects of prenatal marijuana exposure on response inhibition were assessed in 18- to 22-year-olds. Thirty-one participants from the Ottawa Prenatal Prospective Study (OPPS) performed a blocked design Go/No-Go task while neural activity was imaged with functional magnetic resonance imaging (fMRI). The OPPS is a longitudinal study that provides a unique body of information collected from each participant over 20 years, including prenatal drug history, detailed cognitive/behavioral performance from infancy to young adulthood, and current and past drug usage. The fMRI results showed that with increased prenatal marijuana exposure, there was a significant increase in neural activity in bilateral prefrontal cortex and right premotor cortex during response inhibition. There was also an attenuation of activity in left cerebellum with increased prenatal exposure to marijuana when challenging the response inhibition neural circuitry. Prenatally exposed offspring had significantly more commission errors than nonexposed participants, but all participants were able to perform the task with more than 85% accuracy. These findings were observed when controlling for present marijuana use and prenatal exposure to nicotine, alcohol and caffeine, and suggest that prenatal marijuana exposure is related to changes in neural activity during response inhibition that last into young adulthood.

Central effects of the cannabinoid receptor agonist WIN55212-2 on respiratory and cardiovascular regulation in anaesthetised rats

1 The primary aim was to study the central respiratory effects of cannabinoids (CB). To this end, the cannabinoid receptor agonist WIN55212-2 was injected into the cisterna magna of urethane-anaesthetised rats and changes in respiratory parameters were observed. The secondary aim was to observe the centrally elicited cardiovascular actions of WIN55212-2. Involvement of opioid mechanisms in the central effects of WIN55212-2 was also studied. 2 Intracisternal (i.c.) application of WIN55212-2 (1, 3, 10 and 30 microg kg(-1)) dose-dependently decreased the respiratory rate and minute volume. Tidal volume was slightly increased, whereas peak inspiratory flow remained unchanged. In addition, WIN55212-2 increased mean arterial pressure and the plasma noradrenaline concentration and decreased heart rate. 3 I.c. injection of WIN55212-3 (1, 3, 10 and 30 microg kg(-1)), an enantiomer of WIN55212-2 lacking affinity for cannabinoid receptors, elicited no effects. All effects of WIN55212-2 were prevented by the CB1 receptor antagonist SR141716 (2 mg kg(-1) i.v.). I.c. administration of the opioid receptor agonist DAMGO (0.1, 0.3, 1 and 3 microg kg(-1)) markedly lowered the respiratory rate, tidal volume, minute volume and peak inspiratory flow. These effects were attenuated by the opioid receptor antagonist naloxone (0.2 mg kg(-1) i.v.). In contrast, naloxone did not affect the respiratory and cardiovascular effects of i.c. administered WIN55212-2. 4 Our results show that activation of CB1 cannabinoid receptors in the brain stem depresses respiration and enhances sympathetic tone and cardiac vagal tone. Opioid mechanisms are not involved in these central cannabinoid effects.

Cannabis-induced propriospinal myoclonus

We report on a case of a 25-year-old woman with clusters of myoclonus induced by a single exposure to inhaled cannabis. Investigations excluded a structural abnormality of the spine. Multi-channel surface EMG with parallel frontal EEG recording confirmed the diagnosis of propriospinal myoclonus.

[123I]AM281 single-photon emission computed tomography imaging of central cannabinoid CB1 receptors before and after Delta9-tetrahydrocannabinol therapy and whole-body scanning for assessment of radiation dose in tourette patients

BACKGROUND

The cannabinoid CB1 receptor agonist Delta9-THC has been suggested for treatment of Tourette syndrome (TS). Based on animal studies, the CB1 antagonist [123I]AM281 (N-(Morpholin-4-yl)-1-(2,4-dichlorophenyl)-5-(4-[123I]iodophenyl)-4-methyl-1H-pyrazole-3-carboxamide) has been proposed for single photon emission computed tomography (SPECT) in humans. Our aims were to 1) evaluate specific binding of [123I]AM281 to CB1 receptors in TS patients and 2) assess radiation exposure associated with the use of AM281 labeled with 123I for SPECT and 124I for positron emission tomography.

METHODS

We employed [123I]AM281 in six TS patients before and after Delta9-THC treatment. Dynamic SPECT, plasma measurements (including metabolite analysis with thin layer chromatography), and whole-body imaging were performed. Regions of interest derived from magnetic resonance images were used to extract from SPECT uptake in an area with high CB1 density (lentiform nuclei) and reference regions. Specific over nonspecific partition coefficients V3" were calculated. Whole-body images were carried out for dosimetric analysis. Data obtained with [123I]AM281 were used to predict doses from [124I]AM281.

RESULTS

Mean V3" ranged from .19 to .31 and did not change significantly after Delta9-THC treatment. Nevertheless, in the only patient with a marked clinical response, V3" clearly declined. Thin layer chromatography revealed biexponential kinetics of tracer metabolism; about 60% remained nonmetabolized after 3 hours. Effective doses of .011 mSv/MBq for [123I]AM281 and .34 for [124I]AM281 were computed.

CONCLUSIONS

This study suggests that specific binding of [123I]AM281 to CB1 receptors can be detected in patients using SPECT. Radiation exposure with [123I]AM281 is low; that with [124I]AM281 is higher but acceptable for single investigations.

Synthesis of [O-methyl-11C]1-(2-chlorophenyl)-5-(4-methoxyphenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide: a potential PET ligand for CB1 receptors

Synthesis and in vitro evaluation of [O-methyl-(11)C]1-(2-chlorophenyl)-5-(4-methoxyphenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide ([(11)C]-1), a potential imaging agent for CB(1) receptors using PET is described. 1-(2-Chlorophenyl)-5-(4-hydroxyphenyl)-4-methyl-1H-pyrazole-3-carboxylic acid piperidin-1-ylamide (5), the precursor for radiolabeling, was synthesized from 4-OTBDPS-propiophenone (2) in five steps with 30% overall yield. The reaction of alcohol 5 with [(11)C]MeOTf at 60 degrees C afforded [(11)C]-1 with an average radiochemical yield of 14.5% (EOS) and >2000 Ci/mmol specific activity. The radiotracer was found to selectively label CB(1) receptors in slide-mounted sections of postmortem human brain containing prefrontal cortex as demonstrated by in vitro autoradiography using phosphor imaging.

Lymphocytes as a neural probe: potential for studying psychiatric disorders

There is an increasing body evidence pointing to a close integration between the central nervous system (CNS) and immunological functions with lymphocytes playing therein a central role. The authors provide arguments to consider blood lymphocytes as a convenient probe of--an albeit--limited number of cellular functions, including gene expression. The use of brain biopsies of living patients is unrealistic for biochemical investigation, therefore lymphocytes may be a convenient and accessible alternative. Numerous studies showed similarities between receptor expression and mechanisms of transduction processes of cells in the nervous system (e.g. neurons and glia) and lymphocytes. In several neuropsychiatric disorders, alteration of metabolism and cellular functions in the CNS, as well as disturbances in the main neurotransmitter and hormonal systems are concomitant with altered function and metabolism of blood lymphocytes. We summarize relevant investigations on depression, stress, Alzheimer's disease (AD) and schizophrenia. New techniques such as cDNA microarray gene expression and proteomics may give clues to define molecular abnormalities in psychiatric disorders and could eventually reveal information for diagnostic and treatment purposes. Taken together, these considerations suggest that lymphocyte could reflect the metabolism of brain cells, and may be exploited as a neural and possible genetic probe in studies of psychiatric disorders.

Phylogenomic and chemotaxonomic analysis of the endocannabinoid system

The endocannabinoid system consists of two cannabinoid (CB) receptors, seven ligands, and ligand-catabolizing enzymes such as fatty acid amid hydrolase (FAAH) and monoglyceride lipase (MGL). The system's phylogenetic distribution is poorly known. The ligands cannot be molecularly investigated because they are not polypeptides and their specific synthetic enzymes have not been identified, so no sequences are available. Ligand phylogenetics can be inferred, nonetheless, by their presence in a range of extant organisms. Thus a meta-analysis of ligand extraction studies was performed (chemotaxonomy), and compared to a molecular search for homologs of CB receptors, vanilloid receptors (VR1), FAAH, and MGL in the genomes of sequenced organisms (phylogenomics). Putative homologs underwent functional mapping to ascertain the presence of critical amino acid motifs known to impart protein functionality. From an evolutionary perspective it appears that (1) endocannabinoid ligands evolved before CB receptors; (2) the ligands evolved independently multiple times; (3) CB receptors evolved prior to the metazoan-bilaterian divergence (ie, between extant Hydra and leech), but were secondarily lost in the Ecdysozoa; (4) VR1 may predate CB receptors but its affinity for endocannabinoids is a recent acquisition, appearing after the lower vertebrate-mammal divergence; (5) MGL may be as old as the ligands, whereas FAAH evolved recently, after the appearance of vertebrates. FAAH's emergence correlates with VR1's newly-found affinity for anandamide; this overlap in evolutionary time is recapitulated by complementary distribution patterns of FAAH, VR1, and anandamide in the brain. Linking FAAH, VR1, and anandamide implies a coupling among the remaining "older" parts of the endocannabinoid system, MGL, CB receptors, and 2-AG.

Influence of age, postmortem delay and freezing storage period on cannabinoid receptor density and functionality in human brain

It has been suggested that cannabimimetic drugs could be of interest in the treatment of several nervous disorders. Thus, it is important to analyse the distribution and properties of cannabinoid (CB) receptors directly in human brain. As postmortem human tissue is subjected to the effects of several biological variables, we have analyzed by autoradiography the influence of age, postmortem delay and freezing storage period (at -25 degrees C) on two parameters corresponding to cannabinoid CB1 receptors in human frontal cortex: receptor density and degree of activation of G-proteins ([35S]GTPgammaS assays). A significant decrease in the amount of both receptor density and agonist-stimulated G-protein activity was observed with age, revealing a mean reduction of about 10% per decade. In contrast, no significant correlations were found with postmortem delay either for CB1 receptors density or functionality. Finally, both parameters (receptor density and [35S]GTPgammaS response) were significantly reduced with freezing storage period at -25 degrees C in frontal cortical layers. Non-linear analysis of these data yielded values between 12 and 24 months of storage for a 50% reduction. In conclusion, when studying CB1 receptor properties in human brain samples, a careful analysis (and matching) for variables such as age and freezing storage period has to be carried out.

Selective antagonist [3H]SR141716A binding to cannabinoid CB1 receptors is increased in the anterior cingulate cortex in schizophrenia

Previous studies suggest that long-term cannabis use causes cognitive impairment, including lack of motivation and impaired attention, conditions that also resemble core negative symptoms of schizophrenia. The anterior cingulate cortex (ACC) plays an important role in normal cognition, particularly in relation to motivation and attention. This could suggest that changes in the cannabinoid (CB) system might be present in the ACC of patients suffering schizophrenia. The present study examined the distribution and density of CB1 cannabinoid receptors in the left ACC taken postmortem from patients with schizophrenia (n=10) and matched control subjects (n=9). Radioligand binding of [3H]SR141716A, an antagonist that specifically targets CB1 receptors of the endogenous cannabinoid system, was examined on ACC sections using quantitative autoradiography. CB1 receptors had a homogeneous distribution among the layers of ACC. A significant 64% increase in [3H]SR141716A specific binding to CB1 receptors was found in the schizophrenia group as compared to the control group (mean+/-S.E.M.: 46.15+/-6.22 versus 28.02+/-4.20 fmol/mg estimated tissue equivalents; p=0.03). The present results support the suggestion that changes in the endogenous cannabinoid system in the ACC may be involved in the pathology of schizophrenia particularly in relation to negative symptoms.

Repeated, intermittent delta(9)-tetrahydrocannabinol administration to rats impairs acquisition and performance of a test of visuospatial divided attention

The residual neuropsychological effects of marijuana abuse in man indicate a dysfunction of the attentional/executive systems. Moreover, experimental investigations suggest that repeated, intermittent (subchronic) Delta(9)-tetrahydrocannabinol (THC), the main psychoactive ingredient of marijuana, alters neurotransmission in the frontal cortex of rats and humans, a key neural site mediating attention and executive functions. In the present studies, the acquisition and performance of a test of visuospatial attention (the lateralized reaction time task) after subchronic THC administration (10.0 mg/kg twice daily for 14 days) was examined. Rats previously administered THC showed impairments in this self-paced version of the classic multiple-choice serial reaction time task, which persisted 14 days after the final drug administration. Longer time points were not examined. These attentional impairments were transiently reversible with an acute amphetamine (0.5 mg/kg) challenge. These behavioral data demonstrate that chronic THC administration to rats induces an attentional deficit, similar to that observed in humans who abuse marijuana. Finally, amphetamine's ability to reverse the attentional impairments provides indirect evidence that monoaminergic deficits may be linked to the cognitive dysfunction.

Upregulation of CB1 receptors and agonist-stimulated [35S]GTPgammaS binding in the prefrontal cortex of depressed suicide victims

Endogenous and exogenous cannabinoids (CBs) acting through the CB(1) receptors have been implicated in the regulation of several behavioral and neuroendocrine functions. Modulation of endocannabinoidergic system by ethanol in mouse brain, and the association of suicide and mood disorders with alcoholism suggest possible involvement of the cannabinoidergic system in the pathophysiology of depression and suicide. Therefore, the present study was undertaken to examine the levels of CB(1) receptors and mediated signaling in the dorsolateral prefrontal cortex (DLPFC) of subjects with major depression who had died by suicides (depressed suicides, DS). [(3)H]CP-55,940 and CB(1) receptor-stimulated [(35)S]GTPgammaS binding sites were analyzed in membranes obtained from DLPFC of DS (10) and matched normal controls (10). Upregulation (24%, P<0.0001) of CB(1) receptor density (B(max)) was observed in DS (644.6+/-48.8 fmol/mg protein) compared with matched controls (493.3+/-52.7 fmol/mg protein). However, there was no significant alteration in the affinity of receptor (DS; 1.14+/-0.08 vs control; 1.12+/-0.10 nM). Higher density of CB(1) receptors in DS (38%, P<0.001) was also demonstrated by Western blot analysis. The CB(1) receptor-stimulated [(35)S]GTPgammaS binding was significantly greater (45%, P<0.001) in the DLPFC of DS compared with matched controls. The observed upregulation of CB(1) receptors with concomitant increase in the CB(1) receptor-mediated [(35)S]GTPgammaS binding suggests a role for enhanced cannabinoidergic signaling in the prefrontal cortex of DS. The cannabinoidergic system may be a novel therapeutic target in the treatment of depression and/or suicidal behavior.

Cannabis, cannabinoids and reproduction

In most countries Cannabis is the most widely used illegal drug. Its use during pregnancy in developed nations is estimated to be approximately 10%. Recent evidence suggests that the endogenous cannabinoid system, now consisting of two receptors and multiple endocannabinoid ligands, may also play an important role in the maintenance and regulation of early pregnancy and fertility. The purpose of this review is therefore twofold, to examine the impact that cannabis use may have on fertility and reproduction, and to review the potential role of the endocannabinoid system in hormonal regulation, embryo implantation and maintenance of pregnancy.

Cannabinoid CB2 receptors and fatty acid amide hydrolase are selectively overexpressed in neuritic plaque-associated glia in Alzheimer's disease brains

The endocannabinoid system is still poorly understood. Recently, the basic elements that constitute it, i.e., membrane receptors, endogenous ligands, and mechanisms for termination of the signaling process, have been partially characterized. There is a considerable lack of information, however, concerning the distribution, concentration, and function of those components in the human body, particularly during pathological events. We have studied the status of some of the components of the endocannabinoid system, fatty acid amide hydrolase and cannabinoid CB1 and CB2 receptors, in postmortem brains from patients with Alzheimer's disease. Using specific polyclonal antibodies, we have performed immunohistochemical analysis in hippocampus and entorhinal cortex sections from brains of Alzheimer's disease patients. Our results show that both fatty acid amide hydrolase and cannabinoid CB2 receptors are abundantly and selectively expressed in neuritic plaque-associated astrocytes and microglia, respectively, whereas the expression of CB1 receptors remains unchanged. In addition, the hydrolase activity seems to be elevated in the plaques and surrounding areas. Thus, some elements of the endocannabinoid system may be postulated as possible modulators of the inflammatory response associated with this neurodegenerative process and as possible targets for new therapeutic approaches.

Executive functioning in preschool-age children prenatally exposed to alcohol, cocaine, and marijuana

BACKGROUND

Reports from clinical and experimental (animal) research converge on the suggestion that prenatal exposure to alcohol, cocaine, or marijuana undermines executive functioning (EF) and its neurological underpinnings. However, large, adequately controlled, prospective studies of alcohol and marijuana effects on EF have reported conflicting findings, and there have been no such studies of cocaine exposure.

METHODS

EF was investigated in a cohort (n = 316) of 4-year-old children the majority of whose mothers had used varying combinations of cocaine, alcohol, and marijuana during pregnancy. With use of postpartum maternal report and biological assay, children were assigned to overlapping prenatal cocaine-exposed, alcohol-exposed, and marijuana-exposed groups and to complementary control groups. The postnatal environmental assessment included measures of maternal intellectual and psychosocial functioning, current drug or alcohol use, and home environment.

RESULTS

The children in the alcohol-exposed group had worse tapping-inhibition performance than children in the non-alcohol-exposed group, and this effect persisted when potential confounding environmental variables, other drug variables, and concurrent verbal intelligence were controlled for.

CONCLUSIONS

Prenatal alcohol is predictive of decreased EF in early childhood that could not be attributed to environmental factors. The results are discussed in terms of the age and overall high-risk status of the children.

The cannabinoid system: a role in both the homeostatic and hedonic control of eating?

Knowledge of the cannabinoid system and its components has expanded greatly over the past decade. There is increasing evidence for its role in the regulation of food intake and appetite. Cannabinoid system activity in the hypothalamus is thought to contribute to the homeostatic regulation of energy balance, under the control of the hormone leptin. A second component of cannabinoid-mediated food intake appears to involve reward pathways and the hedonic aspect of eating. With the cannabinoid system contributing to both regulatory pathways, it presents an attractive therapeutic target for the treatment of both obesity and eating disorders.

Chronic pubertal, but not adult chronic cannabinoid treatment impairs sensorimotor gating, recognition memory, and the performance in a progressive ratio task in adult rats

There is evidence from studies in humans and animals that a vulnerable period for chronic cannabinoid administration exists during certain phases of development. The present study tested the hypothesis that long-lasting interference of cannabinoids with the developing endogenous cannabinoid system during puberty causes persistent behavioral alterations in adult rats. Chronic treatment with the synthetic cannabinoid agonist WIN 55,212-2 (WIN) (1.2 mg/kg) or vehicle was extended over 25 days either throughout the rats' puberty or for a similar time period in adult rats. The rats received 20 injections intraperitoneally (i.p.), which were not delivered regularly. Adult rats were tested for object recognition memory, performance in a progressive ratio (PR) operant behavior task, locomotor activity, and prepulse inhibition (PPI) of the acoustic startle response (ASR). PPI was significantly disrupted only by chronic peripubertal cannabinoid treatment. This long-lasting PPI deficit was reversed by the acute administration of the dopamine antagonist haloperidol. Furthermore, we found deficits in recognition memory of pubertal-treated rats and these animals showed lower break points in a PR schedule, whereas food preference and locomotion were not affected. Adult chronic cannabinoid treatment had no effect on the behaviors tested. Therefore, we conclude that puberty in rats is a vulnerable period with respect to the adverse effects of cannabinoid treatment. Since PPI deficits, object recognition memory impairments, and anhedonia/avolition are among the endophenotypes of schizophrenia, we propose chronic cannabinoid administration during pubertal development as an animal model for some aspects of the etiology of schizophrenia.

Effects of levodopa on endocannabinoid levels in rat basal ganglia: implications for the treatment of levodopa-induced dyskinesias

The majority of Parkinson's disease patients undergoing levodopa therapy develop disabling motor complications (dyskinesias) within 10 years of treatment. Stimulation of cannabinoid receptors, the pharmacological target of Delta 9-tetrahydrocannabinol, is emerging as a promising therapy to alleviate levodopa-associated dyskinesias. However, the mechanisms underlying this beneficial action remain elusive, as do the effects exerted by levodopa therapy on the endocannabinoid system. Although levodopa is known to cause changes in CB1 receptor expression in animal models of Parkinson's disease, we have no information on whether this drug alters the brain concentrations of the endocannabinoids anandamide and 2-arachidonylglycerol. To address this question, we used an isotope dilution assay to measure endocannabinoid levels in the caudate-putamen, globus pallidus and substantia nigra of intact and unilaterally 6-OHDA-lesioned rats undergoing acute or chronic treatment with levodopa (50 mg/kg). In intact animals, systemic administration of levodopa increased anandamide concentrations throughout the basal ganglia via activation of dopamine D1/D2 receptors. In 6-OHDA-lesioned rats, anandamide levels were significantly reduced in the caudate-putamen ipsilateral to the lesion; however, neither acute nor chronic levodopa treatment affected endocannabinoid levels in these animals. In lesioned rats, chronic levodopa produced increasingly severe oro-lingual involuntary movements which were attenuated by the cannabinoid agonist R(+)-WIN55,212-2 (1 mg/kg). This effect was reversed by the CB1 receptor antagonist rimonabant (SR141716A). These results indicate that a deficiency in endocannabinoid transmission may contribute to levodopa-induced dyskinesias and that these complications may be alleviated by activation of CB1 receptors.

Preferential limbic expression of the cannabinoid receptor mRNA in the human fetal brain

The cannabinoid receptor one (CB1) is responsible for the effects of cannabis on motor and cognitive function in the CNS. There is to date very limited information about the CB1 gene expression in the human brain, in particular during fetal development. In the present study, in situ hybridization experiments were used to examine the microscopic and macroscopic organization of the CB1 mRNA expression in normal human fetal (approximately 20 weeks of development) and adult brains. The fetal brain showed a distinct heterogeneous pattern of the CB1 mRNA expression which was low to moderate in many brain areas. The most striking feature of the fetal brain was the intense expression in the hippocampal CA region and basal nuclear group of the amygdaloid complex. Many of the same brain areas that showed positive expression of the CB1 mRNA in the fetal brain also expressed the gene in the adult brain. However, aside from an intense expression in the hippocampus which resembled that in fetal brain, the adult brain showed very high expression throughout the cerebral cortex, caudate nucleus, putamen and cerebellar cortex. These results document a different pattern of the anatomical organization of the CB1 mRNA expression in the mid-gestation fetal and adult human brain. Overall, the high CB1 mRNA expression in the fetal hippocampus and amygdala indicates that these limbic structures might be most vulnerable to prenatal cannabis exposure.

Cannabinoid CB1 receptor protein expression in the rat hippocampus and entorhinal, perirhinal, postrhinal and temporal cortices: regional variations and age-related changes

Cannabinoids have been shown to disrupt memory processes and these effects occur primarily through cannabinoid CB1 receptors in the brain. The present study investigates, for the first time, the regional variations and age-related changes in CB1 protein expression in the hippocampus and its neighbouring entorhinal, perirhinal, postrhinal and temporal cortices using Western blotting. In young adult rats, CB1 protein was highly expressed in the hippocampus and within the hippocampus, the greatest density of CB1 protein was located in CA1. When a comparison was made between young (4-month-old) and aged (24-month-old) rats, CB1 protein expression was significantly increased in the aged entorhinal and temporal cortices and was significantly decreased in the aged postrhinal cortex. The present study demonstrates region-specific changes in CB1 protein expression during ageing and further suggests that cannabinoid CB1 receptors may contribute to the aging process.

Cannabinoid1 receptor in the dorsal vagal complex modulates lower oesophageal sphincter relaxation in ferrets

Delta9-tetrahydrocannabinol (delta9-THC) is an effective anti-emetic; however, other potential gastrointestinal therapeutic effects of delta9-THC are less well-known. Here, we report a role of delta9-THC in a vago-vagal reflex that can result in gastro-oesophageal reflux, that is, gastric distension-evoked lower oesophageal sphincter (LOS) relaxation. Oesophageal, LOS and gastric pressures were measured using a miniaturized, manometric assembly in decerebrate, unanaesthetized ferrets.Gastric distension (30 ml) evoked LOS relaxation (70 +/- 8% decrease from baseline). Delta9-THC administered systemically (0.2 mg kg-1, iv.) or directly to the dorsal hindbrain surface (0.002 mg),significantly attenuated the nadir of the gastric distention-evoked LOS relaxation, and time to reach maximal response. Similar increases to maximal effect were observed after treatment with the cannabinoid receptor agonist WIN 55,212-2 (0.2 mg kg-1 iv.). The effect of systemic delta9-THC on gastric distention-evoked LOS relaxation was reversed by a selective cannabinoid1 (CBI) receptor antagonist, SR141617A (1 mg kg-1 i.v.). Since this reflex is vagally mediated, we used a CB1 receptor antiserum and immunocytochemistry to determine its distribution in ferret vagal circuitry. CBI receptor staining was present in cell bodies within the area postrema, nucleus tractus solitarius (NTS) and nodose ganglion. Intense terminal-like staining was noted within the NTS and dorsal motor vagal nucleus (DMN). Neither nodose ganglionectomy nor vagotomy altered the CB1 receptor terminal-like staining in the dorsal vagal complex. Retrogradely labelled gastric- or LOS-projecting DMN neurones did not express CBI receptors within their soma. Therefore, CBI receptor staining in the NTS and DMN is not due to primary vagal afferents or preganglionic neurones. These novel findings suggest that delta9-THC can modulate reflex LOS function and that the most likely site of action is via the CBI receptor within the NTS. This effect of delta9-THC may have implications in treatment of gastro-oesophageal reflux and other upper gut disorders.

Role of endogenous cannabinoids in synaptic signaling

Research of cannabinoid actions was boosted in the 1990s by remarkable discoveries including identification of endogenous compounds with cannabimimetic activity (endocannabinoids) and the cloning of their molecular targets, the CB1 and CB2 receptors. Although the existence of an endogenous cannabinoid signaling system has been established for a decade, its physiological roles have just begun to unfold. In addition, the behavioral effects of exogenous cannabinoids such as delta-9-tetrahydrocannabinol, the major active compound of hashish and marijuana, await explanation at the cellular and network levels. Recent physiological, pharmacological, and high-resolution anatomical studies provided evidence that the major physiological effect of cannabinoids is the regulation of neurotransmitter release via activation of presynaptic CB1 receptors located on distinct types of axon terminals throughout the brain. Subsequent discoveries shed light on the functional consequences of this localization by demonstrating the involvement of endocannabinoids in retrograde signaling at GABAergic and glutamatergic synapses. In this review, we aim to synthesize recent progress in our understanding of the physiological roles of endocannabinoids in the brain. First, the synthetic pathways of endocannabinoids are discussed, along with the putative mechanisms of their release, uptake, and degradation. The fine-grain anatomical distribution of the neuronal cannabinoid receptor CB1 is described in most brain areas, emphasizing its general presynaptic localization and role in controlling neurotransmitter release. Finally, the possible functions of endocannabinoids as retrograde synaptic signal molecules are discussed in relation to synaptic plasticity and network activity patterns.

Sleep modulates cannabinoid receptor 1 expression in the pons of rats

Endocannabinoids seem to play a role in the modulation of alertness. Therefore, we measured cannabinoid receptor 1 (CB1R) protein by Western blot and messenger RNA (mRNA) by reverse transcription-polymerase chain reaction in the pons of rats across the 24-h period. We performed evaluations every 4 h beginning at 09:00 h. Rats were under a controlled light/dark cycle 12:12 (lights on at 08:00 h). Our data suggest that the expression of CB1R gene depends on diurnal variations, with maximum expression at 13:00 h for protein and 21:00 h for mRNA, and minimum expression at 01:00 and 09:00 h, respectively. We also analyzed CB1R protein and mRNA levels in the pons of rats deprived of total sleep for 24 h and in rats with a 24-h period of sleep deprivation plus a 2-h period of sleep rebound. Unlike sleep deprivation, sleep rebound significantly increased CB1R protein while decreasing mRNA. Despite the fact that we used gentle manipulation to deprive the animals of sleep, there may be a potential influence of stress on this effect, too. However, these facts suggest that CB1R gene expression is modulated by the light/dark cycle and by sleep.

Ontogenetic development of cannabinoid receptor expression and signal transduction functionality in the human brain

Previous evidence suggests that the endogenous cannabinoid system emerges relatively early during brain development in the rat. However, the pre- and postnatal pattern of appearance of CB1 cannabinoid receptors in humans has not been analysed in detail. Furthermore, there is a complete lack of information about the functional ability of these proteins to activate signal transduction mechanisms during human development. In the present study we have explored CB1 receptor expression throughout the different areas of the developing human brain by [3H]CP55 940 autoradiography. We have also assessed CB1 functional coupling to G proteins during brain development by agonist-stimulated [35S]GTPgammaS autoradiography in the same cases. Our results indicate a significant density of cannabinoid receptors at 19 weeks' gestation in the same areas that contain these receptors in the adult human brain. Autoradiographic levels of CB1 receptors in these structures seem to increase progressively from early prenatal stages to adulthood. Interestingly, high densities of cannabinoid receptors have also been detected during prenatal development in fibre-enriched areas that are practically devoid of them in the adult brain. In parallel with these data, we have found that brain cannabinoid receptors are functionally coupled to signal transduction mechanisms from early prenatal stages. This early pattern of expression of functionally active cannabinoid receptors, along with the transient and atypical localization of these proteins in white matter areas during the prenatal stages, suggest an specific role of the endocannabinoid system in the events related to human neural development.

The origin of brain asymmetry and its psychotic reversal

Ontogenetic brain-asymmetry and its reversal in schizophrenia constitute special cases of a more fundamental principle of sensory-motor integration. Transmitted through an immature optical system, asymmetric inputs from the left visual field induce the infant's right hemispheric preference for lower spatial frequencies during early mother-child interaction. The emerging classical features of hemispheric specialisation later in life can be accounted for by a transformation law of the neuronal reference frames based on relativistic non-linear information processing. Accordingly, the asymmetric distributions of the cannabinoid receptor CB1 in the right basal ganglia and the left area of Wernicke reflect the preferences for lateralised posture, positioning, and speech. Epigenetic development of brain asymmetry thus unifies the different aspects related to cradling and breast-feeding, speech- and visuospatial processing, the dimensional conversion of spatiotemporal information and, in the case of a dysbalanced cannabinoid system, its psychotic reversal. The predicted right hemispheric shift and the inverse relationship between Kolmogorov entropy and its dimensional embedding (Shannon entropy) has ultimately been confirmed by non-linear EEG analysis of a fluoro-methyl-anadamide induced model psychosis splitting conscious from unconscious mental processes.

Executive functioning in preschool-age children prenatally exposed to alcohol, cocaine, and marijuana

BACKGROUND

Reports from clinical and experimental (animal) research converge on the suggestion that prenatal exposure to alcohol, cocaine, or marijuana undermines executive functioning (EF) and its neurological underpinnings. However, large, adequately controlled, prospective studies of alcohol and marijuana effects on EF have reported conflicting findings, and there have been no such studies of cocaine exposure.

METHODS

EF was investigated in a cohort (n = 316) of 4-year-old children the majority of whose mothers had used varying combinations of cocaine, alcohol, and marijuana during pregnancy. With use of postpartum maternal report and biological assay, children were assigned to overlapping prenatal cocaine-exposed, alcohol-exposed, and marijuana-exposed groups and to complementary control groups. The postnatal environmental assessment included measures of maternal intellectual and psychosocial functioning, current drug or alcohol use, and home environment.

RESULTS

The children in the alcohol-exposed group had worse tapping-inhibition performance than children in the non-alcohol-exposed group, and this effect persisted when potential confounding environmental variables, other drug variables, and concurrent verbal intelligence were controlled for.

CONCLUSIONS

Prenatal alcohol is predictive of decreased EF in early childhood that could not be attributed to environmental factors. The results are discussed in terms of the age and overall high-risk status of the children.

Therapeutic potential of cannabinoids in CNS disease

The major psychoactive constituent of Cannabis sativa, delta(9)-tetrahydrocannabinol (delta(9)-THC), and endogenous cannabinoid ligands, such as anandamide, signal through G-protein-coupled cannabinoid receptors localised to regions of the brain associated with important neurological processes. Signalling is mostly inhibitory and suggests a role for cannabinoids as therapeutic agents in CNS disease where inhibition of neurotransmitter release would be beneficial. Anecdotal evidence suggests that patients with disorders such as multiple sclerosis smoke cannabis to relieve disease-related symptoms. Cannabinoids can alleviate tremor and spasticity in animal models of multiple sclerosis, and clinical trials of the use of these compounds for these symptoms are in progress. The cannabinoid nabilone is currently licensed for use as an antiemetic agent in chemotherapy-induced emesis. Evidence suggests that cannabinoids may prove useful in Parkinson's disease by inhibiting the excitotoxic neurotransmitter glutamate and counteracting oxidative damage to dopaminergic neurons. The inhibitory effect of cannabinoids on reactive oxygen species, glutamate and tumour necrosis factor suggests that they may be potent neuroprotective agents. Dexanabinol (HU-211), a synthetic cannabinoid, is currently being assessed in clinical trials for traumatic brain injury and stroke. Animal models of mechanical, thermal and noxious pain suggest that cannabinoids may be effective analgesics. Indeed, in clinical trials of postoperative and cancer pain and pain associated with spinal cord injury, cannabinoids have proven more effective than placebo but may be less effective than existing therapies. Dronabinol, a commercially available form of delta(9)-THC, has been used successfully for increasing appetite in patients with HIV wasting disease, and cannabinoid receptor antagonists may reduce obesity. Acute adverse effects following cannabis usage include sedation and anxiety. These effects are usually transient and may be less severe than those that occur with existing therapeutic agents. The use of nonpsychoactive cannabinoids such as cannabidiol and dexanabinol may allow the dissociation of unwanted psychoactive effects from potential therapeutic benefits. The existence of other cannabinoid receptors may provide novel therapeutic targets that are independent of CB(1) receptors (at which most currently available cannabinoids act) and the development of compounds that are not associated with CB(1) receptor-mediated adverse effects. Further understanding of the most appropriate route of delivery and the pharmacokinetics of agents that act via the endocannabinoid system may also reduce adverse effects and increase the efficacy of cannabinoid treatment. This review highlights recent advances in understanding of the endocannabinoid system and indicates CNS disorders that may benefit from the therapeutic effects of cannabinoid treatment. Where applicable, reference is made to ongoing clinical trials of cannabinoids to alleviate symptoms of these disorders.

Endogenous cannabinoid system as a modulator of food intake

The ability of Cannabis sativa (marijuana) to increase hunger has been noticed for centuries, although intensive research on its molecular mode of action started only after the characterization of its main psychoactive component Delta(9)-tetrahydrocannabinol in the late 1960s. Despite the public concern related to the abuse of marijuana and its derivatives, scientific studies have pointed to the therapeutic potentials of cannabinoid compounds and have highlighted their ability to stimulate appetite, especially for sweet and palatable food. Later, the discovery of specific receptors and their endogenous ligands (endocannabinoids) suggested the existence of an endogenous cannabinoid system, providing a physiological basis for biological effects induced by marijuana and other cannabinoids. Epidemiological reports describing the appetite-stimulating properties of cannabinoids and the recent insights into the molecular mechanisms underlying cannabinoid action have proposed a central role of the cannabinoid system in obesity. The aim of this review is to provide an extensive overview on the role of this neuromodulatory system in feeding behavior by summarizing the most relevant data obtained from human and animal studies and by elucidating the interactions of the cannabinoid system with the most important neuronal networks and metabolic pathways involved in the control of food intake. Finally, a critical evaluation of future potential therapeutical applications of cannabinoid antagonists in the therapy of obesity and eating disorders will be discussed.

Antiemetic and motor-depressive actions of CP55,940: cannabinoid CB1 receptor characterization, distribution, and G-protein activation

Dibenzopyran (Delta(9)-tetrahydrocannabinol) and aminoalkylindole [R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrolol[1,2,3-de]-1,4-benzoxazin-yl]-(1-naphthalenyl) methanone mesylate; (WIN55,212-2)] cannabinoids suppress vomiting produced by cisplatin via cannabinoid CB(1) receptors. This study investigates the antiemetic potential of the "nonclassical" cannabinoid CP55,940 [1alpha,2beta-(R)-5alpha]-(-)-5-(1,1-dimethyl)-2-[5-hydroxy-2-(3-hydroxypropyl) cyclohexyl-phenol] against cisplatin-induced vomiting and assesses the presence and functionality of cannabinoid CB(1) receptors in the least shrew (Cryptotis parva) brain. CP55,940 (0.025-0.3 mg/kg) reduced both the frequency of cisplatin-induced emesis (ID(50)=0.025 mg/kg) and the percentage of shrews vomiting (ID(50)=0.09 mg/kg). CP55,940 also suppressed shrew motor behaviors (ID(50)=0.06- 0.21 mg/kg) at such doses. The antiemetic and motor-suppressant actions of CP55,940 were countered by SR141716A [N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide], indicating both effects are cannabinoid CB(1) receptor-mediated. Autoradiographic studies with [3H]-SR141716A and [35S]-GTPgammaS binding revealed that the distribution of the cannabinoid CB(1) receptor and its activation pattern are similar to rodent brain and significant levels are present in brain loci (e.g., nucleus tractus solitarius (NTS)) that control emesis. The affinity rank order of structurally diverse cannabinoid ligands for cannabinoid CB(1) receptor in shrew brain is similar to rodent brain: HU-210=CP55,940=SR141716A>/=WIN55,212-2>/=delta-9-tetrahydrocannabinol>methanandamide=HU-211=cannabidiol=2-arachidonoylglycerol. This affinity order is also similar and is highly correlated to the cannabinoid EC(50) potency rank order for GTPgammaS stimulation except WIN55,212-2 and delta-9-tetrahydrocannabinol potency order were reversed. The affinity and the potency rank order of tested cannabinoids were significantly correlated with their antiemetic ID(50) potency order against cisplatin-induced vomiting (CP55,940>WIN55,212-2=delta-9-tetrahydrocannabinol) as well as emesis produced by 2-arachidonoylglycerol or SR141716A (CP55,940>WIN55,212-2>delta-9-tetrahydrocannabinol).

Modulation of anxiety through blockade of anandamide hydrolysis

The psychoactive constituent of cannabis, Delta(9)-tetrahydrocannabinol, produces in humans subjective responses mediated by CB1 cannabinoid receptors, indicating that endogenous cannabinoids may contribute to the control of emotion. But the variable effects of Delta(9)-tetrahydrocannabinol obscure the interpretation of these results and limit the therapeutic potential of direct cannabinoid agonists. An alternative approach may be to develop drugs that amplify the effects of endogenous cannabinoids by preventing their inactivation. Here we describe a class of potent, selective and systemically active inhibitors of fatty acid amide hydrolase, the enzyme responsible for the degradation of the endogenous cannabinoid anandamide. Like clinically used anti-anxiety drugs, in rats the inhibitors exhibit benzodiazepine-like properties in the elevated zero-maze test and suppress isolation-induced vocalizations. These effects are accompanied by augmented brain levels of anandamide and are prevented by CB1 receptor blockade. Our results indicate that anandamide participates in the modulation of emotional states and point to fatty acid amide hydrolase inhibition as an innovative approach to anti-anxiety therapy.

Cannabinoids inhibit striatonigral GABAergic neurotransmission in the mouse

The substantia nigra pars reticulata (SNR) belongs to the brain regions with the highest density of CB(1) cannabinoid receptors. Anatomical studies indicate that the great majority of CB(1) receptors in the SNR are localized on terminals of GABAergic axons arriving from the caudate-putamen (striatonigral axons). The aim of the present experiments was to clarify the role of CB(1) receptors on terminals of striatonigral axons. Oblique sagittal slices, including the caudate-putamen and the substantia nigra, were prepared from brains of young mice. Electrical stimulation in the caudate-putamen elicited GABAergic inhibitory postsynaptic currents (IPSCs) in the SNR, which were studied by patch-clamp techniques. The long latency of IPSCs (14+/-1 ms) suggests that striatonigral axons were indeed activated within the caudate-putamen. The synthetic CB(1)/CB(2) cannabinoid receptor agonist WIN55212-2 (R(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazin-yl]-(1-naphthalenyl)methanone mesylate; 10(-5) M) decreased the amplitude of IPSCs by 93+/-1%. CP55940 ((-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol; 10(-5) M), another CB(1)/CB(2) receptor agonist, also reduced IPSC amplitude, by 76+/-4%. The CB(1) cannabinoid receptor antagonist SR141716A (N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide; 10(-6) M) prevented the inhibition produced by WIN55212-2 (10(-5) M). Depolarization of SNR neurons led to suppression of IPSCs; this suppression was prevented by SR141716A (10(-6) M). Three observations indicate that the agonists inhibited neurotransmission presynaptically. (1) CP55940 (10(-5) M) enhanced the ratio of amplitudes of two IPSCs which were elicited by two electrical stimuli 100 ms apart (paired pulses). (2) WIN55212-2 (10(-5) M) did not change the amplitude of miniature IPSCs recorded in the presence of tetrodotoxin. (3) WIN55212-2 (10(-5) M) also had no effect on currents elicited in SNR neurons by ejection of the GABA(A) receptor agonist muscimol from a pipet. In summary, we have established a method which allows selective examination of GABAergic neurotransmission between striatonigral axons and SNR neurons. Using this method, the function of CB(1) cannabinoid receptors on terminals of striatonigral axons was unequivocally clarified. Activation of these receptors causes strong presynaptic inhibition of GABAergic neurotransmission between striatonigral axons and SNR neurons. This effect may be one explanation of the catalepsy observed in animals after cannabinoid administration. Endocannabinoids released from SNR neurons can modulate striatonigral neurotransmission by inhibiting GABA release from terminals of striatonigral axons.

Seasonal correlation of sporadic schizophrenia to Ixodes ticks and Lyme borreliosis

BACKGROUND: Being born in winter and spring is considered one of the most robust epidemiological risk factors for schizophrenia. The aetiology and exact timing of this birth excess, however, has remained elusive so far. Since during phylogeny, Borrelia DNA has led to multiple germ-line mutations within the CB1 candidate gene for schizophrenia, a meta analysis has been performed of all papers on schizophrenic birth excesses with no less than 3000 cases each. All published numerical data were then plotted against the seasonal distributions of Ixodes ticks worldwide. RESULTS: In the United States, Europe and Japan the birth excesses of those individuals who later in life develop schizophrenia mirror the seasonal distribution of Ixodes ticks nine months earlier at the time of conception. South of the Wallace Line, which limits the spread of Ixodes ticks and Borrelia burgdorferi into Australia, seasonal trends are less significant, and in Singapore, being non-endemic for Ixodes ticks and Lyme disease, schizophrenic birth excesses are absent. CONCLUSION: At present, it cannot be excluded that prenatal infection by B. burgdorferi is harmful to the implanting human blastocyst. The epidemiological clustering of sporadic schizophrenia by season and locality rather emphasises the risk to the unborn of developing a congenital, yet preventable brain disorder later in life.

Down-regulation of cannabinoid-1 (CB-1) receptors in specific extrahypothalamic regions of rats with dietary obesity: a role for endogenous cannabinoids in driving appetite for palatable food?

Agonists at cannabinoid-1 (CB-1) receptors stimulate feeding and particularly enhance the reward aspects of eating. To investigate whether endogenous cannabinoids might influence appetite for palatable food, we compared CB-1 receptor density in the forebrain and hypothalamus, between rats fed standard chow (n=8) and others given palatable food (n=8) for 10 weeks to induce dietary obesity. CB-1 receptor density was significantly decreased by 30-50% (P<0.05) in the hippocampus, cortex, nucleus accumbens and entopeduncular nucleus of diet-fed rats. Furthermore, CB-1 receptor density in the hippocampus, nucleus accumbens and entopeduncular nucleus was significantly inversely correlated with intake of palatable food (r(2)=0.25-0.35; all P<0.05). By contrast, CB-1 receptor binding in the hypothalamus was low and not altered in diet-fed rats. CB-1 receptor down-regulation is consistent with increased activation of these receptors by endogenous cannabinoids. Acting in areas such as the nucleus accumbens and hippocampus, which are involved in the hedonic aspects of eating, cannabinoids may therefore drive appetite for palatable food and thus determine total energy intake and the severity of diet-induced obesity. However, cannabinoids in the hypothalamus do not appear to influence this aspect of eating behaviour.

Topical cannabinoid agonist, WIN55,212-2, reduces cornea-evoked trigeminal brainstem activity in the rat

Cannabinoids act at receptors on peripheral and central neurons to modulate diverse physiological functions and produce analgesia. Corneal sensory nerves express the CB1 cannabinoid receptor and project to two spatially discrete regions of the lower brainstem, the trigeminal interpolaris/caudalis (Vi/Vc) transition and subnucleus caudalis/upper cervical cord (Vc/C1) junction region. The function of CB1 expression on corneal nerves is not known. To determine if cannabinoid receptors in the anterior eye affect the activity of trigeminal brainstem neurons at the Vi/Vc and Vc/C1 the CB1 agonist, WIN55,212-2 (WIN-2), was applied topically prior to chemical excitation of corneal afferent fibers. In the first series of experiments WIN-2 was applied topically prior to excitation of corneal nociceptors by mustard oil (MO). WIN-2 reduced significantly the number of Fos-like immunoreactive neuronal nuclei (Fos-LI) at the Vi/Vc transition (-46.7+/-8.2%, P<0.05), while smaller non-significant reductions occurred at the Vc/C1 junction region (-20.3+/-7.6%). The selective CB1 antagonist, SR141716A (1mg/kg, i.v.), prevented WIN-2-evoked reduction in Fos-LI after MO. Systemic administration of WIN-2 (1 or 10mg/kg, i.p.) or SR141716A (1mg/kg, i.v.) or topical corneal application of morphine sulfate did not affect Fos-LI produced by MO. In parallel experiments, topical WIN-2 reduced the magnitude of single unit activity recorded at the Vi/Vc transition (-80+/-7%, P<0.025), but not at the Vc/C1 junction region (-34+/-30%) evoked by CO(2) pulses applied to the cornea. Topical morphine did not alter CO(2)-evoked unit activity at either recording location. These results indicated that cannabinoid receptor agonists acted, at least in part, at CB1 receptors in the anterior eye to reduce corneal stimulation-evoked trigeminal brainstem neural activity. Corneal nociceptor-evoked activity at the Vi/Vc transition was reduced significantly by topical WIN-2, while activity at the Vc/C1 junction region displayed only minor decreases. These findings were consistent with the hypothesis that CB1 receptors affect the activity of corneal-responsive neurons that preferentially contribute to homeostasis of the anterior eye and/or reflexive aspects of nociception rather than the sensory-discriminative aspects of corneal nociception.

Cellular localization of cannabinoid receptors and activated G-proteins in rat anterior cingulate cortex

Cannabinoid receptors are found in moderate density throughout the cerebral cortex. The anterior cingulate cortex (ACC) is of particular interest due its high level of cannabinoid receptors and role in behaviors known to be modulated by cannabinoids. These studies were conducted to determine the cellular localization of cannabinoid receptors and to compare the level of cannabinoid receptor binding with receptor-mediated G-protein activity in the rat ACC. Either ibotenic acid or undercut lesions were made in ACC, and brains were processed for [3H]WIN 55,212-2 and WIN 55,212-2-stimulated [35S]GTPgammaS autoradiography. Both cannabinoid receptors and receptor-activated G-proteins were highest in laminae I and VI of ACC in control tissue. Although similar levels of receptor binding were found in these laminae, significantly higher levels of receptor-activated G-proteins were found in lamina VI. Ibotenic acid lesions that destroyed ACC neurons decreased [3H]WIN 55,212-2 binding by 60-70% and eliminated WIN 55,212-2-stimulated [35S]GTPgammaS binding. In contrast, deafferentation of the ACC with undercut lesions had no significant effect on cannabinoid receptor binding or G-protein activation. These results indicate that cannabinoid receptors in laminae I and VI of the ACC are located on somatodendritic elements or axons intrinsic to the ACC. In addition, differences in the relative levels of cannabinoid binding sites and activated G-proteins between cortical laminae indicate that the efficiency of cannabinoid receptors for G-protein activation may vary within a specific brain region.