Scott E. Lukas

Buprenorphine treatment of refractory depression

Opiates were used to treat major depression until the mid-1950s. The advent of opioids with mixed agonist-antagonist or partial agonist activity, with reduced dependence and abuse liabilities, has made possible the reevaluation of opioids for this indication. This is of potential importance for the population of depressed patients who are unresponsive to or intolerant of conventional antidepressant agents. Ten subjects with treatment-refractory, unipolar, nonpsychotic, major depression were treated with the opioid partial agonist buprenorphine in an open-label study. Three subjects were unable to tolerate more than two doses because of side effects including malaise, nausea, and dysphoria. The remaining seven completed 4 to 6 weeks of treatment and as a group showed clinically striking improvement in both subjective and objective measures of depression. Much of this improvement was observed by the end of 1 week of treatment and persisted throughout the trial. Four subjects achieved complete remission of symptoms by the end of the trial (Hamilton Rating Scale for Depression scores < or = 6), two were moderately improved, and one deteriorated. These findings suggest a possible role for buprenorphine in treating refractory depression.

Sex differences in plasma cocaine levels and subjective effects after acute cocaine administration in human volunteers

Gender differences after acute cocaine administration have received little attention in spite of the fact that males and females respond differently to many drugs. Seven male and seven female occasional cocaine users received both an intranasal dose of cocaine hydrochloride (0.9 mg/kg) and placebo powder in a randomized order and reported subjective effects via an instrumental joystick device and various questionnaires. Blood samples were withdrawn at 5-min intervals to assess pharmacokinetic differences. Male subjects achieved the highest peak plasma cocaine levels (144.4 ± 17.5 ng/ml), detected cocaine effects significantly faster than females and also experienced a greater number of episodes of intense good and bad effects. Women studied during the follicular phase of their menstrual cycle had peak plasma cocaine levels of 73.2 ± 9.9 ng/ml, which was significantly higher than when they were studied during their luteal phase (54.7 ± 8.7 ng/ml), but there were no differences in their subjective reports of cocaine effects. In spite of the different cocaine blood levels and subjective effects, peak heart rate increases did not differ between males and females suggesting that women may be more sensitive than males to the cardiovascular effects of cocaine. These data suggest that there are significant gender and menstrual cycle differences in the response to acute intranasal cocaine administration and these differences may have implications for the differential abuse of this drug.

Increased aggressive responding in male volunteers following the administration of gradually increasing doses of testosterone cypionate

The present study assessed the effects of supraphysiologic doses of testosterone on aggressive responding in a controlled laboratory setting. Eight male subjects received gradually increasing doses of testosterone cypionate (150 mg/week for two weeks, 300 mg/week for two weeks, and 600 mg/week for two weeks) or placebo using a double-blind, randomized, cross-over design. Subjects were tested both before and after the series of injections. During the experimental session subjects could press a button to accumulate points exchangeable for money (non-aggressive response) or press another button to subtract points from a fictitious opponent (aggressive response). Aggressive responding was instigated by subtracting points from the subject which was attributable to the fictitious opponent. Testosterone administration resulted in a significantly higher number of aggressive responding compared to placebo.

EEG alpha activity increases during transient episodes of ethanol-induced euphoria

The effects of acute ethanol administration were studied in 18 men to determine the electroencephalographic (EEG) correlates of ethanol-induced behavioral changes. Subjects were instructed to operate an instrumental device to indicate changes in their subjective mood state while EEG activity and plasma ethanol levels were continuously measured. Three groups of 6 subjects consumed either placebo, 0.347 g/kg ethanol or 0.695 g/kg ethanol over a 15 min period. EEG and behavioral changes were directly correlated with plasma ethanol levels during the ascending limb of the plasma ethanol curve. Theta EEG activity increased proportionally as plasma ethanol levels increased during the 2 hr recording session. Alpha EEG activity increased during the first hour and then returned to control levels. The increased alpha activity was most prominent when subjects reported feeling intense pleasure or euphoria. Power spectral analysis of discrete samples of EEG activity revealed that transient increases in alpha activity paralleled the onset of ethanol-induced euphoria. These data suggest that ethanol-induced behavioral effects are associated with discrete changes in brain electrical activity.

Age of onset of marijuana use and executive function.

Marijuana (MJ) remains the most widely abused illicit substance in the United States, and in recent years, a decline in perceived risk of MJ use has been accompanied by a simultaneous increase in rates of use among adolescents. In this study, the authors hypothesized that chronic MJ smokers would perform cognitive tasks, specifically those that require executive function, more poorly than control subjects and that individuals who started smoking MJ regularly prior to age 16 (early onset) would have more difficulty than those who started after age 16 (late onset). Thirty-four chronic, heavy MJ smokers separated into early and late onset groups, and 28 non-MJ smoking controls completed a battery of neurocognitive measures. As hypothesized, MJ smokers performed more poorly than controls on several measures of executive function. Age of onset analyses revealed that these between-group differences were largely attributed to the early onset group, who were also shown to smoke twice as often and nearly 3 times as much MJ per week relative to the late onset smokers. Age of onset, frequency, and magnitude of MJ use were all shown to impact cognitive performance. Findings suggest that earlier MJ onset is related to poorer cognitive function and increased frequency and magnitude of MJ use relative to later MJ onset. Exposure to MJ during a period of neurodevelopmental vulnerability, such as adolescence, may result in altered brain development and enduring neuropsychological changes.

Changes in aggressive behavior during withdrawal from long-term marijuana use

Rationale: Even though marijuana is the most commonly abused illicit drug in the United States, it is still undetermined whether withdrawal after chronic use results in changes in aggressive behavior in humans. Objective: The present study investigated the pattern and duration of changes in aggressive behavior in long-term marijuana users during a 28-day abstinence period verified by daily urines. Methods: Chronic marijuana users who had smoked marijuana on at least 5000 occasions (the equivalent of smoking daily for approximately 14 years) and who were smoking regularly when recruited were studied on days 0 (when they were still smoking), 1 (during acute withdrawal), 3, 7 and 28 of a 28-day detoxification period. Aggressive behavior was measured using the Point Subtraction Aggression Paradigm. Results: Compared to controls and to the pre-withdrawal data, chronic marijuana users displayed more aggressive behavior on days 3 and 7 of marijuana abstinence. These increases in aggressive responding returned to pre-withdrawal levels after 28 days and were paralleled by small, non-significant changes in depression and anxiety scores. Conclusions: Our findings confirm previous reports of an abstinence syndrome associated with chronic marijuana use and suggest that aggressive behavior should be an additional component of this syndrome.

Self-injection of barbiturates and benzodiazepines in baboons

Self-injection of three barbiturates, six benzodiazepines, and chlorpromazine was examined in baboons. Intravenous injections of drug were dependent upon completion of 160 lever presses (a 160-response fixed-ratio schedule). A 3-h time-out period followed each injection, permitting a maximum of eight injections per day. Prior to testing each dose of drug, self-injection performance was established with cocaine. Subsequently, a test dose was substituted for cocaine. Amobarbital, pentobarbital, and secobarbital maintained the highest levels of self-injection, which were similar to those maintained by cocaine. Clonazepam, clorazepate, diazepam, flurazepam, medazepam, and midazolam maintained relatively modest levels of self-injection, while chlorpromazine maintained only low levels, which were in the range of vehicle control. Of the six benzodiazepines, midazolam produced the highest levels of self-injection. At the highest self-injected doses, the barbiturates produced anesthesia in contrast to the benzodiazepines, which produced only sedation. None of the drugs affected food intake except for chlorpromazine, which produced dose-related decreases. The differences among the drug classes (i.e., barbiturate, benzodiazepine, phenothiazine) with respect to the maintenance of self-injection correspond well with the results of previous animal and human drug self-administration studies.

Food Intake and Reward Mechanisms in Patients with Schizophrenia: Implications for Metabolic Disturbances and Treatment with Second-Generation Antipsychotic Agents

Obesity is highly prevalent among patients with schizophrenia and is associated with detrimental health consequences. Although excessive consumption of fast food and pharmacotherapy with such second-generation antipsychotic agents (SGAs) as clozapine and olanzapine has been implicated in the schizophrenia/obesity comorbidity, the pathophysiology of this link remains unclear. Here, we propose a mechanism based on brain reward function, a relevant etiologic factor in both schizophrenia and overeating. A comprehensive literature search on neurobiology of schizophrenia and of eating behavior was performed. The collected articles were critically reviewed and relevant data were extracted and summarized within four key areas: (1) energy homeostasis, (2) food reward and hedonics, (3) reward function in schizophrenia, and (4) metabolic effects of the SGAs. A mesolimbic hyperdopaminergic state may render motivational/incentive reward system insensitive to low salience/palatability food. This, together with poor cognitive control from hypofunctional prefrontal cortex and enhanced hedonic impact of food, owing to exaggerated opioidergic drive (clinically manifested as pain insensitivity), may underlie unhealthy eating habits in patients with schizophrenia. Treatment with SGAs purportedly improves dopamine-mediated reward aspects, but at the cost of increased appetite and worsened or at least not improved opiodergic capacity. These effects can further deteriorate eating patterns. Pathophysiological and therapeutic implications of these insights need further validation via prospective clinical trials and neuroimaging studies.

Precipitated diazepam withdrawal in baboons: Effects of dose and duration of diazepam exposure

Baboons were exposed to diazepam via continuous injection at doses of 0.125-20.0 mg/kg per day intragastrically (i.g.) for 7 days or to 20 mg/kg per day, i.g. for 1 h or 1 to 35 days. After diazepam administration, Ro 15-1788, a benzodiazepine antagonist was given (5.0 mg/kg i.m.) and precipitated benzodiazepine withdrawal was evaluated by scoring individual signs. The severity of the withdrawal, as indicated by the number of the different signs as well as by frequency of individual signs, increased as the dose and duration of diazepam exposure were increased. Consistent elevations in diazepam withdrawal signs were evident after a dose as low as 0.25 mg/kg per day for 7 days and after administration of 20 mg/kg per day for as short as 3-7 days. Data also suggested that history of previous benzodiazepine exposure sensitized animals to subsequent development of physical dependence. Overall, this study suggests that benzodiazepines produce meaningful functional changes in the central nervous system after exposure to relatively low doses and after relatively short durations of exposure.

Electroencephalographic activity and plasma ACTH during ethanol-induced euphoria ☆

Covariance of brain electrical activity (EEG), plasma adrenocorticotrophic hormone (ACTH) and cortisol levels, and mood states were determined for healthy adult men during the first 2 hr after ingestion of ethanol or ethanol placebo under controlled double-blind conditions. Analysis of integrated plasma ACTH and cortisol levels at 5-min intervals, EEG power spectral analysis during consecutive 2-min epochs, and continuous assessment of mood states with a nonverbal instrumental device were carried out during the ascending phase of the blood ethanol curve. Ethanol induced rapid changes in brain electrical activity and plasma ACTH levels that were significantly correlated with subjective perception of changes in mood. The paroxysmal short epochs of euphoria associated with electroencephalographic and ACTH responses during the ascending phase of the blood ethanol curve may reflect physiological concomitants of pharmacological and behavioral reinforcers that enhance risk for perpetuation of drinking and alcohol abuse.