RESUMO
Hallucinogens, including mescaline, psilocybin, and lysergic acid diethylamide (LSD), profoundly affect perception, cognition, and mood. All known drugs of this class are 5-HT(2A) receptor (2AR) agonists, yet closely related 2AR agonists such as lisuride lack comparable psychoactive properties. Why only certain 2AR agonists are hallucinogens and which neural circuits mediate their effects are poorly understood. By genetically expressing 2AR only in cortex, we show that 2AR-regulated pathways on cortical neurons are sufficient to mediate the signaling pattern and behavioral response to hallucinogens. Hallucinogenic and nonhallucinogenic 2AR agonists both regulate signaling in the same 2AR-expressing cortical neurons. However, the signaling and behavioral responses to the hallucinogens are distinct. While lisuride and LSD both act at 2AR expressed by cortex neurons to regulate phospholipase C, LSD responses also involve pertussis toxin-sensitive heterotrimeric G(i/o) proteins and Src. These studies identify the long-elusive neural and signaling mechanisms responsible for the unique effects of hallucinogens.
Assuntos
Comportamento Animal/efeitos dos fármacos , Córtex Cerebral/efeitos dos fármacos , Alucinógenos/farmacologia , Receptor 5-HT2A de Serotonina/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Anfetaminas , Animais , Autorradiografia , Ligação Competitiva/efeitos dos fármacos , Células Cultivadas , Córtex Cerebral/citologia , Eletrofisiologia , Hibridização in Situ Fluorescente , Ketanserina/farmacologia , Lisurida/farmacologia , Masculino , Camundongos , Camundongos Knockout , Células Piramidais/efeitos dos fármacos , Células Piramidais/fisiologia , Receptor 5-HT2A de Serotonina/genética , Receptores de Dopamina D1/efeitos dos fármacos , Receptores de Dopamina D2/efeitos dos fármacos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Antagonistas da Serotonina/farmacologia , Agonistas do Receptor de Serotonina/farmacologiaRESUMO
OBJECTIVE: To study the hyperacute histological and immunohistochemical effects of stereotactic proton beam irradiation of the rat hippocampus. METHODS: Nine rats underwent proton beam radiosurgery of one hippocampus with nominal doses of cobalt-2, -12, and -60 Gray equivalents (n = 3 each). Control animals (n = 3) were not irradiated. Animals were killed 5 hours after irradiation and brain sections were stained for Nissl, silver degeneration, deoxyribonucleic acid (DNA) fragmentation (DNAF), and the activated form of two mitogen-activated protein kinases (MAPKs), phospho-Erk1/2 (P-Erk1/2) and p38. Stained cells in the hippocampus expressing DNAF and/or P-Erk1/2 were counted. Confocal microscopy with double immunofluorescent staining was used to examine cellular colocalization of DNAF and P-Erk1/2. RESULTS: Both DNAF and P-Erk1/2 showed quantitative dose-dependent increases in staining in the targeted hippocampus compared with the contralateral side and controls. This finding was restricted to the subgranular proliferative zone of the hippocampus. Both markers also were up-regulated on the contralateral side when compared with controls in a dose-dependent fashion. Simultaneous staining for DNAF and P-Erk1/2 was found in fewer than half of all cells. p38 was unchanged compared with controls. Although Nissl staining appeared normal, silver stain confirmed dose-dependent cellular degeneration. CONCLUSION: DNAF, a marker of cell death, was present in rat hippocampi within 5 hours of delivery of cobalt-2 Gray equivalents stereotactically focused irradiation, suggesting that even low-dose radiosurgery has hyperacute neurotoxic effects. Activated mitogen-activated protein kinase was incompletely colocalized with DNAF, suggesting that activation of this cascade is neither necessary nor sufficient to initiate acute cell death after irradiation.
Assuntos
Regulação da Expressão Gênica/efeitos da radiação , Hipocampo/efeitos da radiação , Radiação Ionizante , Radiocirurgia/efeitos adversos , Animais , Contagem de Células/métodos , Fragmentação do DNA/efeitos da radiação , Relação Dose-Resposta à Radiação , Hipocampo/metabolismo , Hipocampo/patologia , Hipocampo/fisiopatologia , Imuno-Histoquímica/métodos , Imageamento por Ressonância Magnética/métodos , Masculino , Microscopia Confocal/métodos , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Quinases de Proteína Quinase Ativadas por Mitógeno/metabolismo , Neurônios/efeitos da radiação , Ratos , Ratos Sprague-Dawley , Coloração pela Prata/métodos , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
BACKGROUND AND PURPOSE: This work was undertaken to determine to what degree long-term neurofunctional outcome of neonatal hypoxic-ischemic (HI) brain injury in mice correlates with anatomical extent of cerebral damage assessed by magnetic resonance imaging (MRI) and histopathology. METHODS: On postnatal day 7, mice were subjected to HI. At 7 to 9 weeks after HI neurofunctional outcome was assessed by water-maze, rota-rod, and open-field test performance, followed by cerebral MRI and histopathology evaluation. RESULTS: At 10 weeks after HI, MRI revealed ipsilateral brain atrophy alone or with porencephalic cyst formation and contralateral ventriculomegaly. Adult HI-affected mice, especially those that developed a porencephalic cyst, demonstrated significant neurofunctional deficit compared with age-matched naïve mice. HI-affected mice with ipsilateral cerebral atrophy but without porencephaly demonstrated no or an intermediate level of neurofunctional deficit. Neurobehavioral assessment of mice subjected to HI insult revealed a strong correlation between degree of brain injury and functional neurohandicap. CONCLUSIONS: This is the first study to demonstrate that long-term neurofunctional outcome in mice after a neonatal HI correlates tightly with anatomical pattern/extent of cerebral damage, defined by MRI and histopathology.
Assuntos
Ataxia/etiologia , Dano Encefálico Crônico/etiologia , Encéfalo/patologia , Hipóxia-Isquemia Encefálica/complicações , Deficiências da Aprendizagem/etiologia , Testes Neuropsicológicos , Animais , Animais Recém-Nascidos , Ataxia/patologia , Atrofia , Dano Encefálico Crônico/patologia , Encefalopatias/etiologia , Encefalopatias/patologia , Artéria Carótida Primitiva , Ventrículos Cerebrais/patologia , Cistos/etiologia , Cistos/patologia , Comportamento Exploratório , Feminino , Hipóxia-Isquemia Encefálica/patologia , Deficiências da Aprendizagem/patologia , Ligadura , Imageamento por Ressonância Magnética , Masculino , Aprendizagem em Labirinto , Camundongos , Camundongos Endogâmicos C57BL , Atividade Motora , Plasticidade NeuronalRESUMO
BACKGROUND: As a key regulator of serotonergic activity and target of many antidepressant treatments, the serotonin transporter (SERT) represents a potential mediator of anxiety- and depression-related behaviors. Using mice lacking the SERT (SERT KO), we examined the role of SERT function in anxiety- and depression-related behaviors and serotonergic neuron function. METHODS: Serotonin transporter knockout mice were evaluated in paradigms designed to assess anxiety-, depression-, and stress-related behaviors. Dorsal raphe nucleus (DRN) function was assessed by quantitative serotonergic cell counting and extracellular electrical recording of neuronal firing properties. RESULTS: Serotonin transporter knockout mice showed an increase in latency to feed in a novel situation, more immobility in a forced swim, increased escape latency in a shock escape paradigm, and decreased immobility in tail suspension. No differences in anxiety-related behaviors were seen in the open field and the elevated plus maze. Serotonin transporter knockout mice exhibit a 50% reduction in serotonergic cell number and a fourfold decrease in firing rate in the DRN. CONCLUSIONS: Developmental loss of SERT produces altered behaviors in models of depression that are generally opposite to those produced by antidepressant treatment. The reduced serotonergic cell number and firing rate in the DRN of adult SERT KO mice suggest a mechanism for these altered behaviors.
Assuntos
Proteínas de Transporte/metabolismo , Depressão/fisiopatologia , Glicoproteínas de Membrana/metabolismo , Proteínas de Membrana Transportadoras , Proteínas do Tecido Nervoso , Núcleos da Rafe/fisiopatologia , Potenciais de Ação , Analgesia , Animais , Ansiedade/metabolismo , Ansiedade/fisiopatologia , Autorradiografia , Aprendizagem da Esquiva , Comportamento Animal , Proteínas de Transporte/genética , Contagem de Células , Depressão/metabolismo , Relação Dose-Resposta à Radiação , Eletrofisiologia/métodos , Eletrochoque/métodos , Reação de Fuga , Comportamento Exploratório , Comportamento Alimentar , Feminino , Elevação dos Membros Posteriores , Imuno-Histoquímica , Isótopos de Iodo/farmacocinética , Masculino , Maleatos/farmacocinética , Aprendizagem em Labirinto , Glicoproteínas de Membrana/deficiência , Glicoproteínas de Membrana/genética , Camundongos , Camundongos Transgênicos , Núcleos da Rafe/metabolismo , Tempo de Reação , Proteínas da Membrana Plasmática de Transporte de Serotonina , Estresse Fisiológico/metabolismo , Estresse Fisiológico/fisiopatologia , Natação , Fatores de TempoRESUMO
OBJECTIVE: To explore the histological, electrophysiological, radiological, and behavioral effects of radiosurgery using a new model of proton beam radiosurgery (PBR) of the rodent hippocampus. METHODS: Forty-one rats underwent PBR of the right hippocampus with nominal doses of 5 to 130 cobalt Gray equivalents (CGE). Three control animals were untreated. Three months after PBR, 41 animals were evaluated with the Morris water maze, 23 with T2-weighted magnetic resonance imaging, and 22 with intrahippocampal microelectrode recordings. Animals that were studied physiologically were killed, and their brains were examined with Nissl staining and immunocytochemical staining for glutamic acid decarboxylase, heat shock protein 72 (HSP-72), parvalbumin, calmodulin, calretinin, calbindin, and somatostatin. RESULTS: Ninety and 130 CGE resulted in decreased performance in the Morris water maze, increased signal on T2-weighted magnetic resonance imaging, diminished granule cell field potentials, and tissue necrosis, which was restricted to the irradiated side. These doses also resulted in ipsilateral up-regulation of calbindin and HSP-72. Parvalbumin was down-regulated at 130 CGE. The 30 and 60 CGE animals displayed a marked increase in HSP-72 staining on the irradiated side but no demonstrable cell loss. No asymmetries were noted in somatostatin, calretinin, and glutamic acid decarboxylase staining. Normal physiology was found in rats receiving up to 60 CGE. CONCLUSION: This study expands our understanding of the effects of radiosurgery on the mammalian brain. Three months after PBR, the irradiated rat hippocampus demonstrates necrosis at 90 CGE, but not at 60 CGE, with associated abnormalities in magnetic resonance imaging, physiology, and memory testing. HSP-72 was up-regulated at nonnecrotic doses.
Assuntos
Comportamento Animal , Hipocampo/fisiopatologia , Hipocampo/cirurgia , Imageamento por Ressonância Magnética , Radiocirurgia , Animais , Benzoxazinas , Encéfalo/patologia , Corantes , Eletrofisiologia , Potenciais Pós-Sinápticos Excitadores , Hipocampo/metabolismo , Hipocampo/patologia , Imuno-Histoquímica , Masculino , Memória , Necrose , Oxazinas , Ratos , Ratos Sprague-DawleyRESUMO
Birth asphyxia accounts for the majority of developmental motor and cognitive deficits. Studies were undertaken to develop a reproducible murine model of perinatal hypoxic-ischemic encephalopathy (HIE) which would permit both anatomic and neurofunctional quantification of injury. Short-term neurofunctional outcomes consisted of three developmental reflexes (righting, cliff aversion and geotaxis) assessed in 7-day-old mouse pups 24 h after unilateral carotid artery ligation followed by inhalation of 8% oxygen. Cerebral infarct volume was dependent on duration of hypoxia, being approximately 2.5-fold greater with longer (60 min) versus shorter (30 min) hypoxia exposure (P=0.001). All three sensorimotor neonatal reflexes assessed at 24 h after HIE injury correlated significantly with long-term neurofunction evaluated using a water-maze test of navigational learning and memory assessed 8 weeks later in the same animals. Cerebral atrophy, a delayed consequence of HIE in this model, also correlated strongly with water-maze performance (r=0.86, P=0.002). These data demonstrate for the first time that murine neonatal sensorimotor reflex performance can be rigorously quantified in the acute phase of perinatal HIE and has strong predictive value not only for anatomic extent of cerebral injury, but also for long-term neurofunctional outcome.