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BACKGROUND: N-methyl-d-aspartate (NMDA) receptor hypofunction has been implicated in the pathophysiology of schizophrenia and its associated neurocognitive impairments. The high rate of cigarette smoking in schizophrenia raises questions about how nicotine modulates putative NMDA receptor hypofunction in the illness. Accordingly, we examined the modulatory effects of brain nicotinic acetylcholine receptor (nAChR) stimulation on NMDA receptor hypofunction by examining the interactive effects of nicotine, a nAChR agonist, and ketamine, a non-competitive NMDA receptor antagonist, on behavioral and neurophysiological measures in healthy human volunteers. METHODS: From an initial sample of 17 subjects (age range 18-55 years), 8 subjects successfully completed 4 test sessions, each separated by at least 3 days, during which they received ketamine or placebo and two injections of nicotine or placebo in a double-blind, counterbalanced manner. Schizophrenia-like effects Positive and Negative Syndrome Scale, perceptual alterations Clinician Administered Dissociative Symptoms Scale, subjective effects Visual Analog Scale and auditory event-related brain potentials (mismatch negativity, MMN; P300) were assessed during each test session. RESULTS: Consistent with existing studies, ketamine induced transient schizophrenia-like behavioral effects. P300 was reduced and delayed by ketamine regardless of whether it was elicited by a target (P3b) or novel (P3a) stimulus, while nicotine only reduced the amplitude of P3a. Nicotine did not rescue P300 from the effects of ketamine; the interactions of ketamine and nicotine were not significant. While nicotine significantly reduced MMN amplitude, ketamine did not. CONCLUSION: Nicotine failed to modulate ketamine-induced neurophysiological and behavioral effects in this preliminary study. Interestingly, ketamine reduced P3b amplitude and nicotine reduced P3a amplitude, suggesting independent roles of NMDA receptor and nAChR in the generation of P3b and P3a, respectively.
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INTRODUCTION: There are mixed reports on nicotine's effects on alcohol-induced impairment in cognitive performance and behavior in humans. The main objective of this study was to characterize the interactive effects of acute intravenous (IV) alcohol and nicotine administration on behavior and cognition in healthy nonsmokers. METHODS: Healthy subjects aged 21-44 years participated in 3 test days. On each test day, they received in a double-blind randomized manner one of three IV alcohol infusion conditions using a "clamp": placebo, targeted breathalyzer of 40 mg%, or targeted breathalyzer of 80 mg%. Alcohol infusion was delivered over 20 min and lasted for 120 min. They also received both placebo and active nicotine in a fixed order delivered intravenously. Placebo nicotine was delivered first over 10 min at the timepoint when the breath alcohol was "clamped"; active nicotine (1.0 mcg/kg/min) was delivered for 10 min, 70 min after the alcohol infusion was clamped. Subjective effects of alcohol were measured using the Biphasic Alcohol Effects Scale and the Number of Drinks Scale. Cognitive inhibition and attention were measured by the Continuous Performance Task-Identical Pairs and working memory by the Rey Auditory Verbal Learning Task (RAVLT). RESULTS: Nicotine significantly reversed subjective intoxication and sedation of alcohol at the low dose. Alcohol impaired performance on the RAVLT, and nicotine further impaired verbal learning and recall at both doses of alcohol. CONCLUSIONS: The data showed that nicotine had an effect on subjective alcohol effects but did not reverse and actually worsened alcohol-induced deficits in memory.
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Cognición/efectos de los fármacos , Etanol/farmacología , Nicotina/farmacología , Adulto , Método Doble Ciego , Etanol/administración & dosificación , Femenino , Humanos , Infusiones Intravenosas , Masculino , Nicotina/administración & dosificación , PlacebosRESUMEN
BACKGROUND: Nonlocalizing neurologic deficits detectable by clinical evaluation-"soft signs"-are a robust finding in patients diagnosed with schizophrenia, but their conceptual and neuroanatomical correlates remain unclear. The purpose of this study was to evaluate the organization of these deficits and their clinical correlates using the Neurological Evaluation Scale (NES). METHODS: Ninety-three male veterans with schizophrenia and schizoaffective disorder were evaluated using a detailed clinical assessment that included the NES, the Extrapyramidal Symptom Rating Scale, the Abnormal Involuntary Movement Scale (AIMS), the Barnes Akathisia Scale, the Positive and Negative Syndrome Scale, the Wisconsin Card Sorting Test (WCST), the Schedule for the Deficit Syndrome (SDS), and the Digit Symbol Substitution Task (DSST). RESULTS: Four factors explained 73% of the variance and had distinct clinical and neuropsychological correlates. Factor 1 reflected deficits involved with memory and sensory integration, and was associated with lower PANSS positive and higher AIMS scores. Factor 2 reflected impairments in motor control, and was associated with lower intelligence, more cognitive deficits, and deficit-syndrome schizophrenia. Factor 3 was related to lower intelligence and more perseverative errors on the WCST. Factor 4 was related to increasing age, more extrapyramidal symptoms, more perseverative errors, and worse scores on the DSST. CONCLUSIONS: Neurologic deficits in schizophrenia have an intrinsic organization that appears to have clinical significance, highlighting the continued utility of the NES in studies of neurological deficits in schizophrenia patients. The theoretical underpinning of this organization remains unclear.
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Examen Neurológico , Pruebas Neuropsicológicas , Trastornos Psicóticos/fisiopatología , Trastornos Psicóticos/psicología , Esquizofrenia/fisiopatología , Psicología del Esquizofrénico , Adulto , Factores de Edad , Cognición , Análisis Factorial , Femenino , Humanos , Inteligencia , Masculino , Memoria , Persona de Mediana Edad , Movimiento , Escalas de Valoración Psiquiátrica , Psicometría , SensaciónRESUMEN
BACKGROUND: The high rate of comorbidity of tobacco smoking with alcohol drinking suggests common neural substrates mediate the two addictive disorders. The beta(2)*-containing nicotinic acetylcholine receptor (beta(2)*-nAChR) has recently emerged as a prime candidate because some alpha and beta subunit genes have been linked to alcohol consumption and alcohol use behaviors. We hypothesized that beta(2)*-nAChR availability would be altered by alcohol in heavy drinking nonsmokers. METHODS: Eleven heavy drinking (mean age 39.6+/-12.1 years) and 11 age and sex-matched control (mean age 40.8+/-14.1 years) nonsmokers were imaged using [(123)I]5-IA-85380 ([(123)I]5-IA) single photon emission computed tomography (SPECT). Heavy alcohol drinkers drank varied amounts of alcohol (70-428/month) to facilitate exploratory linear analyses of the possible effects of alcohol. RESULTS: Heavy drinkers consumed on average 9.1+/-7.3 drinks/occasion; whereas controls drank 1.2+/-0.9 drinks/occasion. Heavy drinkers were imaged 2.0+/-1.6 days after last alcoholic beverage. Overall, there were no significant differences in beta(2)*-nAChR availability between the heavy drinking and control nonsmokers. Exploratory analyses of other factors that may be uniquely regulated by alcohol suggested no effects of age, number of alcohol drinks, years drinking, severity of drinking, craving or withdrawal. CONCLUSIONS: These preliminary analyses do not suggest a decrease in receptor availability in heavy drinking nonsmokers as compared to control nonsmokers. However, a larger study is warranted to explore effects of heavy alcohol drinking on other variables, such as sex, smoking, and genetic make up.
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Alcoholismo/diagnóstico por imagen , Receptores Nicotínicos/metabolismo , Adulto , Alcoholismo/psicología , Azetidinas , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Escalas de Valoración Psiquiátrica , Piridinas , Radiofármacos , Receptores Nicotínicos/genética , Fumar , Tomografía Computarizada de Emisión de Fotón ÚnicoRESUMEN
RATIONALE: A growing number of investigators are studying ketamine effects in healthy human subjects, but concerns remain about its safety as a research tool. Therefore, it is timely to revisit the safety of subanesthetic doses of ketamine in experimental psychopharmacology studies. OBJECTIVE: To report on the safety of laboratory studies with subanesthetic doses of ketamine in healthy humans using an existing dataset. MATERIALS AND METHODS: Medically healthy subjects with no personal or familial Axis I psychotic spectrum disorders were administered subanesthetic doses of ketamine by intravenous infusion in a series of clinical investigations from 1989 to 2005. The safety of ketamine administration was monitored in these subjects. RESULTS: Four hundred and fifty subjects received at least one dose of active ketamine. Eight hundred and thirty three active ketamine and 621 placebo infusions were administered. Ten adverse mental status events were documented in nine subjects/infusions that were deemed related to ketamine administration (2% of subjects, 1.45% of infusions). All but one adverse reaction resolved by the end of the test session. The side effects in the remaining individual were no longer clinically significant within 4 days of the test session. No residual sequelae were observed. CONCLUSION: Ketamine administration at subanesthetic doses appears to present an acceptable level of risk for carefully screened populations of healthy human subjects in the context of clinical research programs that intensively monitor subjects throughout their study participation.
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Antagonistas de Aminoácidos Excitadores/efectos adversos , Ketamina/efectos adversos , Trastornos Mentales/inducido químicamente , Adulto , Anciano , Ensayos Clínicos como Asunto , Relación Dosis-Respuesta a Droga , Antagonistas de Aminoácidos Excitadores/administración & dosificación , Femenino , Humanos , Infusiones Intravenosas , Ketamina/administración & dosificación , Masculino , Persona de Mediana Edad , Psicofarmacología , RiesgoRESUMEN
The purpose of this study was to determine whether schizophrenia was associated with alterations in alcohol response that might explain the elevated risk for AUDs in this population. In a randomized, double-blind, placebo-controlled, counter-balanced 3 test day laboratory study, the effects of alcohol were compared in 23 subjects with schizophrenia (without any previous alcohol use disorder (AUD) but with some alcohol exposure) and in 14 healthy subjects matched for age, gender, education, and lifetime exposure to alcohol. Standard alcohol drinks in a scheduled design were administered to produce blood alcohol levels of 0, 0.02-0.04 mg%, or 0.06-0.08 mg%. Schizophrenia symptoms, perceptual alterations, stimulant and depressant subjective effects of alcohol, and 'high' were measured before alcohol administration and at several post-drug time points. Verbal learning and recall, vigilance and distractibility, and motor function were assessed once per test day. Relative to healthy subjects, subjects with schizophrenia reported greater euphoria and stimulatory effects in response to alcohol. Alcohol produced small transient increases in positive psychotic symptoms and perceptual alterations without affecting negative symptoms. Alcohol also impaired several aspects of immediate and delayed recall, and vigilance, and distractibility. Schizophrenia patients showed increased euphoric and stimulatory responses to alcohol. These exaggerated positive responses to alcohol doses may contribute to the increased risk for AUDs associated with schizophrenia. The absence of 'beneficial' effects of alcohol does not support a self-medication hypothesis of alcohol use in schizophrenia.
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Trastornos del Sistema Nervioso Inducidos por Alcohol/fisiopatología , Encéfalo/efectos de los fármacos , Etanol/efectos adversos , Euforia/efectos de los fármacos , Esquizofrenia/fisiopatología , Psicología del Esquizofrénico , Adolescente , Adulto , Anciano , Trastornos del Sistema Nervioso Inducidos por Alcohol/complicaciones , Trastornos del Sistema Nervioso Inducidos por Alcohol/psicología , Nivel de Alerta/efectos de los fármacos , Nivel de Alerta/fisiología , Encéfalo/fisiopatología , Depresores del Sistema Nervioso Central/efectos adversos , Método Doble Ciego , Euforia/fisiología , Femenino , Humanos , Masculino , Trastornos de la Memoria/inducido químicamente , Trastornos de la Memoria/fisiopatología , Persona de Mediana Edad , Pruebas Neuropsicológicas , Efecto Placebo , Factores de Riesgo , Esquizofrenia/complicacionesRESUMEN
RATIONALE: Gender differences both in response to ketamine in animals and general cognitive functioning in humans have been observed and suggested to be related to modulatory effects of sex hormones on N-methyl-D: -aspartate receptor (NMDA-R) functioning. OBJECTIVES: The current study aimed to determine whether there were gender differences in response to ketamine in humans. METHODS: Behavioral data including positive and negative symptoms (Brief Psychiatric Rating Scale), perceptual alterations (Clinician-Administered Dissociative States Scale, CADSS), and "high" and "anxiety" states (Visual Analog Scale) from 295 subjects who participated in a total of 11 placebo-controlled ketamine studies were analyzed. In a subset of subjects, memory (Hopkins Verbal Learning Task: HVLT, n=108) and attention (continuous performance task, n=177) data were also analyzed. RESULTS: Male participants showed a greater performance decrement on the HVLT after ketamine administration compared to women. Men also reported a greater subjective sense of memory impairment on a CADSS subscale. No other gender differences in behavioral or cognitive measures were observed. CONCLUSIONS: Men showed a greater vulnerability to the amnestic effects of ketamine than women. Possible explanations of these findings are neuroanatomical and cognitive differences in processing of words in men and women and interactions between sex hormones and NMDA-R function.
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Amnesia/inducido químicamente , Antagonistas de Aminoácidos Excitadores/efectos adversos , Ketamina/efectos adversos , Memoria/efectos de los fármacos , Caracteres Sexuales , Adulto , Amnesia/psicología , Conducta/efectos de los fármacos , Escalas de Valoración Psiquiátrica Breve , Cognición/efectos de los fármacos , Método Doble Ciego , Antagonistas de Aminoácidos Excitadores/sangre , Femenino , Humanos , Ketamina/sangre , Masculino , Recuerdo Mental/efectos de los fármacos , Percepción/efectos de los fármacos , Valores de Referencia , Distribución por Sexo , Factores Sexuales , Aprendizaje Verbal/efectos de los fármacosRESUMEN
BACKGROUND: In healthy individuals, ketamine hydrochloride and amphetamine sulfate produce cognitive, behavioral, and subjective effects resembling endogenous psychoses. Studying the comparative and interactive effects of these agents may provide insights into the roles of the glutamate and monoamine systems in psychosis and cognition. OBJECTIVES: To directly compare the effects of ketamine and amphetamine and to explore their interactive effects within individuals. DESIGN: Placebo-controlled, randomized, double-blind psychopharmacologic trial. SETTING AND PARTICIPANTS: Forty-one healthy individuals recruited from the community who completed up to 4 test days. MAIN OUTCOME MEASURES: On each test day, participants received amphetamine (a 1-minute infusion of amphetamine sulfate, 0.25 mg/kg, or saline) and ketamine (a 1-minute intravenous infusion of ketamine, 0.23 mg/kg, followed by a 1-hour infusion of 0.5 mg/kg or an identical saline bolus and infusion). The order of amphetamine and ketamine infusions was randomized. RESULTS: At the doses studied, ketamine and amphetamine produced positive symptoms and euphoria. However, perceptual changes were produced only by ketamine, and hostility, grandiosity, and somatic concern were stimulated only by amphetamine. Amphetamine and ketamine produced conceptual disorganization, but only ketamine produced concrete ideation and unusual mannerisms. Ketamine produced negative symptoms and disrupted delayed recall. Ketamine and amphetamine showed 3 types of interactive effects: (1) amphetamine attenuated the impairment of working memory produced by ketamine; (2) amphetamine and ketamine had additive effects on thought disorder, arousal, and euphoria; and (3) amphetamine and ketamine had less-than-additive effects on psychosis. CONCLUSIONS: These findings implicate N-methyl-D-aspartate glutamate receptors and dopamine systems in psychosis. However, glutamate and dopamine may differentially contribute to psychosis, thought disorder, and euphoria. Regarding medication development for cognitive dysfunction, the pattern of the interactive effects of ketamine and amphetamine is consistent with the hypothesis that facilitation of prefrontal cortical dopamine levels would attenuate some cognitive impairments associated with deficits in N-methyl-D-aspartate receptor function.
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Anfetamina/farmacología , Cognición/efectos de los fármacos , Dopamina/fisiología , Glutamina/efectos de los fármacos , Glutamina/fisiología , Ketamina/farmacología , Psicosis Inducidas por Sustancias/etiología , Cognición/fisiología , Método Doble Ciego , Interacciones Farmacológicas , Humanos , Placebos , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/fisiopatología , Psicosis Inducidas por Sustancias/fisiopatología , Psicosis Inducidas por Sustancias/psicología , Receptores de N-Metil-D-Aspartato/efectos de los fármacos , Receptores de N-Metil-D-Aspartato/fisiologíaRESUMEN
RATIONALE: Sensitization to the effects of N-methyl-D-aspartate (NMDA) glutamate receptor antagonists is robust in animals. However, the applicability of this model to humans is unclear because it currently rests on highly confounded retrospective studies of individuals who experienced protracted psychoses following repeated binges with NMDA receptor antagonists. OBJECTIVES: The purpose of the current study was to determine whether there was evidence of sensitization to the behavioral effects of ketamine in healthy human subjects with repeated exposure to this drug. METHODS: Data were studied from 295 healthy human subjects who participated in one or more of 11 separate studies that involved ketamine administration over 14 years. Positive and negative symptoms (Brief Psychiatric Rating Scale: BPRS), perceptual alterations (Clinician-Administered Dissociative States Scale: CADSS), and "high" and "anxiety" states (Visual Analog Scale: VAS) that were measured in all studies were included as outcome measures. RESULTS: After including the number of previous exposures, number of previous studies, and time since first exposure as variables, repeated exposure to ketamine did not result in increased behavioral responses, suggestive of behavioral sensitization. CONCLUSIONS: The current data do not provide evidence that repeated exposure to ketamine, albeit limited, is associated with sensitization to the behavioral effects of ketamine.
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Conducta/efectos de los fármacos , Antagonistas de Aminoácidos Excitadores/farmacología , Ketamina/farmacología , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Adulto , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
BACKGROUND: Studies of pindolol augmentation of antidepressants in major depressive disorder have produced mixed results, and data in treatment-resistant patients are limited. Here, we report on a double-blind, randomized, controlled 6-week study of pindolol augmentation of selective serotonin reuptake inhibitors (SSRIs) in depressed outpatients resistant to SSRI monotherapy. METHOD: Forty-two outpatients with DSM-IV major depressive disorder who had an insufficient response to an adequate trial of an SSRI (fluoxetine, paroxetine, or sertraline) were randomly assigned to pindolol, 2.5 mg t.i.d., or sham augmentation, in addition to continued SSRI administration. For separate analysis, the control group underwent a single-blinded switch to pindolol, 2.5 mg t.i.d., from week 4 through week 6, while the active group was continued on pindolol augmentation (hemi-crossover design). Change in Hamilton Rating Scale for Depression (HAM-D) score from baseline to the end of week 3 was the primary outcome measure. Data were gathered from February 1994 to August 1998. RESULTS: Thirty-eight patients completed at least 1 week on protocol, with 21 and 17 randomly assigned to the pindolol and control groups, respectively. After 3 weeks on protocol, partial response rates (i.e., minimum 50% decrease from baseline in HAM-D score and maximum absolute score of 15) for the pindolol (19% [4/21]) and control (24% [4/17]) groups were comparable. At 3 weeks, the pindolol and control groups demonstrated mean +/- SD decreases in HAM-D scores of 6.5 +/- 9.8 and 9.7 +/- 7.2, respectively. There were no significant differences in antidepressant response or side effects between the 2 groups. CONCLUSION: These results do not support the efficacy of pindolol in augmenting clinical response to SSRIs in treatment-resistant depressed patients.