RESUMO
Genetically-altered mice, lacking functional NK1 receptors (NK1R-/-), express abnormal behaviours that are prominent in Attention Deficit Hyperactivity Disorder: namely, inattentiveness and impulsivity (indicated by their greater % omissions and premature responses in the 5-Choice Serial Reaction-Time Task (5-CSRTT) and locomotor hyperactivity. We investigated how behaviour in the 5-CSRTT is affected by repeated testing and whether the abnormalities expressed by NK1R-/- mice are mimicked by treating wild type mice with a NK1R antagonist (L 733060 or RP 67580; 5 or 10 mg/kg). Repeated testing with a variable (VITI) or fixed, prolonged (LITI) intertrial interval reduced % omissions. Premature responses also declined, but only in NK1R-/- mice, in the VITI test. By contrast, perseveration increased in both genotypes. RP 67580 (10 mg/kg) increased the % omissions in both genotypes in the VITI, an action which cannot be attributed to NK1R antagonism. Neither drug affected perseveration. However, for premature responses, the response profile suggested that the low and high doses of RP 67580 (VITI) and L 733060 (LITI) had opposing effects on this behaviour. We infer that the effect of NK1R antagonists in the 5-CSRTT is confounded by animals' test experience and non-specific drug effects at sites other than NK1R, possibly L-type Ca²âº(v) channels.
Assuntos
Comportamento de Escolha/efeitos dos fármacos , Antagonistas dos Receptores de Neurocinina-1/farmacologia , Tempo de Reação/efeitos dos fármacos , Receptores da Neurocinina-1/metabolismo , Animais , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Comportamento de Escolha/fisiologia , Masculino , Camundongos , Camundongos Knockout , Tempo de Reação/genética , Receptores da Neurocinina-1/genéticaRESUMO
RATIONALE: Reversal learning deficits are a feature of many human psychopathologies and their associated animal models and have recently been shown to involve the 5-HT(2C) receptor (5-HT(2C)R). Successful reversal learning can be reduced to two dissociable cognitive mechanisms, to dissipate associations of previous positive (opposed by perseverance) and negative (opposed by learned non-reward) valence. OBJECTIVES: This study aims to explore the effect of reducing activity at the 5-HT(2C)R on the cognitive mechanisms underlying spatial reversal learning in the mouse. METHODS: Experiment 1 used the 5-HT(2C)R antagonist SB242084 (0.5 mg/kg) in a between-groups serial design, experiment 2 used 5-HT(2C)R KO mice in a repeated measures design. Animals initially learned to discriminate between two lit nosepoke holes. This was followed by three conditions; (1) full reversal, where contingencies reversed; (2) perseverance, where the previous CS+ became CS- and the previous CS- was replaced by a novel CS+; (3) learned non-reward, where the previous CS- became CS+ and the previous CS+ was replaced by a novel CS-. RESULTS: SB242084 treated and 5-HT(2C)R KO mice showed enhanced reversal learning seen as a decrease in trials, correct responses, and omissions to criterion in the full reversal condition. Similar effects were observed in the learned non-reward condition but SB242084 treated and 5-HT(2C)R KO mice did not differ from controls in the perseverance condition. SB242084 treated, but not 5-HT(2C)R KO mice, showed decreases in all latency indices in every condition. CONCLUSION: Reducing activity at the 5-HT(2C)R facilitates reversal learning in the mouse by reducing the influence of previously non-rewarded associations.
Assuntos
Aminopiridinas/farmacologia , Indóis/farmacologia , Receptor 5-HT2C de Serotonina/metabolismo , Reversão de Aprendizagem/efeitos dos fármacos , Antagonistas do Receptor 5-HT2 de Serotonina/farmacologia , Animais , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Recompensa , Fatores de TempoRESUMO
The presynaptic protein alpha-synuclein, associated with Parkinson's Disease (PD), plays a role in dopaminergic neurotransmission and is implicated in impulse control disorders (ICDs) such as drug addiction. In this study we investigated a potential causal relationship between alpha-synuclein and impulsivity, by evaluating differences in motor impulsivity in the 5-choice serial reaction time task (5-CSRTT) in strains of mice that differ in the expression of the alpha-synuclein gene. C57BL/6JOlaHsd mice differ from their C57BL/6J ancestors in possessing a chromosomal deletion resulting in the loss of two genes, snca, encoding alpha-synuclein, and mmrn1, encoding multimerin-1. C57BL/6J mice displayed higher impulsivity (more premature responding) than C57BL/6JOlaHsd mice when the pre-stimulus waiting interval was increased in the 5-CSRTT. In order to ensure that the reduced impulsivity was indeed related to snca, and not adjacent gene deletion, wild type (WT) and mice with targeted deletion of alpha-synuclein (KO) were tested in the 5-CSRTT. Similarly, WT mice were more impulsive than mice with targeted deletion of alpha-synuclein. Interrogation of our ongoing analysis of impulsivity in BXD recombinant inbred mouse lines revealed an association of impulsive responding with levels of alpha-synuclein expression in hippocampus. Expression of beta- and gamma-synuclein, members of the synuclein family that may substitute for alpha-synuclein following its deletion, revealed no differential compensations among the mouse strains. These findings suggest that alpha-synuclein may contribute to impulsivity and potentially, to ICDs which arise in some PD patients treated with dopaminergic medication.
Assuntos
Tomada de Decisões/fisiologia , Comportamento Impulsivo/genética , Tempo de Reação/genética , alfa-Sinucleína/genética , Animais , Comportamento Animal/fisiologia , Hipocampo/metabolismo , Masculino , Camundongos , Camundongos Knockout , alfa-Sinucleína/metabolismo , gama-Sinucleína/genética , gama-Sinucleína/metabolismoRESUMO
BACKGROUND: The largest cause of neurological damage to children is prenatal exposure to alcohol and chronic alcohol use in adults is associated with neurodegeneration, dementia and long-term behavioral changes. Microarray analysis identified the DNA damage response (DDR) gene, Fanconi anemia (Fanc) D2, to be robustly upregulated in mouse midbrain following 24-hour in vivo exposure to ethanol. In this study, we investigate the ability of ethanol to generate DNA strand breaks, predicted substrates for the Fanc pathway and the potential role of FANCD2 in the DDR to ethanol in brain. METHODS: The effect of ethanol on FANCD2 mRNA levels was measured by quantitative real time PCR using mouse brain and human neuronal cells. FANCD2 protein levels and ubiquitination were measured by Western blotting and immunocytochemistry. DNA damage induction by ethanol/acetaldehyde was measured using the Comet assay and gamma H2AX immunocytochemistry. Levels of DNA and RNA synthesis were measured in cell strains using (3)H-thymidine or (3)H-uridine up-take. RESULTS: Chronic exposure to ethanol induced FANCD2 in mouse midbrain in vivo and in the nucleus of human neuronal cells in culture. However, there was no concomitant increase in the amount of ubiquitinated FANCD2. Acetaldehyde also induced nonubiquitinated FANCD2 protein, and we were able to demonstrate the ability of acetaldehyde to generate DNA double strand breaks, lesions which normally induce ubiquitination of FANCD2. Ethanol also inhibited both RNA and DNA synthesis in proliferating cells consistent with effects on transcription and replication. CONCLUSION: In contrast to other DNA damaging agents, ethanol/acetaldehyde generated DNA strand breaks without inducing ubiquitination of FANCD2, despite increasing protein levels in the nucleus. These data are consistent with recent reports that suggest the Fanconi anemia pathway plays an important role in the adult brain in response to DNA damage. Further work is required to establish what this role is, in particular the potential function of nonubiquitinated FANCD2 and its role in the DNA damage response in postmitotic neurons and neural precursor cells.
Assuntos
Consumo de Bebidas Alcoólicas/metabolismo , Encéfalo/metabolismo , Depressores do Sistema Nervoso Central/farmacologia , Dano ao DNA/efeitos dos fármacos , Etanol/farmacologia , Proteína do Grupo de Complementação D2 da Anemia de Fanconi/metabolismo , Acetaldeído/farmacologia , Animais , Linhagem Celular , Núcleo Celular/metabolismo , DNA/biossíntese , Histonas/metabolismo , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , RNA/biossínteseRESUMO
DNA microarray analysis was used to identify candidate ethanol-regulated genes, as a first step towards exploring how transcriptional changes might lead to ethanol-induced changes in behaviour. Mice were treated with a single acute intraperitoneal ethanol dose and DNA microarray analysis performed on midbrain 2 h posttreatment. We predicted that if ethanol-regulated genes contribute towards behaviour, then constitutive variation in brain expression levels may also contribute to strain-specific differences in ethanol-related behaviour of inbred mouse strains. On the basis of this assumption, we interrogated the BXD inbred strain phenotype database and the U74Av2 MAS5 brain expression database using the WebQTL tool (http://www.genenetwork.org/) and correlated ethanol-related behaviours to expression levels. Constitutive expression levels of 70/90 candidate genes, identified from the DNA microarray analysis, varied significantly between inbred strains and correlated significantly with strain-specific differences in ethanol-related behaviours. These genes were then mapped onto biochemical pathways using Stratagene's PathwayAssist software. This analysis identified the transcription factor Sp1 and NFkappaB pathways in the acute response to ethanol. Ethanol regulation of Sp1 transcription was conserved between humans and mouse. As predicted, downstream targets of Sp1 were also ethanol regulated. NFkappaBia, an important regulator of NFkappaB function and Rela, an NFkappaB-binding partner, were both regulated by ethanol. Expression of both Sp1 and NFkappaBialpha were also downregulated following chronic ethanol treatment. As Sp1 and NFkappaB are implicated in plasticity and behaviour, our data suggest a role for these transcription factors in the long-term behavioural adaptations to ethanol.
Assuntos
Comportamento Animal/efeitos dos fármacos , Etanol/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Mesencéfalo/metabolismo , Subunidade p50 de NF-kappa B/metabolismo , Fator de Transcrição Sp1/metabolismo , Adaptação Fisiológica/efeitos dos fármacos , Animais , Comportamento Animal/fisiologia , Depressores do Sistema Nervoso Central/farmacologia , Bases de Dados de Ácidos Nucleicos , Regulação para Baixo , Perfilação da Expressão Gênica , Masculino , Mesencéfalo/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Subunidade p50 de NF-kappa B/efeitos dos fármacos , Análise de Sequência com Séries de Oligonucleotídeos , Transdução de Sinais/efeitos dos fármacos , Fator de Transcrição Sp1/efeitos dos fármacos , Fatores de TempoRESUMO
Withdrawal from chronic treatment with benzodiazepines is associated with increased neuronal excitability leading to anxiety, aversive effects and increased seizure sensitivity. After repeated withdrawal experiences, seizure sensitivity increases while withdrawal-induced anxiety and aversion decrease. We used autoradiographical methods employing [(3)H]Ro48 8587, a selective ligand for glutamatergic alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors, to study withdrawal-induced changes in AMPA receptor binding in areas of the mouse brain postulated to be involved in these responses. Mice were given 21 days treatment with diazepam (15 mg/kg, s.c. in sesame oil) followed by withdrawal (single withdrawal) or three blocks of 7 days treatment interspersed with 3-day periods to allow washout of drug (repeated withdrawal). In keeping with heightened excitability in withdrawal from chronic diazepam treatment, the single withdrawal group showed, 72 h after their final dose of diazepam, increased [(3)H]Ro48 8587 binding in several brain areas associated with emotional responses or seizure activity, including hippocampal subfields, amygdalar and thalamic nuclei and motor cortex. In contrast, the repeated withdrawal group showed no changes in [(3)H]Ro48 8587 binding in any brain area studied. These observations are consistent with up-regulation of AMPA receptor-mediated transmission being important in withdrawal-induced anxiety and aversion but not in increased seizure sensitivity associated with repeated withdrawal. As changes in AMPA receptor subunit expression alter the functionality of the receptor, future studies will address this possibility.
Assuntos
Encéfalo/efeitos dos fármacos , Diazepam/administração & dosagem , Moduladores GABAérgicos/administração & dosagem , Receptores de AMPA/metabolismo , Síndrome de Abstinência a Substâncias/fisiopatologia , Animais , Autorradiografia/métodos , Encéfalo/anatomia & histologia , Encéfalo/metabolismo , Mapeamento Encefálico , Diazepam/efeitos adversos , Esquema de Medicação , Moduladores GABAérgicos/efeitos adversos , Imidazóis/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Ligação Proteica/efeitos dos fármacos , Quinazolinas/farmacologia , Fatores de Tempo , Distribuição Tecidual/efeitos dos fármacos , Trítio/farmacologiaRESUMO
The acquisition of a conditioned response to a cue associated with a fearful event has been shown to be impaired in animals that had been repeatedly withdrawn from ethanol, but not in animals with the same chronic ethanol treatment but only a single withdrawal episode [D. N. Stephens et al. (2001) Eur. J. Neurosci., 14, 2023-2031]. Lesion studies have shown that the amygdala plays a vital role in this type of conditioning process. Here we investigate aspects of conditioning for appetitive reinforcers in operant tasks, also shown to rely on amygdala processing, in rats following repeated withdrawal from ethanol. Rats were chronically treated with either an ethanol-containing liquid diet for 24 days continuously (single withdrawal) or interspersed with 2 x 3-day withdrawal periods (repeated withdrawal), or with a control diet (control). Two weeks after the final withdrawal, operant training began. In tasks that are impaired by lesions of the basolateral amygdala, conditioned reinforcement and reinforcer devaluation, there was no effect of chronic ethanol treatment or withdrawal on acquisition or performance. However, in a task that is dependent upon functioning of the central nucleus of the amygdala, Pavlovian-to-instrumental transfer, the single and repeated withdrawal groups were significantly impaired. Therefore, chronic ethanol treatment and withdrawal resulted in deficits in behavioural tasks that are sensitive to central but not to basolateral amygdala lesions, and may reflect different sensitivities of these areas to ethanol.
Assuntos
Comportamento Apetitivo/fisiologia , Condicionamento Operante/fisiologia , Etanol/efeitos adversos , Síndrome de Abstinência a Substâncias/psicologia , Tonsila do Cerebelo/fisiologia , Animais , Etanol/administração & dosagem , Masculino , Ratos , Tempo de Reação/fisiologia , Síndrome de Abstinência a Substâncias/fisiopatologiaRESUMO
Repeated withdrawal from ethanol impairs acquisition of conditioned fear [Stephens, D.N., Brown, G., Duka, T. & Ripley, T.L. (2001) Eur. J. Neurosci., 14, 2023-2031]. This study further examined the effect of repeated withdrawal from ethanol on the expression and acquisition of fear conditioning. Following training, presentation of a cue associated with footshock (CS+) resulted in a suppression of operant responding for food reinforcement. In different groups, shock thresholds were manipulated to give weak or severe behavioural suppression. Rats were subsequently chronically treated with ethanol-containing liquid diet either continuously (single withdrawal) or with three withdrawal periods (repeated withdrawal). Ethanol treatment and withdrawal had no effect on conditioned suppression of responding tested 2 weeks after the final withdrawal, at either shock intensity. Nevertheless, extinction of conditioned fear was impaired in the repeated withdrawal group exposed to the higher shock intensity. In the high intensity group, the stimulus-shock association was then reversed, so that the previously neutral conditioned stimulus (CS-) became the CS+. Acquisition of suppression to the new CS+ was significantly less in the animals previously given repeated experience of withdrawal, confirming our previous finding. Thus, repeated withdrawal from ethanol lead to disruption in the acquisition of fear conditioning but had no effect on retrieval of an association formed prior to the ethanol-withdrawal experiences.
Assuntos
Depressores do Sistema Nervoso Central/farmacologia , Condicionamento Psicológico/efeitos dos fármacos , Etanol/farmacologia , Medo/efeitos dos fármacos , Síndrome de Abstinência a Substâncias/fisiopatologia , Animais , Estimulação Elétrica , Extinção Psicológica/efeitos dos fármacos , Masculino , Ratos , Reversão de Aprendizagem/efeitos dos fármacosRESUMO
The ability to manipulate the genetic makeup of organisms by specific targeting of selected genes has provided a novel means of investigating the neurobiological mechanisms underlying drug abuse and dependence. However, as with other techniques, there are a number of potential pitfalls in the use of genetically manipulated animals (usually mice) in behavioural experiments. This review discusses the techniques involved in creating genetically manipulated mice, and points to opportunities and insights into addictive processes provided by the new science, while illustrating some of the potential problems encountered in interpretation of data obtained from such animals. The use of the mouse as an experimental animal also raises some specific problems which limit the usefulness of the technique at present. Examples taken from research into alcohol and psychostimulant abuse and dependence are used to illustrate the usefulness of genetically manipulated animals in addiction research, the problems of interpretation which sometimes arise, and how techniques are being developed to overcome present limitations to this exciting area of research.
Assuntos
Alcoolismo/genética , Alcoolismo/psicologia , Estimulantes do Sistema Nervoso Central , Camundongos Knockout/genética , Camundongos Transgênicos/genética , Transtornos Relacionados ao Uso de Substâncias/genética , Transtornos Relacionados ao Uso de Substâncias/psicologia , Alcoolismo/metabolismo , Animais , Camundongos , Neurotransmissores/biossíntese , Neurotransmissores/genética , Neurotransmissores/metabolismo , Transtornos Relacionados ao Uso de Substâncias/metabolismoRESUMO
Plasminogen activators are serine proteases induced in the brain by electrical activity leading to synaptic remodelling. They are classified into two distinct subtypes, tissue plasminogen activating factor and urokinase plasminogen activating factor (tPA and uPA, respectively), which are both expressed in brain areas thought to be important in learning and memory. Plasminogen activator inhibitor-1 (PAI-1) is the primary inhibitor of tPA and uPA activity, and is expressed in corresponding brain areas. Mice lacking tPA show a deficit in the acquisition of a 15 s differential reinforcement of low rate of responding (DRL15") task relative to their wild types (WTs) under certain conditions. The current set of experiments were designed to investigate further the role of tPA and to extend our knowledge to uPA and PAI-1, using mice with the respective genes deleted (uPA -/- and PAI-1 -/- mice) in the DRL15" task. uPA -/- mice showed no disruption of DRL acquisition, but PAI-1 -/- mice showed a deficit similar to that seen in tPA -/- mice. In an attempt to compensate for this deficit, experiments using a fixed number of reinforcers or a signalled-DRL15" schedule, similar to that used in rat lesion studies of DRL, were performed. tPA -/- mice were able to complete the signalled-DRL task as well as their WTs, and, similarly, PAI-1 -/- mice were able to learn the fixed-number-of-reinforcers-DRL15" schedule and the signalled-DRL schedule. These data indicate that uPA deletion does not affect performance of a standard DRL15" task, whereas deletion of PAI-1 has the same behavioural consequences in these tasks as deletion of tPA. Deficits of both genotypes can be attenuated by providing either external information on completion of the delay or by equalizing the number of reinforcers obtained.
Assuntos
Deleção Cromossômica , Condicionamento Operante/fisiologia , Motivação , Inibidor 1 de Ativador de Plasminogênio/genética , Esquema de Reforço , Ativador de Plasminogênio Tecidual/genética , Ativador de Plasminogênio Tipo Uroquinase/genética , Animais , Comportamento Apetitivo/fisiologia , Feminino , Masculino , Rememoração Mental/fisiologia , Camundongos , Camundongos KnockoutRESUMO
We have previously shown that mice that lack the serine protease, tissue plasminogen activator (tPA), show over-responding on the active lever during time-out periods in an I.V. cocaine self-administration task. To investigate this effect further, tPA knockout mice (tPA-/-) were tested in a number of operant paradigms for a liquid food reinforcer. tPA-/- and wild-type (WT) control mice acquired a fixed ratio (FR) and a fixed interval (FI) task equally. However, extinction from the FR schedule resulted in a significant decrease in responses on the active and inactive levers in the WT mice whilst responding on the inactive lever remained high in the tPA-/- animals. In a differential reinforcement of low rate (DRL) task, tPA-/- mice acquired the task at a slower rate than WT animals. This was characterised by high levels of responding on the active lever during the first 15 sessions in the tPA-/- mice. Burst responding on the active lever (lever press rate with an inter-response time of less than 3 s) was especially high in these animals. This behaviour pattern resulted in the animals obtaining less reinforcers than the WT controls. Acute cocaine dose-dependently shifted the pattern of behaviour on the active lever towards shorter inter-response times. However, there was no difference between the tPA-/- and WT mice in their sensitivity to cocaine on this task. Repeated administration of a low dose of cocaine did not alter performance on this task in either set of animals. When the DRL task was modified to allow the tPA-/- and WT mice an equal number of reinforced trials per session there was no difference in the ability of the animals to perform the task. This would suggest that the tPA-/- mice have a tendency to over-respond but that this can be overcome when the task is modified to allow equal opportunity to learn.
Assuntos
Condicionamento Operante/fisiologia , Fenótipo , Ativador de Plasminogênio Tecidual/genética , Animais , Nível de Alerta/efeitos dos fármacos , Nível de Alerta/genética , Encéfalo/fisiopatologia , Cocaína/administração & dosagem , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Motivação , Esquema de Reforço , AutoadministraçãoRESUMO
Repeated experience of withdrawal from chronic alcohol treatment increases sensitivity to seizures. It has been argued by analogy that negative affective consequences of withdrawal also sensitize, but repeated experience of withdrawal from another sedative-hypnotic drug, diazepam, results in amelioration of withdrawal anxiety and aversiveness. We tested whether giving rats repeated experience of withdrawal from alcohol altered their ability to acquire a conditioned emotional response (CER). Male Hooded Lister rats were fed a nutritionally complete liquid diet as their only food source. Different groups received control diet, or diet containing 7% ethanol. Rats receiving ethanol diet were fed for either 24 days (Single withdrawal, SWD), or 30 days, with two periods of 3 days, starting at day 11, and 21, in which they received control diet (Repeated withdrawal, RWD). All rats were fed lab chow at the end of their liquid diet feeding period. Starting 12 days after the final withdrawal, groups of Control, SWD and RWD rats were given pentylenetetrazole (PTZ; 30 mg/kg, i.p.) three times a week, and scored for seizures. The occurrence of two successive Stage 5 seizures was taken as the criterion for full PTZ kindling. Other groups of control, SWD and RWD rats were trained to operate levers to obtain food, and were then exposed, in a fully counterbalanced design, to light and tone stimuli which predicted unavoidable footshock (CS+), or which had no consequences (CS-). Rats consumed approximately 17.5 g/kg/day of ethanol, resulting in blood alcohol levels of approximately 100 mg/dL. Repeated administration of PTZ resulted in increasing seizure scores. RWD rats achieved kindling criterion faster than either Control or SWD rats. No differences were seen in the groups in flinch threshold to footshock (0.3 mA). At a shock intensity of 0.35 mA, Control, but not RWD or SWD rats showed significant suppression to the CS+ CS- presentation did not affect response rates. The three groups differed in their response to pairing the CS+ with increasing shock levels, the Controls remaining more sensitive to the CS+. SWD rats showed significant suppression of lever pressing during CS+ presentations only at 0.45 and 0.5 mA, and RWD rats only at 0.5 mA. Giving rats repeated experience of withdrawal from chronic ethanol results in increased sensitivity to PTZ kindling, but reduces their ability to acquire a CER. Withdrawal kindling of sensitivity to anxiogenic events does not seem to occur under circumstances which give rise to kindling of seizure sensitivity.
Assuntos
Transtornos do Sistema Nervoso Induzidos por Álcool/complicações , Condicionamento Psicológico/efeitos dos fármacos , Etanol/farmacologia , Medo/efeitos dos fármacos , Excitação Neurológica/efeitos dos fármacos , Convulsões/etiologia , Síndrome de Abstinência a Substâncias/complicações , Estimulação Acústica , Transtornos do Sistema Nervoso Induzidos por Álcool/fisiopatologia , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/fisiologia , Animais , Aprendizagem da Esquiva/efeitos dos fármacos , Aprendizagem da Esquiva/fisiologia , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Condicionamento Psicológico/fisiologia , Esquema de Medicação , Estimulação Elétrica , Medo/fisiologia , Habituação Psicofisiológica/efeitos dos fármacos , Habituação Psicofisiológica/fisiologia , Excitação Neurológica/fisiologia , Masculino , Estimulação Luminosa , Ratos , Ratos Endogâmicos , Convulsões/fisiopatologia , Síndrome de Abstinência a Substâncias/fisiopatologiaRESUMO
Tissue plasminogen activator, tPA, is induced in the brain by electrical activity leading to synaptic remodeling. It is also induced in the prefrontal cortex (PFC) by acute cocaine. We investigated cocaine-induced locomotor activity, the development of sensitisation to cocaine and cocaine self-administration in mice lacking the gene encoding tPA. Mice lacking tPA (tPA knockout mice, tPA-/-) showed normal spontaneous activity, exhibited cocaine-induced locomotor activity at lower doses than wild-type (WT) control mice and showed a greater degree of cocaine-induced locomotor activity following repeated administration. tPA-/- and WT mice did not differ significantly in the time to acquire self-administration of cocaine (20 microg/i.v. infusion) under an FR2 schedule. Following acquisition of this behavior, these groups also did not differ significantly in the rate of cocaine self-administration across the next three sessions. However, WT mice decreased responses on the active lever during signaled periods when reinforcer was not available; in contrast, tPA-/- mice did not. The emission of non-reinforced responses was most marked at the beginning of each 90 min daily session. This pattern of responding was not seen in tPA-/- mice pressing for food under an FR2 schedule of reinforcement. These results suggest that tPA may play a specific role either in retention of information between sessions or in behavioural inhibition in cocaine self-administration.
Assuntos
Química Encefálica/genética , Transtornos Relacionados ao Uso de Cocaína/fisiopatologia , Cocaína/farmacologia , Inibidores da Captação de Dopamina/farmacologia , Ativador de Plasminogênio Tecidual/genética , Animais , Comportamento Animal/efeitos dos fármacos , Condicionamento Psicológico/efeitos dos fármacos , Comportamento Alimentar/efeitos dos fármacos , Injeções Intravenosas , Locomoção/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Plasticidade Neuronal/efeitos dos fármacos , Córtex Pré-Frontal/química , Córtex Pré-Frontal/efeitos dos fármacos , Recompensa , AutoadministraçãoRESUMO
As a great deal of variability between subjects is often seen when using the microdialysis technique to measure the effects of depolarizing agents on extracellular neurotransmitter levels, we have developed a technique to account for the variability inherent in this method. High potassium (50 or 100 mM) artificial cerebrospinal fluid (ACSF), perfused through the probe for 10 min, significantly increased extracellular dopamine (DA) concentration during both an initial and second perfusion, and the two responses were highly correlated. However, extracellular DA returned to normal following the first perfusion with 50 mM K+ but not 100 mM K+ perfusion. The slope of the regression line obtained by plotting the response of the second K+ perfusion as a function of the first K+ perfusion for all K+ concentrations was 1.03 (not significantly different from unity). Similarly, when the time between two 50 mM potassium perfusions was varied from 30-150 min, the responses were highly correlated. This technique was used to demonstrate an interaction between N-methyl-D-aspartate (NMDA) and 50 mM K+. Perfusion of 0.1 mM NMDA alone had no effect on extracellular DA, but NMDA paired with a 50 mM K+ perfusion significantly increased extracellular DA over that increase by 50 mM K+ alone. We propose that a first stimulation with 50 mM potassium may characterize an individual animal's responsiveness to a depolarizing stimulus, and may be used as a control for testing drug effects by coupling drug treatments with a second 50 mM potassium stimulation to give a more accurate measure of small changes in extracellular dopamine.
Assuntos
Corpo Estriado/metabolismo , Dopamina/metabolismo , Potássio/farmacologia , Animais , Cromatografia Líquida de Alta Pressão/métodos , Corpo Estriado/efeitos dos fármacos , Masculino , Microdiálise/métodos , Análise Multivariada , N-Metilaspartato/farmacologia , Perfusão/métodos , Potássio/administração & dosagem , Ratos , Ratos Sprague-Dawley , Análise de Regressão , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Withdrawal hyperexcitability was seen in isolated mouse hippocampal slices, prepared after chronic treatment with ethanol, by inhalation for 2 weeks. The pattern of hyperexcitability differed from those seen previously when a different method of ethanol administration and a different strain of mice were used. Thresholds for field potentials were decreased, but the transient increase in paired pulse potentiation, reported earlier, was not evident. Chronic administration of the calcium channel antagonist, isradipine (PN-200-110) during ethanol treatment significantly decreased the withdrawal syndrome, both in vivo and in vitro. Brain concentrations of isradipine during the test period were found to be sufficient to produce acute effects on the withdrawal hyperexcitability. No changes were seen in the field potentials when slices were prepared after treatment with isradipine alone. A small, but significant, increase in excitability was seen in vivo after the treatment with isradipine alone. Previous studies showed that isradipine did not protect against the hyperexcitability due to gamma-aminobutyric acid (GABA)A antagonism, so the results suggest that neuronal calcium channels may be involved in ethanol withdrawal hyperexcitability, but decreases in GABAA inhibition may not be important.
Assuntos
Delirium por Abstinência Alcoólica/fisiopatologia , Etanol/toxicidade , Hipocampo/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Animais , Bloqueadores dos Canais de Cálcio/farmacocinética , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/efeitos dos fármacos , Canais de Cálcio/fisiologia , Técnicas de Cultura , Relação Dose-Resposta a Droga , Etanol/farmacocinética , Hipocampo/fisiopatologia , Isradipino/farmacocinética , Isradipino/farmacologia , Masculino , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Endogâmicos , Receptores de GABA-A/efeitos dos fármacos , Receptores de GABA-A/fisiologia , Transmissão Sináptica/fisiologiaRESUMO
Hippocampal slices were prepared immediately after withdrawal from chronic ethanol in vivo. The decreases in thresholds for production of single and multiple population spikes seen after the ethanol treatment were not evident when CGP39551 was included in the perfusion medium at 20 microM. The decrease in paired pulse potentiation seen during ethanol withdrawal, however, was not prevented by CGP39551. For comparison, the effects of CGP39551, at the same concentration, were examined on the changes in field potentials seen in control slices when the magnesium concentration in the bathing medium was lowered to 250 microM. The decreases in thresholds for multiple population spikes produced by the lowered magnesium were prevented, but not other changes including decreases in single spike thresholds. In addition, this 20 microM concentration of CGP39551 did not prevent epileptiform activity, measured by decreases in thresholds for production of single and multiple population spikes caused by addition of the GABAA antagonist, bicuculline, to control hippocampal slices.
Assuntos
2-Amino-5-fosfonovalerato/análogos & derivados , Etanol/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Hipocampo/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Relação Dose-Resposta a Droga , Técnicas In Vitro , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Síndrome de Abstinência a Substâncias , Fatores de TempoRESUMO
Prolonged ethanol consumption has previously been reported to decrease long-term potentiation (LTP) in isolated hippocampal slices. Dihydropyridine calcium channel antagonists, such as nitrendipine, have been previously found to prevent some of the adaptive responses to chronic ethanol intake. The present study investigated the effects of concurrent in vivo administration of nitrendipine and ethanol on LTP in isolated mouse hippocampal slices. LTP was produced by either one or two tetanic stimuli or by increased calcium. When one tetanus was used, although the potentiation of the population spike height was less after the ethanol treatment, the difference was not quite significant. However, the potentiation after in vivo administration of ethanol plus nitrendipine was significantly greater than after ethanol alone. When two tetanic stimuli were applied, the maintenance of the potentiation of the population spike height was significantly decreased by the chronic ethanol treatment. This decrease was not seen when nitrendipine was given with the ethanol. When LTP was produced by a transient increase in the calcium concentration in the bathing medium, the chronic ethanol treatment did not alter the potentiation of the population spike height, but in vivo treatment with ethanol plus nitrendipine decreased the potentiation.
Assuntos
Etanol/farmacologia , Hipocampo/efeitos dos fármacos , Potenciação de Longa Duração/efeitos dos fármacos , Nitrendipino/farmacologia , Consumo de Bebidas Alcoólicas , Animais , Cálcio/farmacologia , Eletrofisiologia , Hipocampo/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fatores de TempoRESUMO
The effects of the competitive N-methyl-D-aspartate receptor antagonist DL-(E)-2-amino-4-methyl-5-phosphonopentanoate carboxy-ethylester (CGP39551) on the hyperexcitability produced by withdrawal from chronic ethanol treatment were studied in mice, to which CGP39551 was given chronically with the ethanol. When an interval of 72 or 96 hr was left between the last of the repeated CGP39551 injections and withdrawal from ethanol, the severity of the ethanol withdrawal syndrome was increased. When shorter time intervals were left between the end of the CGP39551 treatment and the ethanol withdrawal, the chronic CGP39551 treatment protected against the withdrawal hyperexcitability. When a single low dose of CGP39551 was given immediately after ethanol withdrawal, the compound protected against the withdrawal hyperexcitability. It is therefore suggested that the protective effects of concurrent chronic treatment with CGP39551, seen when the shorter intervals were allowed, were caused by residual compound. The increased severity of withdrawal, when sufficient time was left for washout of CGP39551, suggests that chronic administration of CGP39551 increased the adaptive changes that cause or contribute to ethanol withdrawal hyperexcitability. The results differ from the previously reported effects of N-methyl-D-aspartate antagonists on ethanol tolerance, because this was reduced by concurrent chronic treatment. They are also in contrast with the effects of chronic dihydropyridine calcium channel antagonists, which decreased both the development of tolerance and the ethanol withdrawal syndrome, when given chronically, concurrently with the ethanol. Cessation of prolonged ethanol intake results in a period of neuronal hyperexcitability, described as the withdrawal or abstinence syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
2-Amino-5-fosfonovalerato/análogos & derivados , Etanol/efeitos adversos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Síndrome de Abstinência a Substâncias/fisiopatologia , 2-Amino-5-fosfonovalerato/administração & dosagem , Animais , Esquema de Medicação , Manobra Psicológica , Masculino , Camundongos , Camundongos Endogâmicos , Convulsões/induzido quimicamente , Fatores de TempoRESUMO
A complex pattern of changes in the field potentials recorded from mouse hippocampal slices, prepared after chronic ethanol treatment in vivo, has previously been demonstrated in this laboratory. In the present study, recordings from slices prepared immediately after 2 weeks of ethanol treatment, showed only an increase in paired pulse potentiation, compared with controls, whereas recordings made immediately after 16 weeks of ethanol administration showed decreases in the thresholds for single and multiple population spikes, increases in paired pulse potentiation and epileptiform activity. In hippocampal slices prepared after 24 hr withdrawal, following 16 weeks of ethanol treatment, there were no signs of hyperexcitability in the field potentials. Ratings of convulsive behaviour were increased in mice during a 12-hr period after withdrawal from 16 weeks of ethanol treatment. Corresponding behaviour ratings for the mice given ethanol for 2 weeks, or those withdrawn for 24 hr after 16 weeks ethanol treatment, were not significantly different from control values. It was concluded that epileptiform activity seen in hippocampal slices after prolonged ethanol administration may contribute to the ethanol withdrawal hyperexcitability seen in vivo.
Assuntos
Delirium por Abstinência Alcoólica/fisiopatologia , Alcoolismo/fisiopatologia , Etanol/toxicidade , Hipocampo/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Animais , Nível de Alerta/efeitos dos fármacos , Nível de Alerta/fisiologia , Técnicas de Cultura , Eletroencefalografia/efeitos dos fármacos , Hipocampo/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Transmissão Sináptica/fisiologiaRESUMO
The effects of the imidazoline 6,7-benzoidazoxan on seizure threshold were assessed using standard tests of anticonvulsant activity. Benzoidazoxan (10-30 mg/kg i.p.; 100 mg/kg p.o.) prevented tonic, but not clonic, convulsions induced by electroshock in mice. The increase in seizure threshold was of rapid onset, and, although of short duration, was comparable with that obtained using phenytoin and sodium valproate. Moreover, unlike sodium valproate, benzoidazoxan was an efficacious anticonvulsant at doses (20, 30 mg/kg i.p.) which did not impair rotarod performance. The anticonvulsant effects of benzoidazoxan were confirmed using the maximal electroshock test in mice (median effective dose, 13.2 mg/kg i.p.) and rats (anticonvulsant at 30 mg/kg i.p.). In addition, benzoidazoxan (10, 30 mg/kg i.p.) prevented tonic, but not clonic, seizures induced by bicuculline in mice. Thus, the imidazoline benzoidazoxan was found to be a novel anticonvulsant agent against electrically and chemically induced seizures in mice and rats with a profile of action similar to that of phenytoin.