Drugs of abuse and immediate-early genes in the forebrain

A diverse array of chemical agents have been self administered by humans to alter the psychological state. Such drugs of abuse include both stimulants and depressants of the central nervous system. However, some commonalties must underlie the neurobiological actions of these drugs, since the desire to take the drugs often crosses from one drug to another. Studies have emphasized a role of the ventral striatum, especially the nucleus accumbens, in the actions of all drugs of abuse, although more recent studies have implicated larger regions of the forebrain. Induction of immediate-early genes has been studied extensively as a marker for activation of neurons in the central nervous system. In this review, we survey the literature reporting activation of immediate-early gene expression in the forebrain, in response to administration of drugs of abuse. All drugs of abuse activate immediate-early gene expression in the striatum, although each drug induces a particular neuroanatomical signature of activation. Most drugs of abuse activate immediate-early gene expression in several additional forebrain regions, including portions of the extended amygdala, cerebral cortex, lateral septum, and midline/intralaminar thalamic nuclei, although regional variations are found depending on the particular drug administered. Common neuropharmacological mechanisms responsible for activation of immediate-early gene expression in the forebrain involve dopaminergic and glutamatergic systems. Speculations on the biological significance and clinical relevance of immediate-early gene expression in response to drugs of abuse are presented.     

A Structural Insight into the Molecular Recognition of a (−)-Δ-Tetrahydrocannabinol and the Development of a Sensitive, One-Step, Homogeneous Immunocomplex-Based Assay for Its Detection

(−)-Δ⁹-Tetrahydrocannabinol (THC) is the main psychoactive compound found in cannabis. In this study, an anti-THC Fab fragment, designed T3, was isolated from a display library cloned from the spleen cells of a mouse immunized with a THC-bovine serum albumin conjugate, and the crystal structures of the T3 Fab in its free form and in complex with THC were determined at 1.9 Å and 2.0 Å resolution, respectively. The THC binding site of the T3 Fab is a narrow cavity: the n-pentyl group of THC protrudes deep into the interface area between the variable domains and the C₁₀ monoterpene moiety of the hapten is partially exposed to solvent. The metabolites of THC, with modifications in the C₁₀ monoterpene moiety, 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol and 11-hydroxy-Δ⁹-tetrahydrocannabinol, are bound by the T3 Fab with a higher affinity than THC. The crystal structures suggest that Ser52H and Arg53H of the T3 Fab are able to make hydrogen bonds with the metabolites, which leads to an increased binding against these metabolites. By developing a T3 Fab-Δ⁹-THC immunocomplex binding antibody from a naïve antibody phage display library, the specificity of the Δ⁹-THC binding is highly increased, which allows a one-step, homogeneous, fluorescence resonance energy transfer-based sensitive immunoassay, with a detection limit of 20 ng/ml from saliva samples.     

大麻植物中大麻素成分研究进展

大麻（Cannabis sativa）是一种古老的栽培植物, 它既是一种毒品原植物, 又是一种极具开发利用价值的经济作物。大麻素是大麻植物中特有的含有烷基和单萜分子结构的一类次生代谢产物, 目前已分离出70多种, 其中包含使人致幻成瘾的四氢大麻酚（THC）。该文就大麻植物中几种主要的大麻素成分： 四氢大麻酚、大麻二酚（CBD）和大麻环萜酚（CBC）的存在特征、含量变化、生物合成途径、各关键酶及其基因、遗传方式等方面的研究进行概括和归纳, 并展望了当前大麻素的主要研究方向, 对加快我国大麻素的相关研究及大麻育种具有参考意义。     

Activation of brain prostanoid EP3 receptors via arachidonic acid cascade during behavioral suppression induced by Delta8-tetrahydrocannabinol

We have previously shown that behavioral changes induced by cannabinoid were due to an elevation of prostaglandin E2 (PGE2) via the arachidonic acid cascade in the brain. In the present study, we investigated the participation of the prostanoid EP3 receptor, the target of PGE2 in the brain, in behavioral suppression induced by Delta8-tetrahydrocannabinol (Delta8-THC), an isomer of the naturally occurring Delta9-THC, using a one-lever operant task in rats. Intraperitoneal administration of Delta8-THC inhibited the lever-pressing behavior, which was significantly antagonized by both the selective cannabinoid CB1 receptor antagonist SR141716A and the cyclooxygenase inhibitor diclofenac. Furthermore, intracerebroventricular (i.c.v.) administration of PGE2 significantly inhibited the lever-pressing performance similar to Delta8-THC. Prostanoid EP3 receptor antisense-oligodeoxynucleotide (AS-ODN; twice a day for 3 days, i.c.v.) significantly decreased prostanoid EP3 receptor mRNA levels as determined by the RT-PCR analysis in the cerebral cortex, hippocampus and midbrain. AS-ODN also antagonized the PGE2-induced suppression of the lever pressing. In the same way, the suppression of lever-pressing behavior by Delta8-THC was significantly improved by AS-ODN. It is concluded that the suppression of lever-pressing behavior by cannabinoid is due to activation of the prostanoid EP3 receptor through an elevation of PGE2 in the brain.     

Immunochemical localization of tetrahydrocannabinol (THC) in cryofixed glandular trichomes of Cannabis (Cannabaceae)

Delta 9-tetrahydrocannabinol (THC) localization in glandular trichomes and bracteal tissues of Cannabis, prepared by high pressure cryofixation-cryosubstitution, was examined with a monoclonal antibody-colloidal gold probe by electron microscopy (EM). The antibody detected THC in the outer wall of disc cells during the presecretory cavity phase of gland development. Upon formation of the secretory cavity, the immunolabel detected THC in the disc cell wall facing the cavity as well as the subcuticular wall and cuticle throughout development of the secretory cavity. THC was detected in the fibrillar matrix associated with the disc cell and with this matrix in the secretory cavity. The antibody identified THC on the surface of secretory vesicles, but not in the secretory vesicles. Gold label also was localized in the anticlinal walls between adjacent disc cells and in the wall of dermal and mesophyll cells of the bract. Grains were absent or detected only occasionally in the cytoplasm of disc or other cells of the bract. No THC was detected in controls. These results indicate THC to be a natural product secreted particularly from disc cells and accumulated in the cell wall, the fibrillar matrix and surface feature of vesicles in the secretory cavity, the subcuticular wall, and the cuticle of glandular trichomes. THC, among other chemicals, accumulated in the cuticle may serve as a plant recognition signal to other organisms in the environment.     

Implication of Cannabinoids in Neurological Diseases

SUMMARY 1. Preparations from Cannabis sativa (marijuana) have been used for many centuries both medicinally and recreationally.2. Recent advances in the knowledge of its pharmacological and chemical properties in the organism, mainly due to Δ⁹-tetrahydrocannabinol, and the physiological roles played by the endocannabinoids have opened up new strategies in the treatment of neurological and psychiatric diseases.3. Potential therapeutic uses of cannabinoid receptor agonists include the management of spasticity and tremor in multiple sclerosis/spinal cord injury, pain, inflammatory disorders, glaucoma, bronchial asthma, cancer, and vasodilation that accompanies advanced cirrhosis. CB₁ receptor antagonists have therapeutic potential in Parkinson's disease.4. Dr. Julius Axelrod also contributed in studies on the neuroprotective actions of cannabinoids.     

Hippocampal Cannabinoid-1 Receptor Upregulation Upon Endothelin-B Receptor Deficiency: A Neuroprotective Substitution Effect?

Endothelin (ETB)-receptors mediate anti-apoptotic actions. Lack of functional ETB-receptors leads to increased neuronal apoptosis in the hippocampus. The increased apoptosis must be compensated by other mechanisms, however, as ETB-deficient rats display normal overall brain morphology. To illuminate on brain plasticity in ETB-receptor deficiency, we studied the expression and function of another neuroprotective system, the cannabinoid CB1-receptors, in ETB-deficient hippocampus. We show that CB1 expression in hippocampus increases postnatally in all rats but that the increase in CB1-receptor expression is significantly higher in ETB-deficient compared to wildtype littermates. Neuronal apoptosis decreases during brain maturation but remains on a significantly higher level in the ETB-deficient compared to wildtype dentate. When investigating survival of hippocampal neurons in culture, we found significant protection against hypoxia-induced cell death with CB1-analogs (noladin, (9-tetrahydrocannabinol) only in ETB-deficient neurons. We suggest that CB1-receptor upregulation in the ETB-mutant hippocampus reflects an attempt to compensate for the lack of ETB-receptors. Special issue dedicated to Dr. Bernd Hamprecht     

大麻种质资源中大麻素化学型及基因型鉴定与评价

大麻素(cannabinoids)是大麻植物中特有的次生代谢产物,主要成分为四氢大麻酚(THC,tetrahydrocannabinol)和大麻二酚(CBD,cannabidiol)。本研究通过对我国不同来源地的23份大麻种质资源共69个单株材料中THC和CBD含量特征及其合成关键酶基因多态性进行分析,鉴定了我国大麻种质资源的大麻素化学型及基因型。结果显示,69个单株中大麻素含量差异显著,THC含量均值为0.56%,范围为0.01%~2.45%;CBD含量均值为0.53%,范围为0~2.24%;根据CBD/THC含量比值,大麻资源可划分为毒品型(占44.93%)、中间型(占20.29%)和纤维型(占34.78%)3种大麻素化学型,毒品型、中间型中分别有93.5%和71.4%的植株中THC含量0.3%,纤维型植株中THC含量≤0.08%。3种化学型遗传位点(共显性位点B)的基因型分别为BT/BT、BT/BD和BD/BD;BT等位基因(THCAS)存在10个变异位点,氨基酸序列有4处变异,BD等位基因(CBDAS)存在4个变异位点,均为同义突变。根据THCAS和CBDAS基因多态性,设计了一个共显性复合PCR分子标记,可准确鉴定出大麻3种化学型。研究结果揭示了我国大麻种质资源中大麻素含量、化学型和基因型三者之间的关系,可为大麻素遗传研究与利用提供理论依据。