Behavioral response to diazepam in a residential laboratory

Changes in mood, cognitive performance and appetite in the late luteal and follicular phases of the menstrual cycle in women with and without PMDD (premenstrual dysphoric disorder)

Although it's been reported that women with premenstrual dysphoric disorder (PMDD) have increased negative mood, appetite (food cravings and food intake), alcohol intake and cognitive deficits premenstrually, few studies have examined these changes concurrently within the same group of women or compared to women without PMDD. Thus, to date, there is not a clear understanding of the full range of PMDD symptoms. The present study concurrently assessed mood and performance tasks in 29 normally cycling women (14 women who met DSM-IV criteria for PMDD and 15 women without PMDD). Women had a total of ten sessions: two practice sessions, 4 sessions during the follicular phase and 4 sessions during the late luteal phase of the menstrual cycle. Each session, participants completed mood and food-related questionnaires, a motor coordination task, performed various cognitive tasks and ate lunch. There was a significant increase in dysphoric mood during the luteal phase in women with PMDD compared to their follicular phase and compared to Control women. Further, during the luteal phase, women with PMDD showed impaired performance on the Immediate and Delayed Word Recall Task, the Immediate and Delayed Digit Recall Task and the Digit Symbol Substitution Test compared to Control women. Women with PMDD, but not Control women, also showed increased desire for food items high in fat during the luteal phase compared to the follicular phase and correspondingly, women with PMDD consumed more calories during the luteal phase (mostly derived from fat) compared to the follicular phase. In summary, women with PMDD experience dysphoric mood, a greater desire and actual intake of certain foods and show impaired cognitive performance during the luteal phase. An altered serotonergic system in women with PMDD may be the underlying mechanism for the observed symptoms; correspondingly, treatment with specific serotonin reuptake inhibitors (SSRIs) remains the preferred treatment at this time.

Enhanced sucrose pellet consumption induced by benzodiazepine-type drugs in squirrel monkeys: role of GABAA receptor subtypes

RATIONALE

Benzodiazepine agonists characteristically increase food intake in humans and non-human subjects, and the underlying mechanisms of this effect are not understood completely.

OBJECTIVE

Compounds with selectivity for GABAA receptor subtypes were used to evaluate the role of GABAA receptors containing alpha1 and alpha5 subunits (alpha1GABAA and alpha5GABAA receptors, respectively) in benzodiazepine-induced increases in sucrose pellet consumption.

MATERIALS AND METHODS

Adult male squirrel monkeys (N=4-6), maintained under free-feeding conditions, were administered with intramuscular injections of the nonselective benzodiazepines diazepam and alprazolam, the alpha1GABAA-preferring compounds zolpidem and zaleplon, or the alpha5GABAA-preferring agonist QH-ii-066 before daily 10-min periods when sucrose pellets were available. In a separate experiment, observable behavioral effects (e.g., ataxia and procumbent posture) were quantified after administration of alprazolam, zaleplon, and QH-ii-066. To further assess the roles of GABAA receptor subtypes, zolpidem-induced increases in pellet consumption were re-evaluated after pretreatment with nonselective antagonist flumazenil, the alpha1GABAA-preferring antagonist beta-carboline-3-carboxylate-t-butyl ester (BCCT), or QH-ii-066.

RESULTS

Alprazolam, diazepam, zolpidem, and zaleplon but not QH-ii-066 significantly increased sucrose pellet consumption. In addition, all agonists decreased locomotion and environment-directed behavior as well as engendered ataxia and procumbent posture. For all compounds except QH-ii-066, these behaviors occurred at doses similar to those that increased pellet consumption. Flumazenil and BCCT, but not QH-ii-066, antagonized zolpidem-induced increases in pellet consumption in a surmountable fashion.

CONCLUSION

These results suggest that the alpha1GABAA receptor subtype plays a key role in benzodiazepine-induced increases in consumption of palatable food, whereas the alpha5GABAA receptor subtype may not be involved in this effect.

Zolpidem-related effects on performance and mood during simulated night-shift work

The effects of zolpidem, a nonbenzodiazepine hypnotic, on psychomotor task performance, subjective effects, and food intake were examined during simulated shift work. Seven participants completed this 23-day, within-participant design, residential laboratory study. They received a single oral zolpidem dose (0, 5, or 10 mg) 1 hr before bedtime for 3 consecutive days under 2 shift conditions: day shift and night shift. When participants received placebo, next-day performance and subjective effects were disrupted, and food intake was decreased during the night shift. Zolpidem improved subjective reports of sleep quality and, to a lesser extent, next-day performance. Next-day mood, however, was worsened by zolpidem. Food intake was unaffected by zolpidem. These data indicate that shift changes produce performance impairments, mood alterations, and decreases in food intake, and that zolpidem attenuates some shift-change-related disruptions.

What is the role of dopamine in reward: hedonic impact, reward learning, or incentive salience?

What roles do mesolimbic and neostriatal dopamine systems play in reward? Do they mediate the hedonic impact of rewarding stimuli? Do they mediate hedonic reward learning and associative prediction? Our review of the literature, together with results of a new study of residual reward capacity after dopamine depletion, indicates the answer to both questions is 'no'. Rather, dopamine systems may mediate the incentive salience of rewards, modulating their motivational value in a manner separable from hedonia and reward learning. In a study of the consequences of dopamine loss, rats were depleted of dopamine in the nucleus accumbens and neostriatum by up to 99% using 6-hydroxydopamine. In a series of experiments, we applied the 'taste reactivity' measure of affective reactions (gapes, etc.) to assess the capacity of dopamine-depleted rats for: 1) normal affect (hedonic and aversive reactions), 2) modulation of hedonic affect by associative learning (taste aversion conditioning), and 3) hedonic enhancement of affect by non-dopaminergic pharmacological manipulation of palatability (benzodiazepine administration). We found normal hedonic reaction patterns to sucrose vs. quinine, normal learning of new hedonic stimulus values (a change in palatability based on predictive relations), and normal pharmacological hedonic enhancement of palatability. We discuss these results in the context of hypotheses and data concerning the role of dopamine in reward. We review neurochemical, electrophysiological, and other behavioral evidence. We conclude that dopamine systems are not needed either to mediate the hedonic pleasure of reinforcers or to mediate predictive associations involved in hedonic reward learning. We conclude instead that dopamine may be more important to incentive salience attributions to the neural representations of reward-related stimuli. Incentive salience, we suggest, is a distinct component of motivation and reward. In other words, dopamine systems are necessary for 'wanting' incentives, but not for 'liking' them or for learning new 'likes' and 'dislikes'.

Possible involvement of nitric oxide in chlordiazepoxide-induced feeding in the mouse

Two experiments investigated a possible role of nitric oxide (NO) in chlordiazepoxide (CP)-induced feeding in nondeprived male ICR mice in independent groups designs. Experiment 1 demonstrated a dose-related decrease in CP-induced solid food intake over a 60-min test period with increasing dose (10, 25, and 50 mg/ kg SC) of the NO-synthase (NOS) inhibitor, L-NG-nitro arginine (L-NOARG), reaching statistical significance at 10 mg/kg L-NOARG when compared to vehicle control. Identical doses of L-NOARG failed to significantly affect normal feeding in vehicle treated mice. In Experiment 2, initial pretreatment with L-arginine (500 and 1000 mg/kg IP) partially or completely restored the feeding inhibitory action of a challenge dose (25 mg/kg SC) of L-NOARG; D-arginine (500 mg/kg IP) was ineffective, thus supporting a stereospecific action of arginine. Arginine isomers did not differentially affect intake in normal feeding animals. These results implicate involvement of NO in CP-induced hyperphagia; they are consistent with and extend research linking NO and ingestive behaviors.

Nitrous oxide induces feeding in the nondeprived rat that is antagonized by naltrexone

Three experiments investigated a possible effect of nitrous oxide (N2O) on food intake in nondeprived male hooded rats in independent groups designs. Experiment 1 demonstrated a concentration-related increase in intake with increasing level of nitrous oxide (10-40% N2O), reaching statistical significance at 20% N2O when compared to room air controls (p < 0.05). In experiment 2, pretreatment with 10 and 20 mg/kg of the benzodiazepine antagonist, flumazenil, failed to significantly attenuate 30% N2O-induced hyperphagia. In Experiment 3, pretreatment with the opioid antagonist, naltrexone, effectively antagonized 30% N2O-induced hyperphagia. Pronounced attenuation (to 59% of 30% N2O-induced intake level over a 1 h period) at the lowest dose of naltrexone (0.1 mg/kg, p < 0.01) compared to vehicle level resulted in a shallow dose-response curve across the dose range tested (0.1-10.0 mg/kg). These results suggest that an endogenous opioid mechanism is prominently involved in the N2O-induced ingestive response.

Effects of delta 9-tetrahydrocannabinol and social context on marijuana self-administration by humans

The effects of time of day and social context on daily patterns of marijuana self-administration were examined in two groups of three adult male marijuana smokers during a 12-day residential study. Days were divided into 6.5-h work and social-access periods. Order of occurrence (i.e., work before social access or social access before work) was counterbalanced between groups and reversed for both groups on day 8. Up to eight marijuana cigarettes (0.0% or 2.3% delta 9-THC) could be smoked each day. Stable patterns of marijuana smoking were observed across days for each subject. Three subjects smoked more marijuana during the social-access period, regardless of when it occurred. The other three smoked more marijuana during the first period, regardless of whether it was a work or social-access period. The number of marijuana cigarettes smoked was unrelated to THC content. In contrast, subjective reports of "High," "Liking," "Potency" and "Drug" on visual-analog scales were increased on active marijuana days. Subjective reports of drug effects were not predictive of drug self-administration.