RESUMO
Impaired responsivity to hypercapnia or hypoxia is commonly considered a mechanism of failure in sudden infant death syndrome (SIDS). The search for deficient brain structures mediating flawed chemosensitivity typically focuses on medullary regions; however, a network that includes Purkinje cells of the cerebellar cortex and its associated cerebellar nuclei also helps mediate responses to carbon dioxide (CO2) and oxygen (O2) challenges and assists integration of cardiovascular and respiratory interactions. Although cerebellar nuclei contributions to chemoreceptor challenges in adult models are well described, Purkinje cell roles in developing models are unclear. We used a model of developmental cerebellar Purkinje cell loss to determine if such loss influenced compensatory ventilatory responses to hypercapnic and hypoxic challenges. Twenty-four Lurcher mutant mice and wild-type controls were sequentially exposed to 2% increases in CO2 (0-8%) or 2% reductions in O2 (21-13%) over 4 min, with return to room air (21% O2/79% N2/0% CO2) between each exposure. Whole body plethysmography was used to continuously monitor tidal volume (TV) and breath frequency (f). Increased f to hypercapnia was significantly lower in mutants, slower to initiate, and markedly lower in compensatory periods, except for very high (8%) CO2 levels. The magnitude of TV changes to increasing CO2 appeared smaller in mutants but only approached significance. Smaller but significant differences emerged in response to hypoxia, with mutants showing smaller TV when initially exposed to reduced O2 and lower f following exposure to 17% O2. Since cerebellar neuropathology appears in SIDS victims, developmental cerebellar neuropathology may contribute to SIDS vulnerability.
Assuntos
Cerebelo/crescimento & desenvolvimento , Cerebelo/fisiopatologia , Hipercapnia/fisiopatologia , Hipóxia/fisiopatologia , Células de Purkinje/fisiologia , Receptores de Glutamato/metabolismo , Animais , Modelos Animais de Doenças , Humanos , Lactente , Masculino , Camundongos Mutantes Neurológicos , Pletismografia Total , Receptores de Glutamato/genética , Respiração , Morte Súbita do Lactente , Volume de Ventilação Pulmonar/fisiologiaRESUMO
Some, but not all, rats eat or drink in response to electrical stimulation of the lateral hypothalamus. Similarly, some, but not all, rats given food intermittently display schedule-induced polydipsia. In this experiment, animals that ate or drank during electrical stimulation tended also to be those displaying polydipsia. Thus, individual differences in predisposition to engage in ingestive behavior are consistent under two very different conditions.
Assuntos
Comportamento de Ingestão de Líquido/fisiologia , Comportamento Alimentar/fisiologia , Hipotálamo/fisiologia , Sede/fisiologia , Animais , Estimulação Elétrica , Masculino , RatosRESUMO
Cognitive flexibility has traditionally been considered a frontal lobe function. However, converging evidence suggests involvement of a larger brain circuit which includes the cerebellum. Reciprocal pathways connecting the cerebellum to the prefrontal cortex provide a biological substrate through which the cerebellum may modulate higher cognitive functions, and it has been observed that cognitive inflexibility and cerebellar pathology co-occur in psychiatric disorders (e.g., autism, schizophrenia, addiction). However, the degree to which the cerebellum contributes to distinct forms of cognitive flexibility and rule learning is unknown. We tested lurcherâwildtype aggregation chimeras which lose 0-100% of cerebellar Purkinje cells during development on a touchscreen-mediated attentional set-shifting task to assess the contribution of the cerebellum to higher and lower order rule learning and cognitive flexibility. Purkinje cells, the sole output of the cerebellar cortex, ranged from 0 to 108,390 in tested mice. Reversal learning and extradimensional set-shifting were impaired in mice with⩾95% Purkinje cell loss. Cognitive deficits were unrelated to motor deficits in ataxic mice. Acquisition of a simple visual discrimination and an attentional-set were unrelated to Purkinje cells. A positive relationship was observed between Purkinje cells and errors when exemplars from a novel, non-relevant dimension were introduced. Collectively, these data suggest that the cerebellum contributes to higher order cognitive flexibility, lower order cognitive flexibility, and attention to novel stimuli, but not the acquisition of higher and lower order rules. These data indicate that the cerebellar pathology observed in psychiatric disorders may underlie deficits involving cognitive flexibility and attention to novel stimuli.
Assuntos
Cerebelo/fisiologia , Função Executiva/fisiologia , Reversão de Aprendizagem/fisiologia , Análise de Variância , Animais , Ataxia/patologia , Ataxia/fisiopatologia , Atenção/fisiologia , Cerebelo/patologia , Cerebelo/fisiopatologia , Quimera , Cognição , Transtornos Cognitivos/patologia , Transtornos Cognitivos/fisiopatologia , Camundongos Mutantes Neurológicos , Testes Neuropsicológicos , Tempo de Reação , RecompensaRESUMO
Understanding how alcohol exposure during adolescence affects aging is a critical but understudied area. In the present study, male rats were exposed to either alcohol or saline during adolescence, then tested every 4 months following either an ethanol or saline challenge; animals were tested until postnatal day (PD) 532. It was found that long-lasting tolerance to high-dose ethanol exists through the test period, as measured by loss of righting reflex, while tolerance to lower doses of ethanol is not found. In addition, alcohol exposure during adolescence facilitated spatial memory impairments to acute ethanol challenges later in life. The current work demonstrates that exposure to ethanol during adolescent development can produce long-lasting detrimental impairments.
Assuntos
Tolerância a Medicamentos/fisiologia , Etanol/administração & dosagem , Transtornos da Memória/induzido quimicamente , Memória Espacial/efeitos dos fármacos , Consumo de Álcool por Menores , Adolescente , Animais , Relação Dose-Resposta a Droga , Humanos , Masculino , Ratos , Ratos Sprague-Dawley , Reflexo de Endireitamento/efeitos dos fármacos , Reflexo de Endireitamento/fisiologiaRESUMO
New emphasis has been placed upon cerebellar research because of recent reports demonstrating involvement of the cerebellum in non-motor cognitive behaviors. Included in the growing list of cognitive functions associated with cerebellar activation is working memory. In this study, we explore the potential role of the cerebellum in spatial working memory using a mouse model of Purkinje cell loss. Specifically, we make aggregation chimeras between heterozygous lurcher (Lc/+) mutant embryos and +/+ (wildtype) embryos and tested them in the delayed matching-to-position (DMTP) task. Lc/+ mice lose 100% of their Purkinje cells postnatally due to a cell-intrinsic gain-of-function mutation. Lc/+<->+/+ chimeras therefore have Purkinje cells ranging from 0 to normal numbers. Through histological examination of chimeric mice and observations of motor ability, we showed that ataxia is dependent upon both the number and distribution of Purkinje cells in the cerebellum. In addition, we found that Lc/+ mice, with a complete loss of Purkinje cells, have a generalized deficit in DMTP performance that is probably associated with their motor impairment. Finally, we found that Lc/+<->+/+ chimeric mice, as a group, did not differ from control mice in this task. Rather, surprisingly, analysis of their total Purkinje cells and performance in the DMTP task revealed a significant negative relationship between these two variables. Together, these findings indicate that the cerebellum plays a minor or indirect role in spatial working memory.
Assuntos
Cerebelo/anormalidades , Quimera/fisiologia , Memória de Curto Prazo/fisiologia , Malformações do Sistema Nervoso/fisiopatologia , Células de Purkinje/fisiologia , Comportamento Espacial/fisiologia , Animais , Ataxia/genética , Ataxia/fisiopatologia , Contagem de Células , Morte Celular/genética , Cerebelo/patologia , Quimera/genética , Comportamento de Escolha/fisiologia , Camundongos , Camundongos Mutantes Neurológicos , Mutação/genética , Malformações do Sistema Nervoso/patologia , Testes Neuropsicológicos , Células de Purkinje/patologiaRESUMO
Mature rats were given lesions of the hippocampus (HIPPO), subiculum (SUBIC) or fimbria-fornix (FIFO) and then received the mild chronic stressors of food deprivation and isolation housing for ten months prior to testing. Group differences in circadian activity were investigated along with locomotion elicited by amphetamine (AMP 1.0-2.0 mg/kg i.p.) alone, and following the corticosterone (CORT) synthesis inhibitor, metyrapone (MET 10.0-25.0 mg/kg i.p.). Basal levels of plasma CORT, (ng/ml), plasma glucose (GLUC, mmol/l), thymic and splenic wet weights were subsequently determined along with complete blood counts (CBC). In comparison to age matched, unoperated controls, selective SUBIC lesions altered the circadian periodicity of locomotion, while rats with FIFO lesions were spontaneously hyperactive. Both HIPPO and FIFO animals showed significantly higher levels of amphetamine-induced locomotion. In all groups metyrapone significantly enhanced locomotion elicited by amphetamine, probably due to a pharmacokinetic interaction between these drugs. In comparison to controls, animals in the HIPPO group showed significant reductions in plasma glucose levels, decreased thymic wet weights and reductions in lymphocyte numbers, indicating lesion-related immuno-suppression. These findings highlight a functional difference among the effects of these specific hippocampal lesions on neural regulation of the HPA axis, under conditions of chronic mild stress, suggesting that the modulatory influence of the hippocampus on the stress axis is dependent on the neuroanatomical location and total extent of cell loss within this structure. They further suggest that the heightened response to amphetamine occurs independently of any lesion-induced changes in modulation of the HPA axis.
Assuntos
Nível de Alerta/fisiologia , Glicemia/metabolismo , Corticosterona/sangue , Hipocampo/fisiopatologia , Sistema Hipotálamo-Hipofisário/fisiopatologia , Tolerância Imunológica/fisiologia , Atividade Motora/fisiologia , Sistema Hipófise-Suprarrenal/fisiopatologia , Estresse Psicológico/complicações , Animais , Ritmo Circadiano/fisiologia , Fórnice/patologia , Fórnice/fisiologia , Hipocampo/patologia , Sistema Hipotálamo-Hipofisário/patologia , Contagem de Linfócitos , Masculino , Sistema Hipófise-Suprarrenal/patologia , Ratos , Ratos Long-Evans , Baço/patologia , Timo/patologiaRESUMO
Two experiments investigated the effects of ibotenic-acid lesions of the hippocampus on food-rewarded performance under a progressive-ratio 10 schedule of reinforcement. The results of Experiment 1 indicated that rats with hippocampal lesions showed profound increases in breakpoint and enhancements in the efficiency of responding. In a second experiment the same rats were challenged with prefeeding, increases in the height of the response lever, and the substitution of sucrose- for grain-based reward pellets. Responding in both groups was similarly reduced by prefeeding and increases in the effortfulness of responding, but lesioned rats were significantly more responsive to the change to sucrose reward. Overall, the results indicated that hippocampal damage increased responding by enhancing the activational or hedonic properties of the delivered food pellets, while not affecting food-motivation or the motor capacity to respond.
Assuntos
Comportamento Apetitivo/fisiologia , Hipocampo/fisiologia , Motivação , Esquema de Reforço , Tonsila do Cerebelo/fisiologia , Animais , Mapeamento Encefálico , Corpo Estriado/fisiologia , Dopamina/fisiologia , Feminino , Ácido Ibotênico , Sistema Límbico/fisiologia , Masculino , Mesencéfalo/fisiologia , Vias Neurais/fisiologia , Núcleo Accumbens/fisiologia , Desempenho Psicomotor/fisiologia , Ratos , Paladar/fisiologiaRESUMO
Five experiments investigated in rats the effects of increasing or decreasing plasma corticosterone levels on schedule-induced polydipsia and dopamine efflux in the nucleus accumbens. The results indicate that the acquisition of schedule-induced polydipsia could be decreased by adrenalectomy, blockade of corticosterone synthesis, or administration of corticosterone. Performance of established schedule-induced polydipsia was also decreased by adrenalectomy. The effects of corticosterone administration on established schedule-induced polydipsia depended on the level of performance. High levels of drinking were enhanced by a high dose of corticosterone, whereas low rates of drinking were increased by a low dose. Similar injections of corticosterone also significantly increased dopamine efflux. The relative involvement of pituitary-adrenal activity and dopamine neurotransmission in the nucleus accumbens in the acquisition and performance of SIP is discussed and related to contemporary hypotheses of schedule-induced behavior.
Assuntos
Dopamina/fisiologia , Comportamento de Ingestão de Líquido/fisiologia , Núcleo Accumbens/fisiologia , Sistema Hipófise-Suprarrenal/fisiologia , Receptores Dopaminérgicos/fisiologia , Esquema de Reforço , Animais , Nível de Alerta/fisiologia , Condicionamento Clássico/fisiologia , Corticosterona/fisiologia , Masculino , Ratos , Comportamento Estereotipado/fisiologiaRESUMO
Previous research has shown that animals predisposed to eat and drink in response to electrical stimulation of the lateral hypothalamus (ESLH) are similarly predisposed to drink excessively when tested for schedule-induced polydipsia. The eating and drinking elicited by both experimental paradigms appears to be unrelated to homeostatic need and has been called nonregulatory ingestive behavior. In this study, the relation between properties of dopaminergic neural systems and the predisposition to exhibit nonregulatory ingestive behavior was investigated. It was found that rats that eat and drink during ESLH show greater behavioral sensitization to a series of amphetamine injections that those that do not exhibit ingestive behavior during ESLH. In addition, footshock stress produced a greater increase in forebrain dopamine utilization in rats that engaged in nonregulatory ingestive behavior. This evidence is consistent with the hypothesis that there are individual differences in the responsiveness of forebrain dopamine systems that are related to the behavioral predisposition to exhibit nonregulatory ingestive behavior.
Assuntos
Encéfalo/fisiologia , Dopamina/fisiologia , Comportamento de Ingestão de Líquido/fisiologia , Comportamento Alimentar/fisiologia , Animais , Corpo Estriado/metabolismo , Dextroanfetamina/farmacologia , Região Hipotalâmica Lateral/fisiologia , Individualidade , Masculino , Núcleo Accumbens/metabolismo , Ratos , Esquema de Reforço , Comportamento Estereotipado/efeitos dos fármacosRESUMO
The sequential occurrence of licking, locomotor activity, entries into the food magazine (panel pressing), and nonreenforced lever pressing engendered by a periodic schedule of food presentation were measured in each 60-s interreenforcement interval in normal and brain-damaged rats. The development of these responses was measured over 20 days in different groups of food-deprived rats that had received aspirations of the hippocampus, small lesions of the cortex overlying the hippocampus (hippocampal-operated control group), decortication, or 6-hydroxy-dopamine lesions of the caudate nucleus or nucleus accumbens. All lesions produced distinctive patterns of change in the measured behaviors, and dissociations as well as similarities in their effects were evident. These results are discussed with respect to dissociations in the motor and motivational effects of the various lesions and in terms of contemporary hypotheses of schedule-induced behavior.
Assuntos
Comportamento Apetitivo/fisiologia , Córtex Cerebral/fisiologia , Ritmo Circadiano/fisiologia , Corpo Estriado/fisiologia , Hipocampo/fisiologia , Esquema de Reforço , Animais , Nível de Alerta/fisiologia , Mapeamento Encefálico , Núcleo Caudado/fisiologia , Dopamina/fisiologia , Comportamento de Ingestão de Líquido/fisiologia , Comportamento Alimentar/fisiologia , Masculino , Atividade Motora/fisiologia , Vias Neurais/fisiologia , Núcleo Accumbens/fisiologia , Ratos , Ratos Endogâmicos , Tempo de Reação/fisiologiaRESUMO
RATIONALE: It has been suggested that GABA(B) receptors may be part of a neural substrate mediating some of the effects of ethanol. OBJECTIVE: The purpose of this experiment was to investigate, in mice, the effects of ethanol on working memory in a delayed matching-to position (DMTP) task, and additionally to determine if these effects were modulated by GABA(B) receptors. METHODS: Female C57BL/6J and DBA/2J mice were trained in the DMTP task, and after asymptotic levels of performance accuracy were achieved, injections (IP) of ethanol, baclofen, or phaclofen were administered. Baclofen or phaclofen were then co-administered with ethanol. Each test was repeated twice. RESULTS: Ethanol caused deficits in working memory at 2.0 g/kg and higher. The highest dose (2.5 g/kg) produced additional non-specific effects, indicative of sedation. Baclofen increased performance accuracy (2.5 mg/kg), while decreasing the total number of trials completed. When combined with ethanol (1.5 g/kg), baclofen increased memory deficits at the highest dose (7.5 mg/kg). Phaclofen increased performance accuracy at 10 and 30 mg/kg but had no effect on the total number of trials completed. When combined with ethanol (2.5 g/kg), phaclofen did not significantly alter ethanol-induced deficits in performance. CONCLUSIONS: Analyses of performance accuracy, total trials completed and variables indexing bias and motor impairment indicated that GABA(B) drugs modulate working memory in a behaviorally specific manner. Overall, these receptors may be part of a neural substrate that modulates some of the effects of ethanol.
Assuntos
Baclofeno/análogos & derivados , Etanol/farmacologia , Agonistas dos Receptores de GABA-B , Antagonistas de Receptores de GABA-B , Memória/efeitos dos fármacos , Animais , Baclofeno/farmacologia , Relação Dose-Resposta a Droga , Combinação de Medicamentos , Feminino , Memória/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Receptores de GABA-B/fisiologia , Especificidade da EspécieRESUMO
This experiment investigated the possibility that rats maintained on chronic haloperidol treatment would show increased behavioral responsiveness to cocaine, similar to that observed in human stimulant abusers who are chronically treated with neuroleptics. Thus, the effects on locomotion and stereotyped behavior of intermittent injections of cocaine were investigated in female rats receiving chronic haloperidol treatment. Daily injections of haloperidol (0.2 mg/kg, IP) or vehicle were administered for 6, 12 or 18 days prior to the start of testing with cocaine and were then continued throughout cocaine testing. All rats received four doses of cocaine (0.0, 3.0, 7.5, or 15.0 mg/kg, IP) in random order with an intervening vehicle day between successive drug days. The four dose sequence of cocaine was repeated a total of four times. Initial cocaine administration produced dose dependent increases in locomotion and stereotyped behavior. When the sequence of cocaine doses was repeated, differences among treatment groups emerged. Groups treated with haloperidol exhibited heightened locomotion in response to cocaine and with repeated injections, showed a higher rate of behavioral sensitization than control animals. These differences in the behavioral response to cocaine were maintained for at least 2 months following termination of daily haloperidol treatment. In order to examine the mechanisms underlying this heightened responsiveness to cocaine, apomorphine-induced locomotion (dose range, 0-250 micrograms/kg, SC) was determined. Regardless of dose, rats treated with haloperidol showed different temporal patterns of locomotion in response to apomorphine suggesting that the increased response to cocaine was related to changes in dopaminergic receptor sensitivity.
Assuntos
Comportamento Animal/efeitos dos fármacos , Cocaína , Haloperidol/farmacologia , Transtornos Relacionados ao Uso de Substâncias/psicologia , Animais , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Interações Medicamentosas , Feminino , Atividade Motora/efeitos dos fármacos , Ratos , Receptores Pré-Sinápticos/efeitos dos fármacos , Comportamento Estereotipado/efeitos dos fármacosRESUMO
The authors selected articles from those published between 1975 and 1994 that specifically documented psychostimulant abuse in patients determined to be schizophrenic according to recent and relatively uniform diagnostic criteria. These articles indicated that the incidence of psychostimulant abuse in schizophrenics is 2-5 times higher than that of the general public. Additionally, unlike the decline in stimulant use seen in older adults in the general population, high rates of abuse appeared to be maintained in schizophrenics. Although the incidence of abuse in this group was high, comparisons of abuse rates generated by self report with those obtained by urinalysis indicated that the frequency of abuse is being underestimated by 15-21%. Potential factors contributing to stimulant abuse in schizophrenics, including the disease process, and the influence of chronic neuroleptic medication, were evaluated. Results indicated that the incidence of psychostimulant abuse was neither a common property of psychiatric patients, nor exclusive to schizophrenics, but appeared to be related to chronic treatment with neuroleptic drugs. Symptom severity was generally similar in schizophrenic abusers and non-abusers, which also suggested a degree of independence from the disease process. In a majority of the studies surveyed, abuse of stimulants followed disease onset. It was also found that stimulant abuse was associated with marked increases in hospitalization in this patient group, including those known to be neuroleptic medication compliant. Possible explanations for the initiation and maintenance of psychostimulant abuse in schizophrenics are discussed in relation to clinical and preclinical evidence on drug addiction.
Assuntos
Psicotrópicos/farmacologia , Esquizofrenia/fisiopatologia , Transtornos Relacionados ao Uso de Substâncias , Humanos , Psicologia do EsquizofrênicoRESUMO
Although benzodiazepine agonists and inverse agonists have opposite effects on drinking elicited by water deprivation, there is much less information about the effects of these drugs on nonhomeostatic drinking. In this experiment the effects of diazepam (0.3-5.0 mg/kg), a benzodiazepine receptor agonist, and FG 7142 (1.0-9.0 mg/kg), an inverse agonist, were determined on drinking elicited by a FT-60 schedule of food delivery (SIP). Both diazepam and FG 7142 dose-dependently reduced SIP, measured as either licking or volume consumed. In addition, diazepam reduced panel pressing for food, decreased locomotor activity, and changed the time course of each behavior. In contrast, FG 7142 reduced schedule-induced drinking without significantly altering other behaviors. The antagonist RO 15-1788, when given in combination with these drugs, only partially restored the reductions in licking produced by diazepam, but was much more effective in reversing the effects of FG 7142 at doses of the antagonist that failed by themselves to affect responding. The opposite pattern of effects was seen on the volume of water consumed. These effects are discussed in terms of the behavioral and pharmacological specificity of these drugs.
Assuntos
Depressores do Apetite/farmacologia , Carbolinas/farmacologia , Diazepam/farmacologia , Comportamento de Ingestão de Líquido/efeitos dos fármacos , Flumazenil/farmacologia , Animais , Diazepam/antagonistas & inibidores , Masculino , Atividade Motora/efeitos dos fármacos , RatosRESUMO
Covert attention to visuospatial stimuli was assessed in rats using a modified version of a task designed for human subjects. Rats were trained to respond toward bright target lights presented to the right or left visual space. Dim cue lights served to attract their attention prior to the onset of the bright target lights. Consistent with previous research using similar paradigms, rats in this experiment displayed longer reaction times during trials in which the cue and target lights were presented on opposite sides of visual space. Throughout pre- and post-operative testing, individual subjects showed lateralized differences in the performance of this task as indicated by asymmetries in reaction time, the percentage of correct responses, and the number of responses made to each side of visual space (response bias). Lesioning the area of cortex thought to be a possible homolog of the posterior parietal cortex in primates produced no specific effects on performance. It is suggested that this paradigm may tap into an evolutionarily conserved attentional process, but that this process may be subserved by somewhat different neural structures in different species.
Assuntos
Atenção/fisiologia , Lobo Parietal/fisiologia , Percepção Espacial/fisiologia , Percepção Visual/fisiologia , Animais , Condicionamento Operante/fisiologia , Sinais (Psicologia) , Dominância Cerebral/fisiologia , Feminino , Lateralidade Funcional/fisiologia , Lobo Parietal/lesões , Estimulação Luminosa , Ratos , Tempo de Reação/fisiologiaRESUMO
The main purpose of this study was to explore the role of the hippocampus in motivated behavior. Rats with bilateral excitotoxic lesions of the hippocampus and controls were trained to lever press for electrical stimulation of the ventral tegmental area. Rate intensity functions were generated from an ascending and descending series of current intensities. Lesion-induced changes in sensitivity to reward were distinguished from enhancements in motor output by calculating reward thresholds and maximal response rates from the rate-intensity functions. Rats with hippocampal damage showed lower reward thresholds and higher maximal response rates than controls. These results provide further evidence of hippocampal modulation of the nucleus accumbens, suggesting that lesions of this structure enhance sensitivity to reward and increase motor output.
Assuntos
Hipocampo/fisiologia , Recompensa , Autoestimulação/fisiologia , Área Tegmentar Ventral/fisiologia , Animais , Química Encefálica/fisiologia , Dopamina/metabolismo , Dopamina/fisiologia , Estimulação Elétrica , Eletrodos Implantados , Hipocampo/anatomia & histologia , Hipocampo/lesões , Masculino , Motivação , Desempenho Psicomotor/fisiologia , Ratos , Ratos Long-EvansRESUMO
The relationship between schedule-induced polydipsia (SIP) and pituitary-adrenal activity in rats was investigated using two different approaches that involved either capitalizing on pre-existing individual differences in the propensity to show SIP, or by inducing differences in plasma corticosterone by behavioral or pharmacological means. Thus, in Expt. 1, SIP was monitored after corticosterone levels were pharmacologically altered with drugs that act at the benzodiazepine receptor. In Expt. 2, the relationship between individual differences in water consumption during SIP and plasma corticosterone levels was determined. In addition, corticosterone levels were determined after the prevention of drinking during SIP. Results indicated an inverse relationship between plasma corticosterone levels and SIP. It was also found that corticosterone levels were significantly higher following SIP with water available than after SIP without water. The implications of these results for previous hypotheses of SIP are discussed.
Assuntos
Comportamento Apetitivo/efeitos dos fármacos , Carbolinas/farmacologia , Corticosterona/sangue , Diazepam/farmacologia , Ingestão de Líquidos/efeitos dos fármacos , Sistema Hipófise-Suprarrenal/efeitos dos fármacos , Animais , Nível de Alerta/efeitos dos fármacos , Relação Dose-Resposta a Droga , Masculino , Ratos , Ratos Endogâmicos , Receptores de GABA-A/efeitos dos fármacos , Esquema de ReforçoRESUMO
Rats were trained to orient to a visual cue presented in either visual field. An asymmetry in reaction time showed that they used one eye to control responses to both visual fields. Cortical removal contralateral to this dominant eye produced a severe and permanent response deficit. Cortical removal ipsilateral to the dominant eye caused a mild and temporary change. Thus, in the rat, there is a functional lateralization that is similar to that seen in humans.
Assuntos
Córtex Cerebral/fisiologia , Dominância Cerebral/fisiologia , Tempo de Reação/fisiologia , Percepção Visual/fisiologia , Animais , Nível de Alerta/fisiologia , Atenção/fisiologia , Mapeamento Encefálico , Masculino , Desempenho Psicomotor/fisiologia , Ratos , Ratos Endogâmicos , Privação Sensorial/fisiologia , Vias Visuais/fisiologiaRESUMO
The present experiment investigated the effects of unilateral 6-hydroxydopamine lesions of the caudate nucleus and nucleus accumbens on eating and drinking evoked by electrical stimulation of the lateral hypothalamus (ESLH). Lesions were made on either the 'dominant' or 'non-dominant' hemisphere as defined by an amphetamine-rotation test. We report here that lesions of the 'dominant hemisphere' were significantly more effective in disrupting ESLH-evoked behavior as well as producing longer-lasting deficits in somatosensory responsiveness as measured by the 'tactile extinction test'.
Assuntos
Dopamina/fisiologia , Comportamento de Ingestão de Líquido/fisiologia , Comportamento Alimentar/fisiologia , Região Hipotalâmica Lateral/fisiologia , Animais , Mapeamento Encefálico , Núcleo Caudado/fisiologia , Estimulação Elétrica , Hidroxidopaminas/farmacologia , Masculino , Núcleo Accumbens/fisiologia , Oxidopamina , RatosRESUMO
Rats with limbic system damage display increases in responsivity to sensory stimulation and changes in the sensitivity to amphetamine, suggesting that their condition may parallel that of human schizophrenia. This experiment examined locomotion and stereotyped behavior in mature, male rats that had received aspirative lesions of the hippocampus, control lesions of the overlying parietal cortex, or were unoperated controls. Locomotion, measured as photocell beam breaks, was recorded during 2- or 3-h test sessions. Behavioral stereotypy was simultaneously rated. Hippocampal lesioned rats exhibited a selective enhancement in locomotion following D-amphetamine (0.0-5.6 mg/kg) when compared to animals in the control groups. Similar results were observed following injections of apomorphine (0.0-0.25 mg/kg), a mixed D1 and D2 agonist. In order to determine if D1 or D2 receptors were involved in this increased locomotion, the D1 agonist SKF 38393 (0.0-15 mg/kg) and the D2 agonist quinpirole (0.0-0.5 mg/kg) were tested alone and in combination. Hippocampal-ablated rats showed significantly increased locomotion only in response to quinpirole, suggesting that these lesion-induced increases were largely mediated by D2 receptors. When both drugs were administered together, SKF 38393 further enhanced the locomotor stimulating effects of quinpirole in hippocampal lesioned rats, indicating a synergistic interaction between D1 and D2 receptors in the modulation of locomotion. These findings provide further evidence of hippocampal modulation of locomotion and suggest that dopaminergic mechanisms in the nucleus accumbens, probably involving changes in receptor sensitivity, are involved. The results are discussed in relation to the functional roles of the nucleus accumbens and in terms of their implications for mental diseases including schizophrenia.