Increased Alcohol Seeking in Mice Lacking Gpr88 Involves Dysfunctional Mesocorticolimbic Networks.

BACKGOUND: Alcohol use disorder (AUD) is devastating and poorly treated, and innovative targets are actively sought for prevention and treatment. The orphan G protein-coupled receptor GPR88 is enriched in mesocorticolimbic pathways, and Gpr88 knockout mice show hyperactivity and risk-taking behavior, but a potential role for this receptor in drug abuse has not been examined. METHODS: We tested Gpr88 knockout mice for alcohol-drinking and -seeking behaviors. To gain system-level understanding of their alcohol endophenotype, we also analyzed whole-brain functional connectivity in naïve mice using resting-state functional magnetic resonance imaging. RESULTS: Gpr88 knockout mice showed increased voluntary alcohol drinking at both moderate and excessive levels, with intact alcohol sedation and metabolism. Mutant mice also showed increased operant responding and motivation for alcohol, while food and chocolate operant self-administration were unchanged. Alcohol place conditioning and alcohol-induced dopamine release in the nucleus accumbens were decreased, suggesting reduced alcohol reward in mutant mice that may partly explain enhanced alcohol drinking. Seed-based voxelwise functional connectivity analysis revealed significant remodeling of mesocorticolimbic centers, whose hallmark was predominant weakening of prefrontal cortex, ventral tegmental area, and amygdala connectional patterns. Also, effective connectivity from the ventral tegmental area to the nucleus accumbens and amygdala was reduced. CONCLUSIONS: Gpr88 deletion disrupts executive, reward, and emotional networks in a configuration that reduces alcohol reward and promotes alcohol seeking and drinking. The functional connectivity signature is reminiscent of alterations observed in individuals at risk for AUD. The Gpr88 gene, therefore, may represent a vulnerability/resilience factor for AUD, and a potential drug target for AUD treatment.

Cafeteria diet induces neuroplastic modifications in the nucleus accumbens mediated by microglia activation.

High-palatable and caloric foods are widely overconsumed due to hedonic mechanisms that prevail over caloric necessities leading to overeating and overweight. The nucleus accumbens (NAc) is a key brain area modulating the reinforcing effects of palatable foods and is crucially involved in the development of eating disorders. We describe that prolonged exposure to high-caloric chocolate cafeteria diet leads to overeating and overweight in mice. NAc functionality was altered in these mice, presenting structural plasticity modifications in medium spiny neurons, increased expression of neuroinflammatory factors and activated microglia, and abnormal responses after amphetamine-induced hyperlocomotion. Chronic inactivation of microglia normalized these neurobiological and behavioural alterations exclusively in mice exposed to cafeteria diet. Our data suggest that prolonged exposure to cafeteria diet produces neuroplastic and functional changes in the NAc that can modify feeding behaviour. Microglia activation and neuroinflammation play an important role in the development of these neurobiological alterations.

Role of DOR in neuronal plasticity changes promoted by food-seeking behaviour.

Several lines of evidence support that food overconsumption may be related to the role of the endogenous opioid system in the control of food palatability. The opioid system, and particularly the delta opioid receptor (DOR), plays a crucial role in the regulation of food rewarding properties. In our study, we used operant conditioning maintained by chocolate-flavoured pellets to investigate the role of DOR in the motivation for palatable food and the structural plasticity changes promoted by this behaviour. For this purpose, we evaluated the specific role of this receptor in the behavioural and neuroplastic changes induced by palatable food in the prefrontal cortex (PFC), hippocampus (HCP) and nucleus accumbens (NAc) in constitutive knockout (KO) mice deficient in DOR. Mutant mice and their wild-type littermates were trained to obtain chocolate-flavoured pellets on fixed ratio 1 (FR1), FR5 and progressive ratio (PR) schedule of reinforcement. No significant differences between genotypes were revealed on operant behaviour acquisition in FR1. DOR knockout mice displayed lower number of active lever-presses than wild-type mice on FR5, and a similar decrease was revealed in DOR KO mice in the breaking point during the PR. This operant training to obtain palatable food increased dendritic spine density in the PFC, HCP and NAc shell of wild-type, but these plasticity changes were abolished in DOR KO mice. Our results support the hypothesis that DOR regulates the reinforcing effects and motivation for palatable food through neuroplastic changes in specific brain reward areas.

Anxiolytic-like effect of Rauvolfia ligustrina Willd: ex Roem. & Schult., Apocynaceae, in the elevated plus-maze and hole-board tests / Avaliação do efeito ansiolítico de Rauvolfia ligustrina Willd: ex Roem. & Schult., Apocynaceae, nos testes do labirinto em cruz elevado e placa-perfurada

Rauvolfia ligustrina Willd. ex Roem. & Schult. (Apocynaceae), popularly known as "arrebenta-boi" and "paratudo". In behavioral screening ethanol extract of R. ligustrina roots demonstrated depressant effect on the CNS and anticonvulsant properties. The purpose of this study was to characterize the putative anxiolytic-like effects of the ethanol extract of Rauvolfia ligustrina roots (EER) using the elevated plus maze (EPM) and the hole-board apparatus in rodents. This extract, administered intraperitoneally, in different doses (3.9, 7.8 and 15.6 mg/kg) was able to increase significantly the number of entries (p < 0.05), as well as the time spent in the open arms of the EPM, indicating an anxiolytic-like effect. Additionally, EER-treated (3.9 and 7.8 mg/kg) increased significantly the number of border visit and head-dipping. This data suggest an anxiolytic effect of EER in animal models of anxiety.

Rauvolfia ligustrina Willd. ex Roem. & Schult. (Apocynaceae) é conhecida popularmente como "arrebenta-boi" e "paratudo". Em triagem farmacológica comportamental o extrato etanólico das raízes de R. ligustrina (EER) mostrou efeito depressor do SNC e propriedades anticonvulsivantes. O presente estudo buscou avaliar o possível efeito ansiolítico do EER utilizando os testes do labirinto em cruz elevado (LCE) e o teste da placa perfurada ("hole-board") em roedores. A administração do EER, por via intraperitoneal (i.p.), em diferentes doses (3,9; 7,8 e 15,6 mg/kg) foi capaz de aumentar significativamente o número de entradas (p < 0,05), assim como o tempo despendido nos braços abertos do LCE. Além disso, nos animais tratados com o EER (3,9 e 7,8 mg/kg, i.p.) ocorreu aumento significativo no número de visitas à borda e mergulho com a cabeça no teste da placa perfurada em comparação com os animais do grupo controle. Estes dados sugerem um possível efeito ansiolítico do EER nos modelos animais testados.

Antidepressant effects of total tertiary alkaloid fraction of Cissampelos sympodialis Eichler in rodents / Efeitos antidepressivos da fração de alcalóides terciários totais de Cissampelos sympodialis Eichler em roedores

A proposta deste trabalho foi de avaliar os efeitos da fração de alcalóides terciários totais (TTAF) de Cissampelos sympodialis Eichler (Menispermaceae) em dois modelos animais de depressão: a) teste do nado forçado e b) teste da reserpina. O tratamento de camundongos com TTAF (12,5 mg/kg) reduziu o tempo total de imobilidade dos animais. Também reverteu a hipotermia induzida por reserpina, demonstrando um efeito antidepressivo nos dois modelos. Adicionalmente, o tratamento com TTAF não modificou a ambulação e o comportamento de levantar das patas dianteiras dos animais avaliados no teste do campo aberto, realizado no intuito de investigar se a redução no tempo de imobilidade apresentada no teste do nado forçado foi causada por estimulação na atividade locomotora. Como a warifteína é um dos principais alcalóides presente na TTAF da C. sympodialis, e tem atividade inibidora da enzima fosfodiesterase, ela pode ser responsável pelo efeito antidepressivo observado na fração estudada.

The purpose of the present study was to evaluate the effects of total tertiary alkaloid fraction (TTAF) of Cissampelos sympodialis Eichler (Menispermaceae) on two animal models of depression: a) forced swim test and b) reserpine test. Treatment of mice with TTAF (12.5 mg/kg) reduced the total immobility time. It also reversed the reserpine-induced hypothermia, demonstrating an antidepressant effect in both models. Additionally, TTAF treatment did not modify the ambulation and rearing evaluated in open field test in order to investigate if the immobility time reduction found in the forced swimming test was caused by locomotive activity stimulation. Since warifteine is one of the main alkaloids present in the TTAF of C. sympodialis, and it has inhibitory activity of the phosphodiesterase enzyme, it may be responsible by the antidepressant effect found in the fraction studied.

Papel da serotonina nas conseqüências comportamentais do estresse

Para testar a hipótese de que a serotonina (5-ht) modula respostas para eventos aversivos, ratos foram submetidos a 2h de imobilização forçada e testados no labirinto em cruz elevado 24h após. Os animais previamente estressados têm uma exploração reduzida, o que foi atenuado por tratamento subcrônico em clorimipramina, um bloqueador de recaptação de 5-ht (12,5mg/kg, ip, 24, 18 e 1h pré-estresse), ou por injeção pós-estresse de 5-medmt, um agonista 5-ht não seletivo (2,5mg/kg ip). O isolamento reduz a exploração nos braços abertos do labirinto em cruz elevado. Ratos também foram submetidos à cirurgia estereotáxica para implantação de cânulas no hipocampo dorsal. Entre 5 e 7 dias após a cirurgia eles foram submetidos à imobilização forçada durante 2h e imediatamente depois receberam microinjeções bilaterais de salina (0,5'MICRO'l) ou 5-medmt (20nmol) dentro do hipocampo dorsal. A droga atenuou a redução da exploração nos braços abertos, devido à imobilização forçada 24h antes. O efeito da droga foi bloqueado por microinjeção prévia de (+) way 100,135 (40nmol), um antagonista de receptores 5-ht1a. Ratos também foram submetidos à cirurgia esterotáxica para receber microinjeção de 5,7-dihidroxitriptamina nos núcleos dorsal da rafe (ndr) e mediano. A lesão no nmr aumenta a atividade exploratória na arena circular, mas não no labirinto em cruz elevado 7 dias após a cirurgia (AU)