RESUMO
The prefrontal cortex (PFC) is a crucial hub for the flexible modulation of recent memories (executive functions) as well as for the stable organization of remote memories. Dopamine in the PFC is implicated in both these processes and genetic variants affecting its neurotransmission might control the unique balance between cognitive stability and flexibility present in each individual. Functional genetic variants in the catechol-O-methyltransferase (COMT) gene result in a different catabolism of dopamine in the PFC. However, despite the established role played by COMT genetic variation in executive functions, its impact on remote memory formation and recall is still poorly explored. Here we report that transgenic mice overexpressing the human COMT-Val gene (COMT-Val-tg) present exaggerated remote memories (>50 days) while having unaltered recent memories (<24 h). COMT selectively and reversibly modulated the recall of remote memories as silencing COMT Val overexpression starting from 30 days after the initial aversive conditioning normalized remote memories. COMT genetic overactivity produced a selective overdrive of the endocannabinoid system within the PFC, but not in the striatum and hippocampus, which was associated with enhanced remote memories. Indeed, acute pharmacological blockade of CB1 receptors was sufficient to rescue the altered remote memory recall in COMT-Val-tg mice and increased PFC dopamine levels. These results demonstrate that COMT genetic variations modulate the retrieval of remote memories through the dysregulation of the endocannabinoid system in the PFC.
Assuntos
Catecol O-Metiltransferase/metabolismo , Endocanabinoides/metabolismo , Memória de Longo Prazo/fisiologia , Córtex Pré-Frontal/metabolismo , Animais , Catecol O-Metiltransferase/genética , Cognição/fisiologia , Dopamina/metabolismo , Feminino , Genótipo , Humanos , Masculino , Memória/fisiologia , Camundongos , Camundongos Transgênicos , Polimorfismo GenéticoRESUMO
Marijuana is consistently the most widely used illicit drug among teenagers and most users first experiment it in adolescence. Adolescence is the period between childhood and adulthood, encompassing not only reproductive maturation, but also cognitive, emotional and social maturation and is characterized by a brain in transition that differs anatomically and neurochemically from that of the adult. The endocannabinoid system plays an important role in this critical phase for cerebral development, therefore a strong stimulation by the psychoactive component of marijuana, delta-9-tetrahydrocanabinol, that acts through the cannabinoid system, might lead to subtle but lasting neurobiological changes that can affect adult brain functions and behaviour. The literature here summarized, exploiting animal models of cannabis consumption, points to the presence of subtle changes in the adult brain circuits after heavy cannabis consumption in adolescence. These alterations lead to impaired emotional and cognitive performance, enhanced vulnerability for the use of more harmful drugs of abuse, and may represent a risk factor for developing schizophrenia in adulthood. The few studies examining the neurobiological basis of the altered behaviours demonstrate the presence of stable alteration in the endocannabinoid system that can trigger subsequent alteration in synaptic protein and synaptic morphology, thus altering the responsiveness of selected brain areas to different internal and external stimuli. These pre-clinical observations are strengthened by literature in humans where longitudinal studies often support the experimental results. There is an urgent need of multidisciplinary approaches combining behaviour with neurochemical and genetic studies to build a scientific based opinion on the long-lasting consequences of cannabis use in adolescence.
Assuntos
Comportamento/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Canabinoides/toxicidade , Transtornos Cognitivos/induzido quimicamente , Neurobiologia , Adolescente , Adulto , Encéfalo/fisiopatologia , Transtornos Cognitivos/fisiopatologia , Transtornos Cognitivos/psicologia , Humanos , Estudos LongitudinaisRESUMO
In the present study we explored with a multidisciplinary approach, the role of anandamide (AEA) in the modulation of anxiety behavior at the level of the prefrontal cortex (PFC). Low doses of the metabolically stable AEA analog, methanandamide, microinjected into the PFC, produced an anxiolytic-like response in rats, whereas higher doses induced anxiety-like behaviors. Pretreatment with the selective antagonist of CB1 or TRPV1 receptors (AM251 and capsazepine, respectively) suggested that the anxiolytic effect evoked by AEA might be due to the interaction with the CB1 cannabinoid receptor, whereas vanilloid receptors seem to be involved in AEA anxiogenic action. When AEA contents in the PFC were increased by microinjecting the selective inhibitor of fatty acid amide hydrolase (FAAH), URB597, we observed an anxiolytic response only at low doses of the compound and no effect or even an anxiogenic profile at higher doses. In line with this, a marked decrease of AEA levels in the PFC, achieved by lentivirus-mediated local overexpression of FAAH, produced an anxiogenic response. These findings support an anxiolytic role for physiological increases in AEA in the PFC, whereas more marked increases or decreases of this endocannabinoid might lead to an anxiogenic response due to TRPV1 stimulation or the lack of CB1 activation, respectively.
Assuntos
Ansiedade/fisiopatologia , Moduladores de Receptores de Canabinoides/fisiologia , Endocanabinoides , Córtex Pré-Frontal/fisiologia , Animais , Ansiedade/psicologia , Ácidos Araquidônicos/farmacologia , Benzamidas/farmacologia , Carbamatos/farmacologia , Relação Dose-Resposta a Droga , Masculino , Alcamidas Poli-Insaturadas/farmacologia , Córtex Pré-Frontal/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptor CB1 de Canabinoide/agonistas , Receptor CB1 de Canabinoide/antagonistas & inibidores , Receptor CB1 de Canabinoide/fisiologiaRESUMO
It has been recently reported that cannabidiol (CBD), a non-psychoactive cannabinoid, is able to kill glioma cells, both in vivo and in vitro, independently of cannabinoid receptor stimulation. However, the underlying biochemical mechanisms were not clarified. In the present study, we performed biochemical analysis of the effect of CBD both in vivo, by using glioma tumor tissues excised from nude mice, and in vitro, by using U87 glioma cells. In vivo exposure of tumor tissues to CBD significantly decreased the activity and content of 5-lipoxygenase (LOX, by approximately 40%), and of its end product leukotriene B4 ( approximately 25%). In contrast cyclooxygenase (COX)-2 activity and content, and the amount of its end product prostaglandin E2, were not affected by CBD. In addition, in vivo treatment with CBD markedly stimulated ( approximately 175%) the activity of fatty acid amide hydrolase (FAAH), the main anandamide-degrading enzyme, while decreasing anandamide content ( approximately 30%) and binding to CB1 cannabinoid receptors ( approximately 25%). In vitro pre-treatment of U87 glioma cells with MK-886, a specific 5-LOX inhibitor, significantly enhanced the antimitotic effect of CBD, whereas the pre-treatment with indomethacin (pan-COX inhibitor) or celecoxib (COX-2 inhibitor), did not alter CBD effect. The study of the endocannabinoid system revealed that CBD was able to induce a concentration-dependent increase of FAAH activity in U87 cells. Moreover, a significantly reduced growth rate was observed in FAAH-over-expressing U87 cells, compared to wild-type controls. In conclusion, the present investigation indicates that CBD exerts its antitumoral effects through modulation of the LOX pathway and of the endocannabinoid system, suggesting a possible interaction of these routes in the control of tumor growth.
Assuntos
Amidoidrolases/fisiologia , Antineoplásicos/metabolismo , Antineoplásicos/farmacologia , Araquidonato 5-Lipoxigenase/fisiologia , Canabidiol/metabolismo , Canabidiol/farmacologia , Animais , Canabinoides/metabolismo , Canabinoides/farmacologia , Linhagem Celular Tumoral , Relação Dose-Resposta a Droga , Feminino , Humanos , Camundongos , Camundongos Nus , Ensaios Antitumorais Modelo de Xenoenxerto/métodosRESUMO
There is a general consensus that the effects of cannabinoid agonists on anxiety seem to be biphasic, with low doses being anxiolytic and high doses ineffective or possibly anxiogenic. Besides the behavioural effects of cannabinoids on anxiety, very few papers have dealt with the neuroanatomical sites of these effects. We investigated the effect on rat anxiety behavior of local administration of THC in the prefrontal cortex, basolateral amygdala and ventral hippocampus, brain regions belonging to the emotional circuit and containing high levels of CB1 receptors. THC microinjected at low doses in the prefrontal cortex (10 microg) and ventral hippocampus (5 microg) induced in rats an anxiolytic-like response tested in the elevated plus-maze, whilst higher doses lost the anxiolytic effect and even seemed to switch into an anxiogenic profile. Low THC doses (1 microg) in the basolateral amygdala produced an anxiogenic-like response whereas higher doses were ineffective. All these effects were CB1-dependent and closely linked to modulation of CREB activation. Specifically, THC anxiolytic activity in the prefrontal cortex and ventral hippocampus was paralleled by an increase in CREB activation, whilst THC anxiogenic response in the basolateral amygdala was paralleled by a decrease in CREB activation. Our results suggest that while a mild activation of CB1 receptors in the prefrontal cortex and ventral hippocampus attenuates anxiety, a slight CB1 receptor stimulation in the amygdala results in an anxiogenic-like response. The molecular underpinnings of these effects involve a direct stimulation of CB1 receptors ending in pCREB modulation and/or a possible alteration in the fine tuning of local neuromodulator release.
Assuntos
Ansiedade/patologia , Ansiedade/fisiopatologia , Encéfalo/fisiopatologia , Receptor CB1 de Canabinoide/fisiologia , Tonsila do Cerebelo/efeitos dos fármacos , Analgésicos não Narcóticos , Análise de Variância , Animais , Ansiedade/tratamento farmacológico , Comportamento Animal/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Proteína de Ligação a CREB/metabolismo , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Dronabinol/uso terapêutico , Hipocampo/efeitos dos fármacos , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Microinjeções/métodos , Atividade Motora/efeitos dos fármacos , Piperidinas/farmacologia , Córtex Pré-Frontal/efeitos dos fármacos , Pirazóis/farmacologia , Ratos , Ratos Sprague-Dawley , Receptor CB1 de Canabinoide/efeitos dos fármacos , Fatores de TempoRESUMO
Despite the increasing use of cannabis among adolescents, there are little and often contradictory studies on the long-term neurobiological consequences of cannabis consumption in juveniles. Adolescence is a critical phase for cerebral development, where the endocannabinoid system plays an important role influencing the release and action of different neurotransmitters. Therefore, a strong stimulation by the psychoactive component of marijuana, delta-9-tetrahydrocanabinol (THC), might lead to subtle but lasting neurobiological changes that can affect adult brain functions and behaviour. The literature here summarized by use of experimental animal models, puts forward that heavy cannabis consumption in adolescence may induce subtle changes in the adult brain circuits ending in altered emotional and cognitive performance, enhanced vulnerability for the use of more harmful drugs of abuse in selected individuals, and may represent a risk factor for developing schizophrenia in adulthood. Therefore, the potential problems arising in relation to marijuana consumption in adolescence suggest that this developmental phase is a vulnerable period for persistent adverse effects of cannabinoids.
Assuntos
Comportamento/efeitos dos fármacos , Cannabis/efeitos adversos , Adolescente , Animais , Humanos , Modelos Biológicos , Transtornos Psicóticos/etiologiaRESUMO
This review aims to present the more recent knowledge on the role of the endocannabinoid system in drug addiction. For a long time, dopamine has been consistently associated with the reinforcing effects of most drugs of abuse but, recently, pharmacological evidence points to the possibility that pharmacological management of the endocannabinoid system might not only block the direct reinforcing effect of cannabis, opioids, nicotine and ethanol, but also prevent the relapse to various drugs of abuse including opioids, cocaine, nicotine, alcohol and amphetamine. Preclinical and clinical studies suggest that the manipulation of the endocannabinoid system through the CB(1) receptor antagonist SR-141716A (rimonabant) might constitute a new therapeutical strategy for treating addiction across different classes of abused drugs.
Assuntos
Moduladores de Receptores de Canabinoides/fisiologia , Transtornos Relacionados ao Uso de Substâncias/fisiopatologia , Alcoolismo/fisiopatologia , Alcoolismo/psicologia , Animais , Estimulantes do Sistema Nervoso Central , Humanos , Transtornos Relacionados ao Uso de Opioides/fisiopatologia , Transtornos Relacionados ao Uso de Opioides/psicologia , Transtornos Relacionados ao Uso de Substâncias/psicologia , Tabagismo/fisiopatologia , Tabagismo/psicologiaRESUMO
How cannabinoids influence immune function has been examined extensively in the last 30 years. Studies on drug-abusing humans and animals, as well as in vitro models employing immune cell cultures, have shown that marijuana, natural and endogenous cannabinoid compounds are immunomodulators. These substances modulate host resistance to bacterial, protozoan and viral infections as well as they can profoundly affect the Th1/Th2 response. Recently, two types of cannabinoid receptor, CB1 and CB2, have been discovered. While CB1 is expressed primarily in the brain, CB2 is peculiar of the immune cells. Cannabinoid receptors have been shown to be involved in some but not all of immune effects. Nevertheless, their identification provides a specific mechanism of action in the attempting to find out how exogenous cannabinoids and endogenous cannabinoid system affect the immune apparatus, strengthen the hypothesis of cannabinoids as immunomodulators. As support to this theory, enough evidence exists to suggest that the cannabinoid system significantly affects almost every component of the immune response machinery and impacts the functioning also of the cytokine network. The evaluation of the biological consequences of these drug-induced cytokine changes has also dramatically become important considering not only the impact of cytokines on immune system per se but also envisaging their influence in cancer, inflammation, autoimmune disease, brain injury, hematopoietic colony formation in which cannabinoids have demonstrated a clear role as important modulators.
Assuntos
Canabinoides/farmacologia , Citocinas/fisiologia , Sistema Imunitário/efeitos dos fármacos , Animais , Canabinoides/química , Humanos , Fatores Imunológicos/química , Fatores Imunológicos/farmacologia , Modelos Biológicos , Estrutura Molecular , Transdução de Sinais/efeitos dos fármacosRESUMO
Cannabidiol is the main nonpsychoactive component of marijuana. We examined the ability of in vivo and in vitro cannabidiol to interfere with the production of interleukin (IL)-12 and IL-10 by murine macrophages and to modulate macrophage chemotaxis. Cannabidiol added in vitro to peritoneal macrophages significantly increased IL-12 and decreased IL-10 production. The CB1 and CB2 receptor antagonists prevented this modulation. Macrophages from animals treated with cannabidiol at the dose of 30 mg kg(-1) either orally or i.p. produced higher levels of IL-12 and lower levels of IL-10 in comparison to controls, and the CB receptor antagonists did not prevent these effects. Cannabidiol dose-dependently decreased fMLP-induced chemotaxis of macrophages, and the CB2 receptor antagonist prevented this decrease.
Assuntos
Adjuvantes Imunológicos/administração & dosagem , Adjuvantes Imunológicos/farmacologia , Canabidiol/administração & dosagem , Canabidiol/farmacologia , Quimiotaxia/efeitos dos fármacos , Interleucina-10/biossíntese , Interleucina-12/biossíntese , Macrófagos Peritoneais/efeitos dos fármacos , Adjuvantes Imunológicos/metabolismo , Administração Oral , Animais , Canfanos/farmacologia , Canabidiol/metabolismo , Inibição de Migração Celular , Células Cultivadas , Quimiotaxia/imunologia , Citocinas/biossíntese , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/imunologia , Interleucina-10/antagonistas & inibidores , Ativação de Macrófagos/efeitos dos fármacos , Ativação de Macrófagos/imunologia , Macrófagos Peritoneais/imunologia , Macrófagos Peritoneais/metabolismo , Masculino , Camundongos , Piperidinas/farmacologia , Pirazóis/farmacologia , Receptor CB1 de Canabinoide/antagonistas & inibidores , Receptor CB1 de Canabinoide/fisiologia , Receptor CB2 de Canabinoide/antagonistas & inibidores , Receptor CB2 de Canabinoide/fisiologia , Rimonabanto , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/imunologiaRESUMO
When Delta(9)-tetrahydrocannabinol (Delta(9)-THC,15 mg/kg) was injected intraperitoneally twice a day for 6 days, tolerance to its analgesic effect appeared to be complete. Chronic exposure to Delta(9)-THC caused a significant reduction in CB1 receptor binding in all brain areas that contain this receptor. Cannabinoid receptor density was markedly reduced in the cerebellum (52%), hippocampus (40%) and globus pallidum (47%) compared to 30% in the cortex and striatum. Chronic exposure enhanced the cAMP pathway, as shown by the significant increase of cAMP levels and PKA activity in the areas with receptor down-regulation (cerebellum, striatum and cortex). We propose that the increase in cAMP cascade is part of the biochemical basis of cannabinoid tolerance.
Assuntos
Encéfalo/enzimologia , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , AMP Cíclico/metabolismo , Dronabinol/farmacologia , Animais , Autorradiografia , Comportamento Animal/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Neoplasias Encefálicas/enzimologia , Neoplasias Encefálicas/metabolismo , Tolerância a Medicamentos , Masculino , Neuroblastoma/enzimologia , Neuroblastoma/metabolismo , Ratos , Ratos Sprague-Dawley , Células Tumorais CultivadasRESUMO
In the present work, we investigated in the rat the possibility of functional interaction between opiate and cannabinoid systems at immune level comparatively with the central nervous system (CNS). Moderate analgesic doses of the synthetic cannabinoid compound CP-55,940 (0.2 mg/kg, i.p.) and morphine (5 mg/kg, s.c.) significantly inhibited the ConA-induced splenocyte proliferation and natural killer (NK) cytolytic activity. The acute co-administration of the two drugs resulted in an enhancement of antinociception while they did not yield any additive inhibition of the immune parameters. The CB1 cannabinoid receptor antagonist N-(Piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716A; 3 mg/kg, i.p.) and the CB2 receptor antagonist N-[(1S)-endo-1,3,3-trimethhyl bicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528; 3 mg/kg, i.p.) did not block the central nor the immune effects of morphine; similarly, the opioid receptor antagonist naloxone did not attenuate CP-55,940-induced effects. Animals tolerant to CP-55,940-induced (0.2 mg/kg, i.p.; twice a day for 4 days) or morphine-induced analgesia (5 mg/kg, s.c.; twice a day for 6 days) also developed tolerance to their acute immunosuppressive effects. Concomitantly, animals became cross-resistant to the immunosuppressive effects while an asymmetric cross-tolerance developed for analgesia. Our data demonstrated the existence of an interaction between cannabinoids and opiates at the immune level that differs from the interaction present in the CNS.
Assuntos
Analgésicos/farmacologia , Canabinoides/farmacologia , Imunossupressores/farmacologia , Entorpecentes/farmacologia , Animais , Cicloexanóis/farmacologia , Interações Medicamentosas , Tolerância a Medicamentos , Masculino , Morfina/farmacologia , Ratos , Ratos Sprague-DawleyRESUMO
Cannabinoids have been shown to affect immune responses, acting on different populations of immune cells. In the present paper we analyze the ability of in vivo and in vitro treatment with the potent synthetic cannabinoid CP55,940 to interfere with an important function of rat peritoneal macrophages, i.e. spontaneous migration and formyl-metionyl-leucine-phenylalanine (fMLP)-induced chemotaxis, that were assessed by the use of a Boyden-modified microchemotaxis chamber. When added in vitro, CP55,940 induced a significant and dose-dependent inhibition of both spontaneous migration and fMLP-induced chemotaxis. Both the Cannabinoid Receptor 1 (CB1) and the Cannabinoid Receptor 2 (CB2) antagonists were able to block the CP55,940-induced inhibition of spontaneous migration, although the CB2 antagonist was more potent and only the CB2 antagonist was able to reverse the effect of CP55,940 on fMLP-induced chemotaxis. Similarly, in the in vivo experiments, 1 h after the acute subcutaneous administration of 0.4 mg/kg of CP55,940, both spontaneous motility and chemotaxis were reduced. The pretreatment with the CB2 antagonist, but not with the CB1 antagonist, was able to prevent this effect. Our data confirm that cannabinoids can affect some macrophage functions, mainly throughout CB2 receptors, and suggest that the development of specific CB2 ligands may lead to an interesting new class of anti-inflammatory drugs.
Assuntos
Movimento Celular/imunologia , Cicloexanóis/farmacologia , Imunossupressores/farmacologia , Macrófagos Peritoneais/citologia , Receptor CB2 de Canabinoide , Receptores de Droga/imunologia , Animais , Canfanos/farmacologia , Canabinoides/antagonistas & inibidores , Canabinoides/farmacologia , Movimento Celular/efeitos dos fármacos , Células Cultivadas , Relação Dose-Resposta a Droga , Técnicas In Vitro , Macrófagos Peritoneais/efeitos dos fármacos , Masculino , Piperidinas/farmacologia , Pirazóis/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de Canabinoides , RimonabantoRESUMO
Changes in mitogen-induced splenocyte proliferation and NK activity were evaluated after acute (1 h) and chronic (6 d) in vivo treatment of rats with the synthetic cannabinoid compound CP-55,940. At a dose of 0.4 mg/kg i.p. it significantly inhibited the splenocyte proliferative response to PHA and NK activity but half this dose (0.2 mg/kg) had no effect on immune responses. Pretreatment of rats with the cannabinoid receptor CB1 antagonist SR141716A did not antagonize the CP-55,940-induced immunosuppression, excluding the activation of this receptor subtype in the mediation of this effect. When immune function studies were done on rats tolerant to CP-55,940-induced analgesia, full tolerance also developed for the inhibition of splenocyte proliferation and NK activity. The data provided indicate that CB1 cannabinoid receptors are not involved in mediating the acute and chronic effects of cannabinoids on the immune system and suggest a possible implication of CB2 receptor although other modalities of CP-55,940 action can not be ruled out.
Assuntos
Canabinoides/administração & dosagem , Cicloexanóis/administração & dosagem , Imunossupressores/administração & dosagem , Receptor CB2 de Canabinoide , Baço/efeitos dos fármacos , Baço/imunologia , Animais , Comportamento Animal/efeitos dos fármacos , Canabinoides/antagonistas & inibidores , Canabinoides/metabolismo , Cicloexanóis/antagonistas & inibidores , Cicloexanóis/metabolismo , Citotoxicidade Imunológica/efeitos dos fármacos , Esquema de Medicação , Imunossupressores/antagonistas & inibidores , Imunossupressores/metabolismo , Injeções Intraperitoneais , Células Matadoras Naturais/efeitos dos fármacos , Ativação Linfocitária/efeitos dos fármacos , Masculino , Piperidinas/administração & dosagem , Pirazóis/administração & dosagem , Ratos , Ratos Sprague-Dawley , Receptores de Canabinoides , Receptores de Droga/antagonistas & inibidores , Rimonabanto , Baço/citologiaRESUMO
We studied the effect of acute (1 h) or chronic exposure (7 and 14 days) to delta9-tetrahydrocannabinol (delta9-THC) on immune parameters in male Swiss mice. One hour after a dose of 10 mg/kg s.c., the splenocyte proliferative response to ConA and NK activity were not inhibited, but there was a significant decrease in the production of IL-2. After 7 days of treatment, when mice were tolerant to delta9-THC-induced analgesia, these functional parameters were strongly inhibited and there was a persistent reduction in IL-2 and IFNgamma. With 14 days exposure to the drug, splenocyte proliferation was significantly reduced only with 5 microg/ml ConA, and NK activity was still significantly depressed (about 37%). IL-2 had returned to the control value, whereas IFNgamma was still 40% down. Flow cytometry analysis of spleen cell composition indicated no changes after the acute and 7 day treatments, but at 14 days there was a 20% decrease in the number of T lymphocytes, mirrored by a 26% increase of B lymphocytes. In conclusion, in vivo exposure to psychoactive doses of delta9-THC has profound effects on immune function. This implies some important questions in relation to the liberalization of marijuana and its therapeutic uses.
Assuntos
Dronabinol/farmacologia , Sistema Imunitário/efeitos dos fármacos , Tolerância Imunológica , Animais , Formação de Anticorpos , Linfócitos B/citologia , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Concanavalina A/farmacologia , Tolerância Imunológica/fisiologia , Interferon gama/antagonistas & inibidores , Interleucina-2/antagonistas & inibidores , Células Matadoras Naturais/efeitos dos fármacos , Células Matadoras Naturais/fisiologia , Contagem de Leucócitos/efeitos dos fármacos , Masculino , Camundongos , Valores de Referência , Baço/citologia , Baço/metabolismo , Linfócitos T/citologiaRESUMO
We used a previously reported model of morphine sensitization that elicited a complex behavioral syndrome involving stereotyped and non stereotyped activity. To identify the mechanism of these long-lasting processes, we checked the density of mu opioid receptors, receptor-G-protein coupling and the cyclic AMP (cAMP) cascade. In morphine-sensitized animals mu opioid receptor autoradiography revealed a significant increase in the caudate putamen (30% versus controls), nucleus accumbens shell (16%), prefrontal and frontal cortex (26%), medial thalamus (43%), hypothalamus (200%) and central gray (89%). Concerning morphine's activation of G proteins in the brain, investigated in the guanylyl 5'-[gamma-(35)S]thio]triphosphate ([(35)S]GTPgammaS) binding assay, a significant increase in net [(35)S]GTPgammaS binding was seen in the caudate putamen (39%) and hypothalamus (27%). In the caudate putamen this was due to an increase in the amount of activated G proteins, and in the hypothalamus to a greater affinity of G proteins for guanosine triphosphate (GTP). The main second messenger system linked to the opioid receptor is the cAMP pathway. In the striatum basal cAMP levels were significantly elevated in sensitized animals (70% versus controls) and [D-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin (DAMGO) significantly inhibited forskolin-stimulated cAMP production in control (30%) but not in sensitized rats. In the hypothalamus no significant changes were observed in basal cAMP levels and DAMGO inhibition. These cellular events induced by morphine pre-exposure could underlie the neuroadaptive processes involved in morphine sensitization.
Assuntos
Química Encefálica/fisiologia , Encéfalo/efeitos dos fármacos , Morfina/farmacologia , Neurônios/efeitos dos fármacos , Transtornos Relacionados ao Uso de Opioides/metabolismo , Receptores Opioides mu/efeitos dos fármacos , Receptores Opioides mu/metabolismo , Animais , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Ligação Competitiva/fisiologia , Encéfalo/metabolismo , Encéfalo/fisiopatologia , Química Encefálica/efeitos dos fármacos , AMP Cíclico/metabolismo , Ala(2)-MePhe(4)-Gly(5)-Encefalina/farmacologia , Proteínas de Ligação ao GTP/efeitos dos fármacos , Proteínas de Ligação ao GTP/metabolismo , Guanosina 5'-O-(3-Tiotrifosfato) , Masculino , Neurônios/metabolismo , Transtornos Relacionados ao Uso de Opioides/fisiopatologia , Ensaio Radioligante , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologiaRESUMO
Prolonged exposure of rats to the synthetic cannabinoid receptor ligand, CP-55,940 (0.4 mg/kg, i.p. for 11 days), induced tolerance to analgesia, to the reduction in spontaneous locomotor activity and the incidence of splayed hind limbs. One hour after the last injection on day 11, the rats were killed and in situ hybridization was used to investigate the effect of treatment on G-protein alpha-subunit expression throughout the brain. Chronic cannabinoid exposure markedly reduced G alpha(s), G alpha(i) and G alpha(o) mRNA levels. The message for the alpha(s)-subunit was decreased in all the brain areas containing the basal autoradiographic signal; the decrease ranging from 25% in the thalamus to 45% in the mesencephalon. Also the basal G alpha(i) expression was reduced in tolerant rats showing the greatest decrease in the forebrain (63%) in the cerebellum (58%) and in the mesencephalon (38%). The reduction in G alpha(o) expression (25%) was more localized, being present only in the rostral portion of the brain (cortex, striatum and olfactory area). The alterations in alpha-subunits gene expression were not followed by any change in the amount of proteins. Our results indicate that, besides the receptor modification, alteration to the G-protein expression could be a molecular event associated with the development of cannabinoid tolerance.
Assuntos
Analgésicos/farmacologia , Encéfalo/efeitos dos fármacos , Canabinoides/farmacologia , Cicloexanóis/farmacologia , Proteínas de Ligação ao GTP/biossíntese , Proteínas do Tecido Nervoso/biossíntese , Animais , Encéfalo/metabolismo , Mapeamento Encefálico , Hibridização In Situ , Masculino , Medição da Dor , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
The in situ hybridization technique was used to investigate the effect on G protein alpha subunit expression throughout the brain of rats chronically infused with naltrexone (70 micrograms/microliters, 1 microliter/h), DAGO (0.5 micrograms/microliter, 1 microliter/h), DADLE (11.4 micrograms/microliters, 1 microliter/h), DPDPE (3.4 micrograms/microliters, 1 microliter/h) and U-50,488H (4 micrograms/microliters, 1 microliter/h). Prolonged exposure to naltrexone did not modify G protein alpha subunit mRNA expression, whereas DADLE and U-50,488H, respectively, increased the levels of alpha s and alpha o mRNA in specific brain regions. In particular, a 15% increase in alpha s expression was only observed in the dorsomedial hypothalamic nucleus of rats undergoing chronic DADLE infusion: a 15% increase in alpha o levels was detected in the claustrum and endopiriform nucleus of rats chronically treated with U-50,488H. These are the first in vivo data to demonstrate that only chronic stimulation with an opioid agonist (morphine and/or DADLE and U-50,488H) is capable of modifying G protein alpha subunit mRNA. The regional selectivity of these modifications is discussed, together with the receptor specificity of the opioid effects.
Assuntos
Encéfalo/metabolismo , Ventrículos Cerebrais/fisiologia , Proteínas de Ligação ao GTP/biossíntese , Expressão Gênica/efeitos dos fármacos , Naltrexona/farmacologia , Entorpecentes/farmacologia , RNA Mensageiro/metabolismo , (trans)-Isômero de 3,4-dicloro-N-metil-N-(2-(1-pirrolidinil)-ciclo-hexil)-benzenoacetamida , Animais , Encéfalo/citologia , Encéfalo/efeitos dos fármacos , Ventrículos Cerebrais/efeitos dos fármacos , Esquema de Medicação , Ala(2)-MePhe(4)-Gly(5)-Encefalina , D-Penicilina (2,5)-Encefalina , Leucina Encefalina-2-Alanina/administração & dosagem , Leucina Encefalina-2-Alanina/farmacologia , Encefalinas/administração & dosagem , Encefalinas/farmacologia , Hibridização In Situ/métodos , Infusões Parenterais , Masculino , Naltrexona/administração & dosagem , Entorpecentes/administração & dosagem , Sondas de Oligonucleotídeos , Especificidade de Órgãos , Pirrolidinas/administração & dosagem , Pirrolidinas/farmacologia , RNA Mensageiro/análise , Ratos , Ratos Sprague-DawleyRESUMO
Intraperitoneal injection of delta9-THC (7.5 mg/kg) in rats made tolerant to morphine by s.c. implantation of morphine pellets had a much greater analgesic effect than in placebo pellet plus delta9-THC treatment. To investigate whether this was due to some change in cannabinoid receptor levels and/or expression induced by chronic morphine, we designed this autoradiographic binding study coupled with in situ hybridization on sagittal sections of the treated rat brains. Binding showed a significant increase in CB1 receptor density (15%) specifically in the caudate-putamen, in parallel with a significant enhancement of CB1 mRNA in the same area (20%). We suggest that morphine chronic treatment leads to a functional modulation between the opioid and cannabinoid systems at least for analgesia in a specific area, in this case the striatum.
Assuntos
Analgésicos Opioides/farmacologia , Analgésicos/farmacologia , Dronabinol/farmacologia , Morfina/farmacologia , Receptores de Droga/efeitos dos fármacos , Animais , Autorradiografia , Química Encefálica/efeitos dos fármacos , Tolerância a Medicamentos , Hibridização In Situ , Masculino , Medição da Dor/efeitos dos fármacos , RNA Mensageiro/biossíntese , Ratos , Ratos Sprague-Dawley , Receptores de Canabinoides , Receptores de Droga/biossínteseRESUMO
Using in situ hybridization we found that chronic treatment with CP-55,940 (0.4 mg kg-1, i.p. daily for 11 days), a synthetic cannabinoid receptor ligand, changed cannabinoid receptor mRNA levels in rat brain. CP-55,940 produced the expected tolerance: the decrease in locomotor activity (75%) caused by an acute dose was diminished to 25% after the 11 days of treatment. Thirty minutes after the last injection the animals were killed and in situ hybridization indicated that the levels of cannabinoid receptor mRNA in the caudate-putamen were reduced by 33%, with no alteration in the other brain areas. We suggest that the altered cannabinoid receptor expression is part of the adaptive changes underlying cannabinoid tolerance.
Assuntos
Encéfalo/metabolismo , Cicloexanóis/farmacologia , RNA Mensageiro/metabolismo , Receptores de Droga/genética , Animais , Canabinoides/farmacologia , Hibridização In Situ , Masculino , Atividade Motora/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptores de Canabinoides , Receptores de Droga/efeitos dos fármacos , Fatores de TempoRESUMO
Dermorphin (DM), microinjected at 0.4 nmoles/rat into various sites of the periaqueductal gray matter (PAG), provokes complete inhibition of intestinal propulsion always coupled with full analgesia and catalepsy. When electrolytic lesions were made in the raphe magnus nucleus (NRM) a slight but significant reduction of intestinal inhibition evoked by DM into the PAG was observed. In contrast, pretreatment into the NRM 10 days before DM with a selective antiserotoninergic agent (5,6 DHT 15 microgram/rat), did not influence intestinal inhibition. As expected, both lesions reduced DM-induced analgesia but catalepsy was not affected. DM-induced inhibition of intestinal transit was therefore unaffected by subdiaphragmatic vagotomy. Finally, some other central brain regions were found sensitive to DM for the above effects such as the lateral and medial hypothalamus and mid-line thalamus. Negative results were obtained for the supraoptic nuclei and postero-medial cortical amygdaloid nucleus. Some considerations are put forward about the existence in the central nervous system of selective areas involved in intestinal modulation and their relationship with those mediating other opiate behavioural effects.