Cannabinoides Criam Neurônios!

[Canadense]

http://www.jci.org/articles/view/25509

Research Article Cannabinoids promote embryonic and adult hippocampus neurogenesis and produce anxiolytic- and antidepressant-like effects

Wen Jiang^1,2, Yun Zhang¹, Lan Xiao¹, Jamie Van Cleemput¹, Shao-Ping Ji¹, Guang Bai³ andXia Zhang¹

¹Neuropsychiatry Research Unit, Department of Psychiatry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
²Department of Neurology, Xijing Hospital, Fourth Military Medical University, Xi’an, People’s Republic of China.
³Department of Biomedical Sciences, Dental School, Program in Neuroscience, University of Maryland, Baltimore, Maryland, USA.

Address correspondence to: Xia Zhang, Neuropsychiatry Research Unit, 103 Wiggins Road, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E4. Phone: (306) 966-2288; Fax: (306) 966-8830; E-mail: zhangxia@duke.usask.ca.

First published October 1, 2005
Received for publication April 29, 2005, and accepted in revised form August 9, 2005.

The hippocampal dentate gyrus in the adult mammalian brain contains neural stem/progenitor cells (NS/PCs) capable of generating new neurons, i.e., neurogenesis. Most drugs of abuse examined to date decrease adult hippocampal neurogenesis, but the effects of cannabis (marijuana or cannabinoids) on hippocampal neurogenesis remain unknown. This study aimed at investigating the potential regulatory capacity of the potent synthetic cannabinoid HU210 on hippocampal neurogenesis and its possible correlation with behavioral change. We show that both embryonic and adult rat hippocampal NS/PCs are immunoreactive for CB1 cannabinoid receptors, indicating that cannabinoids could act on CB1 receptors to regulate neurogenesis. This hypothesis is supported by further findings that HU210 promotes proliferation, but not differentiation, of cultured embryonic hippocampal NS/PCs likely via a sequential activation of CB1 receptors, G_i/o proteins, and ERK signaling. Chronic, but not acute, HU210 treatment promoted neurogenesis in the hippocampal dentate gyrus of adult rats and exerted anxiolytic- and antidepressant-like effects. X-irradiation of the hippocampus blocked both the neurogenic and behavioral effects of chronic HU210 treatment, suggesting that chronic HU210 treatment produces anxiolytic- and antidepressant-like effects likely via promotion of hippocampal neurogenesis.

Introduction

Cannabis (marijuana, hashish, or cannabinoids) has been used for medical and recreational purposes for many centuries and is likely the only medicine or illicit drug that has constantly evoked tremendous interest or controversy within both the public domain and medical research. Cannabinoids appear to be able to modulate pain, nausea, vomiting, epilepsy, ischemic stroke, cerebral trauma, multiple sclerosis, tumors, and other disorders in humans and/or animals (1–7). However, marijuana has been the most commonly used illicit drug in developed countries, producing acute memory impairment and dependence/withdrawal symptoms in chronic users and animal models (6, 8–10). Cannabis acts on 2 types of cannabinoid receptors, the CB1 and CB2 receptors, which are distributed mainly in the brain and immune system, respectively. In the brain, CB1 receptors are also targeted by endogenous cannabinoids (i.e., endocannabinoids) such as anandamide (AEA), 2-arachidonylglycerol, and arachidonylethanolamide (1, 6, 10,11).

The recent discovery that the hippocampus is able to generate new neurons (i.e., neurogenesis) throughout the lifespan of mammals, including humans, has changed the way we think about the mechanisms of psychiatric disorders (12) and drug addiction (13). The subgranular zone of the dentate gyrus (SGZ) in the adult brain contains neural stem/progenitor cells (NS/PCs) capable of producing thousands of new granule cells per day (14). We, and others, have shown that these newborn hippocampal neurons are functionally integrated into the existing neuroanatomical circuitry (15, 16) and are positively correlated with hippocampus-dependent learning and memory processes (17) and the developmental mechanisms of stress and mood disorders (12). Recent studies have further shown that chronic fluoxetine treatment produced antidepressant and anxiolytic effects (18, 19) and the anxiolytic effects are likely achieved by promoting hippocampal neurogenesis (18).

Chronic administration of the major drugs of abuse including opiates, alcohol, nicotine, and cocaine has been reported to suppress hippocampal neurogenesis in adult rats (20–23), suggesting a potential role of hippocampal neurogenesis in the initiation, maintenance, and treatment of drug addiction (13). The recent finding of prominently decreased hippocampal neurogenesis in CB1-knockout mice (24) suggests that CB1 receptor activation by endogenous, plant-derived, or synthetic cannabinoids may promote hippocampal neurogenesis. However, endogenous cannabinoids have been reported to inhibit adult hippocampal neurogenesis (25). Nevertheless, it is possible that exo- and endocannabinoids could differentially regulate hippocampal neurogenesis, as exo- and endocannabinoids act as full or partial agonists on CB1 receptors, respectively (11).

The goal of the present study was to test the hypothesis that the potent synthetic cannabinoid HU210 is able to promote hippocampal neurogenesis, leading to the anxiolytic and antidepressant effects of cannabinoids. We demonstrate here that both HU210 and the endocannabinoid AEA promote proliferation of embryonic hippocampal NS/PCs without significant effects on their differentiation, resulting in more newborn neurons. The effects of HU210 on adult hippocampal neurogenesis were quantified in freely moving rats and were correlated with behavioral testing. We show that 1 month after chronic HU210 treatment, rats display increased newborn neurons in the hippocampal dentate gyrus and significantly reduced measures of anxiety- and depression-like behavior. Thus, cannabinoids appear to be the only illicit drug whose capacity to produce increased hippocampal newborn neurons is positively correlated with its anxiolytic- and antidepressant-like effects.

Results

Expression of CB1 receptors in embryonic and adult hippocampal NS/PCs. In the mammalian brain, the CB1 receptor is one of the most abundant G protein–coupled receptors, accounting for most, if not all, of the centrally mediated effects of cannabinoids (5). We reasoned that if cannabinoids were able to regulate neurogenesis, the NS/PCs capable of producing new neural cells would contain CB1 receptors. We therefore employed CB1 antibody immunocytochemistry, Western blotting, and PCR to examine CB1 protein and gene expression in cultured NS/PCs isolated from the hippocampus of E17 rat embryos. About 95% of the total neurosphere cells labeled with Hoeschst stain were also labeled with both CB1 and nestin (a marker for NS/PCs) antibodies (Figure1A). Some Hoechst-labeled cells in the neurospheres exhibited the shape of glial cells, with small round nuclei, and were CB1 immunoreactive but without nestin staining (Figure 1A). The staining of CB1 antibody appears specific for 2 reasons. First, Western blots with the same antibody and cultured NS/PC revealed a strong protein band with the molecular weight of 60 kDa (Figure 1 , which corresponds to the CB1 receptor (26). Second, we could not detect the positive immunostaining or 60-kDa protein band using the CB1 antibody preabsorbed with the antigen. Using PCR, we further identified a band of the predicted size (1,440 bp) corresponding to the full encoding region of CB1 (Figure 1C), suggesting the presence of CB1 transcripts in NS/PCs. Similar results, i.e., CB1 protein and gene expression, were seen in both second and sixth passages of NS/PCs. We then examined adult naive rats sacrificed 2 hours after receiving a single dose of BrdU to label dividing cells. We found that about 90% of BrdU-stained cells in the SGZ were also doubly labeled with CB1 (Figure 1D; n = 3). These results suggest that both embryonic and adult hippocampal NS/PCs express CB1 receptors.

Figure 1

Expression of CB1 receptors in NS/PCs. (A) Coimmunofluorescent staining of CB1 and nestin in cultured hippocampal NS/PCs derived from E17 embryos. Hoechst staining was conducted to reveal the total cultured cells. The arrow indicates the glial-like cells, located in the center of a neurosphere, with CB1 staining and without nestin staining. Scale bar, 20 μm. (B) Western blot using cultured NS/PC reveals a 60-kDa protein band corresponding to CB1 receptor. (C) PCR indicates CB1 gene expression in NS/PCs (lane 2) using primers yielding a predicted product of 1,440 bp (i.e., the full encoding region of CB1 receptor) from embryonic NS/PCs. Lane 1: molecular weight standards; lane 2: CB1 receptor; lane 3: PCR reaction without sample added. (D) Confocal microscopic assessments of costaining of BrdU and CB1 receptors in the SGZ located between the hilus and the granule cell layer (granule) of the dentate gyrus in an adult rat. Scale bar, 10 μm.

Increased proliferation of embryonic NS/PCs by HU210 and AEA. To examine the effects of HU210 on NS/PC proliferation, cultured embryonic NS/PCs were incubated with different concentrations of HU210. With the WST-8 assay, changes in NS/PC proliferation between HU210- and vehicle-treated culture were significant at some concentrations of HU210, as evidenced by significant group effects with 1-way ANOVA (F_5,18 = 513.129, P < 0.01). Specifically, when 10 nM to 1 μM of HU210 were added to the culture medium containing the mitogenic growth factors bFGF and EGF, the WST-8 assay showed a significant increase in NS/PC proliferation (Tukey post-hoc tests, P < 0.05); 1 nM of HU210 exerted no significant effects (P = 0.072); 10 μM produced profound toxic effects on cultured NS/PCs (Figure 2A). Because HU210 can activate both CB1 and CB2 receptors, we next used the selective CB1 receptor antagonist AM281 to identify the possible involvement of CB1 in the action of HU210 on NS/PC proliferation. Although 1 nM to 1 μM of AM281 alone produced no significant effects on NS/PC proliferation, 10 nM to 1 μM of AM281 blocked the promoting effects of 10 nM to 1 μM of HU210 on NS/PC proliferation (1-way ANOVA for repeated measures, F_2,25.713 = 16.792, P < 0.01; pairwise comparisons, HU210-treated cells with or without AM281: P < 0.01) (Figure 2A), suggesting that HU210 specifically acts on CB1 receptors to promote NS/PC proliferation. While 10 μM of AM281 alone significantly inhibited NS/PC proliferation (P < 0.01), this concentration of AM281 did not exert significant effects in preventing the lethal effects of 10 μM of HU210 on NS/PCs (Figure 2A), indicating that the lethal effects of 10 μM of HU210 on NS/PC cells were caused nonspecifically or by another receptor.

Figure 2

[playmogil]

porra.....

essa é da hora...

chora laranjas......

[Canadense]

o play, rola de fazer um merge com o outro???

[HST]

E fanatismo religioso atrofia o hipocampo cerebral.

http://www.scientificamerican.com/article/religious-experiences-shrink-part-of-brain/

Tá explicado.

[rentom]

Pode cre H... Maluco ler essas pesquisas sobre as capacidades do cerebro em equalizar e sintetizar substancias!

Ate vi outro dia um texto falando sobre a eutanasia e a extração do chromo como metodo medicinal para tratamento na dependencia, seja ela qal for, incluindo o fanatismo relegioso.

Fato ou mito... Ta pra nascer alguem que dixave esse rumo.

No mais, stress pode causar varios problemas como hipertensao que tb esta associado a diminuiçao da visao. Por oxidaçào... Ai o cacau entra como sugestao pra antioxidação...

Abraço ai!

[maninho123]

Obrigado pela informação Canadense! É sabido que a cannabis causa a neurogênese. Está na lista dos meus estudos para ler. Abração

[Fabrício BrasilC (olho)]

show demais heim? Invertendo completamente para alguns o senso pretensamente epistêmico (sabemos que mais ideológico) de que maconha "queima" neurônios.

Que loucura meu povo....por isso, gosto por demais de debater e aprender mais sobre C&T&I . Show o/ sinto que sou um jumento, uma mula perto da grandeza da cannabis . De fato, uma planta fantástica, por que não sagrada/medicinal/complexa. Nem todos merecem a cannabis.

A canábis não precisa do homem para nada. É justamente ao contrário, é o homem quem precisa da canábis para tudo.

obrigado pela info. fabrício.

[rentom]

É fabricio, tudo no corpo humano precisa ser estimulado e ter limites. Assim como tomar sol tem seus beneficios ou não... O uso do cerebro idem.