The Contribution of Autonomic Imbalance to the Development of Metabolic Syndrome.

OBJECTIVES: Obesity, diabetes, and heart disease-the most costly epidemics of our time-share a common but rarely treated mechanism: autonomic imbalance. We examined the contribution of autonomic imbalance, relative to selected demographic and biobehavioral risk factors, to the development of metabolic syndrome in a community sample for 12 years. METHODS: We identified offspring cohort participants from the Framingham Heart Study who did not have metabolic syndrome at Examination 3 (1983-1987, baseline for this analysis) and whose metabolic syndrome status was assessed at the 4-, 8-, and 12-year follow-ups. We created logistic regression models, using baseline resting heart rate (RHR) and heart rate variability (HRV), to predict the odds of developing metabolic syndrome within 12 years, adjusting for age, sex, depressive symptoms, and smoking. HRV indices (standard deviation of the beat-to-beat interval [SDNN] and root mean square of the standard deviation) were calculated from 2-hour Holter monitor data. RESULTS: Our sample consisted of 1143 participants (mean [SD] age = 46.6 (9.9) years, 57% female). One standard deviation of a decrease in SDNN increased the odds of developing metabolic syndrome within 12 years by 43% (95% confidence interval = 1.302-1.572, p < .001). Without HRV in the model, each increase in RHR of 10 beats/min increased the odds of developing metabolic syndrome by 24% (95% confidence interval = 1.094-1.426, p < .001). CONCLUSIONS: In this community sample, low HRV by both measures (SDNN and root mean square of the standard deviation), high RHR, increased age, cigarette smoking, and being male significantly increased the odds of developing metabolic syndrome within 12 years of baseline.

Localization of P-gp (Abcb1) and Mrp2 (Abcc2) in freshly isolated rat hepatocytes.

Freshly isolated hepatocytes are widely accepted as the "gold standard" for providing reliable data on drug uptake across the sinusoidal (basolateral) membrane. However, the suitability of freshly isolated hepatocytes in suspension to assess efflux by canalicular (apical) proteins or predict biliary excretion in the intact organ is unclear. After collagenase digestion, hepatocytes rapidly lose polarity, but localization of canalicular transport proteins in the first few hours after isolation has not been well characterized. In this study, immunostaining and confocal microscopy have provided, for the first time, a detailed examination of canalicular transport protein localization in freshly isolated rat hepatocytes fixed within 1 h of isolation and in cells cultured for 1 h. Organic anion transporting polypeptide 1a1 (Oatp1a1) was expressed in all hepatocytes and distributed evenly across the basolateral membrane; there was no evidence for colocalization of Oatp1a1 with P-glycoprotein (P-gp) or multidrug resistance-associated protein 2 (Mrp2). In contrast, P-gp and Mrp2 expression was lower than Oatp1a1 and confined to junctions between adjacent cells, intracellular compartments, and "legacy" network structures at or near the cell surface. P-gp and Mrp2 staining was more predominant in regions adjacent to former canalicular spaces, identified by zonula occludens-1 staining. Functional analysis of rat hepatocytes cultured for 1 h demonstrated that the fluorescent anion and Mrp2 substrate, 5-(and-6)-carboxy-2',7'-dichlorofluorescein (CDF), accumulated in cellular compartments; compartmental accumulation of CDF was sensitive to (E)-3-[[[3-[2-(7-chloro-2-quinolinyl)ethenyl]phenyl]-[[3-dimethylamino)-3-oxopropyl]thio]methyl]thio]-propanoic acid (MK571, Mrp inhibitor) and was not observed in hepatocytes isolated from Mrp2-deficient rats. Drug efflux from freshly isolated hepatocytes as an estimate of apical efflux/biliary excretion would give an inaccurate assessment of true apical elimination and, as such, should not be used to make in vivo extrapolations.

The role of impulsive behavior in drug abuse.

BACKGROUND: Impulsivity is a multifaceted construct that has recently been recognized as a factor contributing to enhanced vulnerability to drug abuse. OBJECTIVES: In the present review, we focus on two facets of impulsivity (and tasks that measure them): (1) impulsive choice (delay discounting task) and (2) inhibitory failure (go/no-go, stop signal reaction time, and five-choice serial reaction time tasks). We also describe how performance on each of these tasks is associated with drug-related behavior during phases of drug abuse that capture the essential features of addiction (acquisition, escalation, and reinstatement of drug-seeking after drug access has terminated). Three hypotheses (H) regarding the relationship between impulsivity and drug abuse are discussed: (1) increased levels of impulsivity lead to drug abuse (H1), (2) drugs of abuse increase impulsivity (H2), and (3) impulsivity and drug abuse are associated through a common third factor (H3). CONCLUSION: Impulsivity expressed as impulsive choice or inhibitory failure plays a role in several key transition phases of drug abuse. There is evidence to support all three nonexclusive hypotheses. Increased levels of impulsivity lead to acquisition of drug abuse (H1) and subsequent escalation or dysregulation of drug intake. Drugs of abuse may increase impulsivity (H2), which is an additional contributor to escalation/dysregulation. Abstinence, relapse, and treatment may be influenced by both H1 and H2. In addition, there is a relationship between impulsivity and other drug abuse vulnerability factors, such as sex, hormonal status, reactivity to nondrug rewards, and early environmental experiences that may impact drug intake during all phases of addiction (H3). Relating drug abuse and impulsivity in phases of addiction via these three hypotheses provides a heuristic model from which future experimental questions can be addressed.

Impulsive choice and environmental enrichment: effects of d-amphetamine and methylphenidate.

Individual differences in impulsive choice and rearing in differential environments are factors that predict vulnerability to drug abuse. The present study determined if rearing influences impulsive choice, and if d-amphetamine or methylphenidate alters impulsive choice in differentially reared rats. Male Sprague-Dawley rats were raised from 21 days of age in either an enriched condition (EC) or an isolated condition (IC) and were tested as young adults on an adjusting delay task. In this task, two levers were available and a response on one lever yielded one 45mg food pellet immediately, whereas a response on the other yielded three pellets after an adjusting delay. The delay was initially set at 6s, and it decreased or increased by 1s following responses on the immediate or delayed levers, respectively. A mean adjusted delay (MAD) was calculated upon completion of each daily session, and it served as the quantitative measure of impulsivity. Once MADs stabilized, rats were injected with saline, d-amphetamine (0.5, 1.0, or 2.0mg/kg, s.c.), or methylphenidate (2.5, 5.0, or 10.0mg/kg, s.c.) 15min prior to adjusting delay sessions. EC rats had higher baseline MADs (were less impulsive) than IC rats. Additionally, administration of d-amphetamine, but not methylphenidate, dose-dependently increased impulsive choice (decreased MADs) in EC rats. In IC rats, d-amphetamine and methylphenidate dose-dependently decreased impulsivity (increased MADs). These results indicate that rearing environment influences impulsive choice and moderates the effect of psychostimulants on impulsive choice. Specifically, psychostimulants may decrease environment-dependent impulsive choice in individuals with high levels of impulsivity (e.g., those with ADHD), whereas they may increase impulsive choice in individuals with low levels of impulsivity.

Effects of altering reinforcer magnitude and reinforcement schedule on phencyclidine (PCP) self-administration in monkeys using an adjusting delay task.

Compared to nondrug reinforcers, few studies have examined delay discounting for drug reinforcers. The purpose of the present study was to examine delay discounting in rhesus monkeys using orally delivered phencyclidine (PCP) as the reinforcer and to examine the effects of manipulating reinforcer magnitude and cost on delay discounting for PCP using an adjusting delay task. Monkeys could choose between a single delivery of PCP available immediately or a bundle of PCP deliveries available following a titrated delay. The average of the delays, or the mean adjusted delay (MAD), served as the quantitative measure of delay discounting. In Experiment 1, reinforcer magnitude was manipulated by varying the PCP concentration and the size of the delayed reinforcer (6 or 12 deliveries). The concentration-effect curve for PCP deliveries assumed an inverted U-shaped function, but varying PCP concentration had little effect on MAD values or the choice between immediate and delayed reinforcers. Increasing the size of the delayed reinforcer produced an upward and leftward shift in the concentration-effect curve. In Experiment 2, the cost of reinforcers was manipulated by increasing the fixed ratio (FR) requirement for each choice. Increasing the FR led to increased MAD values and decreased PCP self-administration.

Impulsive choice as a predictor of acquisition of IV cocaine self- administration and reinstatement of cocaine-seeking behavior in male and female rats.

Drug abuse and impulsive choice are related in humans. In female rats, impulsive choice predicted the rate of acquisition of IV cocaine self-administration. The objectives of the present experiments were to: (a) compare impulsive choice in males and females, (b) extend previous research on impulsive choice and acquisition of cocaine self-administration to males, and (c) compare males and females during maintenance, extinction, and reinstatement of cocaine-seeking behavior. Male and female rats were trained on an adjusting delay task in which a response on one of two levers yielded one food pellet immediately, and a response on the other resulted in three pellets after an adjusting delay that decreased after responses on the immediate lever and increased after responses on the delay lever. A mean adjusted delay (MAD) was used as the quantitative measure of impulsivity. In Experiment 1, MADs were analyzed for sex differences. In Experiment 2, acquisition of cocaine self-administration was examined in rats selected for high (HiI; MADs < or =9 seconds) or low (LoI; MADs > or =13 seconds) impulsivity. In Experiment 3, HiI and LoI groups were compared on maintenance and extinction of cocaine self-administration and cocaine-primed reinstatement of drug-seeking behavior. There were no sex differences in impulsive choice; however, HiI male and female rats acquired cocaine self-administration faster than their LoI counterparts. LoI females responded more on a cocaine-associated lever during maintenance and extinction than HiI females, but HiI females showed greater reinstatement of cocaine-seeking behavior than all other groups at the highest dose tested (15 mg/kg). Thus, individual differences in impulsive choice were associated with differences in cocaine-seeking behavior. Impulsive choice and sex may be additive vulnerability factors in certain phases of drug abuse.

Acquisition of i.v. cocaine self-administration in adolescent and adult male rats selectively bred for high and low saccharin intake.

Adolescence and excessive intake of saccharin have each been previously associated with enhanced vulnerability to drug abuse. In the present study, we focused on the relationship between these two factors using male adolescent and adult rats selectively bred for high (HiS) and low (LoS) levels of saccharin intake. On postnatal day 25 (adolescents) or 150 (adults), rats were implanted with an intravenous catheter and trained to self-administer cocaine (0.4 mg/kg) using an autoshaping procedure that consisted of two 6-h sessions. In the first 6 h, rats were given non-contingent cocaine infusions at random intervals 10 times per hour, and during the second 6-h session, rats were allowed to self-administer cocaine under a fixed ratio 1 (FR 1) lever-response contingency. Acquisition was defined as a total of at least 250 infusions over 5 consecutive days, and rats were given 30 days to meet the acquisition criterion. Subsequently, saccharin phenotype scores were determined by comparing 24-h saccharin and water consumption in two-bottle tests to verify HiS/LoS status. Adolescent LoS rats had a faster rate of acquisition of cocaine self-administration than adult LoS rats; however, adolescent and adult HiS rats acquired at the same rate. Both HiS and LoS adolescents had significantly higher saccharin phenotype scores than HiS and LoS adults, respectively. Additionally, saccharin score was negatively correlated with the number of days to meet the acquisition criterion for cocaine self-administration, but this was mostly accounted for by the HiS adolescents. These results suggest that during adolescence, compared with adulthood, rats have both an increased avidity for sweets and vulnerability to initiate drug abuse.

Social stimuli enhance phencyclidine (PCP) self-administration in rhesus monkeys.

Environmental factors, including social interaction, can alter the effects of drugs of abuse on behavior. The present study was conducted to examine the effects of social stimuli on oral phencyclidine (PCP) self-administration by rhesus monkeys. Ten adult rhesus monkeys (M. mulatta) were housed side by side in modular cages that could be configured to provide visual, auditory, and olfactory stimuli provided by another monkey located in the other side of a paired unit. During the first experiment, monkeys self-administered PCP (0.25 mg/ml) and water under concurrent fixed ratio (FR) 16 schedules of reinforcement with either a solid or a grid (social) partition separating each pair of monkeys. In the second experiment, a PCP concentration-response relationship was determined under concurrent progressive ratio (PR) schedules of reinforcement during both the solid and grid partition conditions. Under the concurrent FR 16 schedules, PCP and water self-administration were significantly higher during exposure to a cage mate through a grid partition than when a solid partition separated the monkeys. The relative reinforcing strength of PCP, as measured by PR break points, was greater during the grid partition condition compared to the solid partition condition indicated by an upward shift in the concentration-response curve. To determine whether the social stimuli provided by another monkey led to activation of the hypothalamic-pituitary-adrenal (HPA) axis, which may have evoked the increase of PCP self-administration during the grid partition condition, a third experiment was conducted to examine cortisol levels under the two housing conditions. A modest, but nonsignificant increase in cortisol levels was found upon switching from the solid to the grid partition condition. The results suggest that social stimulation among monkeys in adjoining cages leads to enhanced reinforcing strength of PCP.

Impulsivity (delay discounting) for food and cocaine in male and female rats selectively bred for high and low saccharin intake.

Previous research in rats indicates that delay discounting for food, a model of impulsivity, predicted the rate of acquisition of cocaine self-administration. In other studies, rats bred for high saccharin intake (HiS) acquired cocaine self-administration at higher rates than those with low saccharin intake (LoS), and female (F) rats acquired cocaine self-administration more rapidly than males (M). The purpose of this study was to examine a possible connection between impulsivity, saccharin intake, and sex by comparing M and F rats from the HiS and LoS selectively bred lines on measures of impulsivity; i.e., their rate of delay discounting for food or i.v. cocaine infusions. The adjusting delay procedure allowed rats access to 2 response levers, and a pellet dispenser or an i.v. drug infusion pump. In 4 groups (HiS M, HiS F, LoS M, LoS F) responses under a fixed-ratio (FR) 1 schedule on one lever resulted in one 45 mg pellet immediately, and responses on the other lever resulted in 3 or 6 pellets after a delay. Four additional groups received either a small cocaine (0.2, 0.4, or 0.8 mg/kg) infusion immediately or a delayed larger infusion (3x the amount of the small infusions). The delay to the larger reinforcer began at 6 s and increased or decreased by 1 s following responses on the delay or immediate levers, respectively. A mean adjusted delay (MAD) was calculated over 30 choice trials during each daily 3-hour session, and it was used as a quantitative measure of impulsivity. In groups maintained by food, HiS rats were more impulsive (lower MADs) than LoS rats, and LoS females were more impulsive than LoS males. There were no phenotype or sex differences in delay discounting for cocaine. Understanding the relationship between impulsivity and other predictors of drug abuse (e.g., sex, saccharin intake) is important in developing prevention and treatment strategies.

Escalation of i.v. cocaine self-administration and reinstatement of cocaine-seeking behavior in rats bred for high and low saccharin intake.

RATIONALE: Rats selectively bred for high saccharin (HiS) intake consume more alcohol, acquire intravenous (i.v.) cocaine self-administration more rapidly, and show more dysregulated patterns of cocaine self-administration than their low saccharin-consuming (LoS) counterparts. OBJECTIVES: The purpose of the present study was to determine whether HiS and LoS rats also differ in the escalation, maintenance, extinction, and reinstatement of i.v. cocaine self-administration. MATERIALS AND METHODS: Two experiments were conducted in separate groups of rats. In the first experiment, HiS and LoS female rats were allowed to self-administer cocaine [0.4 mg/kg; fixed ratio (FR) 1] under short (ShA, 2 h per day) or long (LgA, 12 h per day) access conditions for 21 days. Session lengths were subsequently equated (2 h), and FR1-maintained cocaine self-administration was examined. In the second experiment, additional groups of HiS and LoS female rats were given access to cocaine (0.4 mg/kg; FR 1) self-administration during 2-h sessions for 10 days. Subsequently, saline was substituted for cocaine, and responding was extinguished. After a 14-day extinction period, saline- and cocaine-[5, 10, and 15 mg/kg, intraperitoneal (i.p.)] induced reinstatement of drug-seeking behavior was measured. RESULTS: HiS LgA rats escalated their cocaine intake more rapidly than LoS rats, and during the 2 h sessions after escalation cocaine self-administration was significantly higher in HiS LgA rats, compared to LoS LgA rats. HiS rats responded on the cocaine-paired lever more than LoS rats during maintenance, extinction, and cocaine-(15 mg/kg) induced reinstatement. CONCLUSIONS: These results suggest that HiS and LoS rats have distinct drug-seeking and drug-taking profiles. The HiS and LoS rats differ along a wide range of behavioral dimensions and represent an important model to study the interactions of excessive intake of dietary substances and vulnerability to drug abuse.

Binding of warfarin influences the acid-base equilibrium of H242 in sudlow site I of human serum albumin.

Sudlow Site I of human serum albumin (HSA) is located in subdomain IIA of the protein and serves as a binding cavity for a variety of ligands. In this study, the binding of warfarin (W) is examined using computational techniques and isothermal titration calorimetry (ITC). The structure of the docked warfarin anion (W-) to Site I is similar to that revealed by X-ray crystallography, with a calculated binding constant of 5.8 x 10(5) M(-1). ITC experiments (pH 7.13 and I = 0.1) carried out in three different buffers (MOPs, phosphate and Tris) reveal binding of W- is accompanied by uptake of 0.30+/-0.02 protons from the solvent. This measurement suggests that the binding of W- is stabilized by an ion-pair interaction between protonated H242 and the phenoxide group of W-.

Sex differences in physical dependence on orally self-administered phencyclidine (PCP) in rhesus monkeys (Macaca mulatta).

Withdrawal from orally self-administered phencyclidine (PCP) has been shown to alter operant baselines of food-maintained responding. The goal of the present study was to determine whether there are sex differences in these alterations. Seven female and 7 male rhesus monkeys (Macaca mulatta) were given concurrent access to PCP and water under fixed ratio (FR) 8 schedules during 2 daily sessions that alternated with 2 sessions during which pellet deliveries were contingent on lever presses under an FR 64 schedule. After operant responding stabilized, PCP was replaced by water for 10 days, and food access remained under the same schedule. Subsequently, concurrent PCP and water access was reintroduced for 10 days. This procedure was repeated with 3 PCP concentrations (0.125, 0.25, and 0.50 mg/ml) and 3 FR requirements for food-reinforced responding (64, 128, and 256). Disruptions in operant responding for food served as a quantitative measure of withdrawal severity. During PCP withdrawal, males showed a greater suppression of food-maintained behavior than females at the 2 highest PCP concentrations and the lowest FR requirement tested. Males responded more than females for PCP; however, when weight was taken into consideration, PCP intake (milligrams per kilogram) in males and females was equal. The data suggest that males may experience more severe withdrawal effects than females, and the duration of the adverse effects of withdrawal lasts longer in males than in females. This study is the 1st to use nonhuman primates to document sex differences in withdrawal severity as measured by a quantifiable baseline.

Impulsivity (delay discounting) as a predictor of acquisition of IV cocaine self-administration in female rats.

RATIONALE: Previous research in humans suggests a relationship between drug abuse and impulsivity as shown by selection of a smaller immediate reward over a larger delayed reward. However, it is not clear whether impulsivity precedes drug abuse or drug abuse influences impulsivity. OBJECTIVE: The hypothesis of the present experiment was that rats selected for choosing smaller, immediate over larger, delayed food would acquire IV cocaine self-administration faster than those choosing larger, delayed food rewards. METHODS: Female rats were screened for locomotor activity and trained on a delay discounting procedure that allowed them access to two response levers and a food pellet dispenser. Under a fixed-ratio (FR) 1 schedule, responding on one lever resulted in immediate delivery of one 45 mg pellet, while responding on the other lever resulted in delivery of three 45 mg pellets after a variable delay that increased after responses on the delay lever and decreased after responses on the immediate lever. For each rat, a mean adjusted delay (MAD) was calculated for each daily session, and stability was defined as MADs varying less than 5 s across 5 days. Based on their average MADs, rats were separated into low impulsive (LoI) and high impulsive (HiI) groups, implanted with an indwelling IV catheter, and trained to lever press for cocaine (0.2 mg/kg) under an FR1 schedule. RESULTS: There were no differences in locomotor activity between the LoI and HiI groups; however, a greater percentage of the HiI group acquired cocaine self-administration, and they did so at a significantly faster rate than the LoI rats. CONCLUSIONS: Performance on the delay discounting model of impulsivity predicted vulnerability to subsequent acquisition of cocaine self-administration.

Autonomic Imbalance as a Predictor of Metabolic Risks, Cardiovascular Disease, Diabetes, and Mortality.

CONTEXT: Identifying novel early predictors of metabolic disorders is essential to improving effective primary prevention. OBJECTIVES: The objectives were to examine the contribution of two measures of autonomic imbalance, resting heart rate (RHR) and heart rate variability (HRV), on the development of five metabolic risk outcomes, and on cardiovascular disease, diabetes, and early mortality. DESIGN: This study was a secondary analysis of prospective data from Offspring Cohort participants (N = 1882) in the Framingham Heart Study (FHS). PARTICIPANTS: Participants at FHS Exam 3 (1983-1987) with 1) age years 18 or older, and 2) data on RHR, HRV, and five measures of metabolic risk (blood pressure, fasting glucose, triglycerides, high-density lipoprotein [HDL] cholesterol, and body mass index [BMI]) at three follow-up visits over 12 years. We conducted a backward elimination variable selection procedure on a logistic regression model, using baseline RHR, HRV, age, sex, and smoking status to predict the odds of developing a specific metabolic risk. OUTCOMES: Measures included hyperglycemia, high blood pressure, high triglycerides, low HDL cholesterol, and high BMI over 12 years; incident diabetes, cardiovascular disease, and early mortality over 20 years. RESULTS: RHR and HRV, along with sex, age, and smoking were significant predictors of high blood pressure, hyperglycemia, and a diagnosis of diabetes within 12 years. RHR and HRV also predicted the development of cardiovascular disease and early mortality for most of the sample. CONCLUSIONS: In this community sample two measures of autonomic imbalance predicted multiple poor metabolic outcomes and mortality, making autonomic imbalance a potentially worthy target for intervention studies to reduce risks for cardiovascular disorders, diabetes, and early death.

The anti-(+)-methamphetamine monoclonal antibody mAb7F9 attenuates acute (+)-methamphetamine effects on intracranial self-stimulation in rats.

Passive immunization with monoclonal antibodies (mAbs) against (+)-methamphetamine (METH) is being evaluated for the treatment of METH addiction. A human/mouse chimeric form of the murine anti-METH mAb7F9 has entered clinical trials. This study examined the effects of murine mAb7F9 on certain addiction-related behavioral effects of METH in rats as measured using intracranial self-stimulation (ICSS). Initial studies indicated that acute METH (0.1-0.56 mg/kg, s.c.) lowered the minimal (threshold) stimulation intensity that maintained ICSS. METH (0.3 mg/kg, s.c.) also blocked elevations in ICSS thresholds (anhedonia-like behavior) during spontaneous withdrawal from a chronic METH infusion (10 mg/kg/day x 7 days). In studies examining effects of i.v. pretreatment with mAb7F9 (at 30, 100, or 200 mg/kg), 200 mg/kg blocked the ability of an initial injection of METH (0.3 mg/kg, s.c.) to reduce baseline ICSS thresholds, but was less capable of attenuating the effect of subsequent daily injections of METH. MAb7F9 (200 mg/kg) also produced a small but significant reduction in the ability of METH (0.3 mg/kg, s.c.) to reverse METH withdrawal-induced elevations in ICSS thresholds. These studies demonstrate that mAb7F9 can partially attenuate some addiction-related effects of acute METH in an ICSS model, and provide some support for the therapeutic potential of mAb7F9 for the treatment of METH addiction.

Interaction of ochratoxin A with human serum albumin. Binding sites localized by competitive interactions with the native protein and its recombinant fragments.

Competitive interactions of ochratoxin A (OTA) and several other acidic compounds were utilized to gain insight into the localization of binding sites and the nature of binding interactions between anionic species and human serum albumin (HSA). Depolarization of OTA fluorescence in the presence of a competing anion was used to quantify ligand-protein interactions. The results obtained were rationalized in terms of OTA displacement from its major binding site. Based on their ability to displace OTA, two distinct groups of the anionic ligands were revealed. The first group contained structurally diverse compounds that shared a common binding site in subdomain IIA (Sudlow Site I). The second group consisted of three non-steroidal anti-inflammatory drugs, which showed much lower affinity to Site I than the OTA dianion. The major site for these drugs was located in domain III. Fluorescence spectroscopy measurements of OTA, warfarin (WAR) and naproxen (NAP) complexes with recombinant proteins corresponding to the domains of HSA (D1-D3) revealed binding to all domains but with different affinities. The binding constants for OTA and WAR decreased in the series D2z.Gt;D3>D1. In contrast, NAP showed the most favorable interaction with D3 and comparable affinities to the two remaining domains. The OTA binding constant for D2, 7.9 x 10(5) M(-1), was smaller than the largest constant for HSA by a factor of approximately 7. The binding constant for OTA with D3, 1.1 x 10(5) M(-1), was very close to that of the secondary binding site for HSA.

Role of medial prefrontal and orbitofrontal monoamine transporters and receptors in performance in an adjusting delay discounting procedure.

Performance in an adjusting delay discounting procedure is predictive of drug abuse vulnerability; however, the shared underlying specific prefrontal neural systems linking delay discounting and increased addiction-like behaviors are unclear. Rats received direct infusions of methylphenidate (MPH; 6.25, 25.0, or 100µg), amphetamine (AMPH; 0.25, 1.0, or 4.0µg), or atomoxetine (ATO; 1.0, 4.0, or 16.0µg) into either medial prefrontal cortex (mPFC) or orbitofrontal cortex (OFC) immediately prior to performance in an adjusting delay task. These drugs were examined because they are efficacious in treating impulse control disorders. Because dopamine (DA) and serotonin (5-HT) receptors are implicated in impulsive behavior, separate groups of rats received microinfusions of the DA receptor-selective drugs SKF 81297 (0.1 or 0.4µg), SCH 23390 (0.25 or 1.0µg), quinpirole (1.25 or 5.0µg), and eticlopride (0.25 or 1.0µg), or received microinfusions of the 5-HT receptor-selective drugs 8-OH-DPAT (0.025 or 0.1µg), WAY 100635 (0.01 or 0.04µg), DOI (2.5 or 10.0µg), and ketanserin (0.1 or 0.4µg). Impulsive choice was not altered significantly by MPH, AMPH, or ATO into either mPFC or OFC, indicating that neither of these prefrontal regions alone may mediate the systemic effect of ADHD medications on impulsive choice. However, quinpriole (1.25µg) and eticlopride infused into mPFC increased impulsive choice, whereas 8-OH-DPAT infused into OFC decreased impulsive choice. These latter results demonstrate that blockade of DA D2 receptors in mPFC or activation of 5-HT1A receptors in OFC increases impulsive choice in the adjusting delay procedure.

Prefrontal cortex and drug abuse vulnerability: translation to prevention and treatment interventions.

Vulnerability to drug abuse is related to both reward seeking and impulsivity, two constructs thought to have a biological basis in the prefrontal cortex (PFC). This review addresses similarities and differences in neuroanatomy, neurochemistry and behavior associated with PFC function in rodents and humans. Emphasis is placed on monoamine and amino acid neurotransmitter systems located in anatomically distinct subregions: medial prefrontal cortex (mPFC); lateral prefrontal cortex (lPFC); anterior cingulate cortex (ACC); and orbitofrontal cortex (OFC). While there are complex interconnections and overlapping functions among these regions, each is thought to be involved in various functions related to health-related risk behaviors and drug abuse vulnerability. Among the various functions implicated, evidence suggests that mPFC is involved in reward processing, attention and drug reinstatement; lPFC is involved in decision-making, behavioral inhibition and attentional gating; ACC is involved in attention, emotional processing and self-monitoring; and OFC is involved in behavioral inhibition, signaling of expected outcomes and reward/punishment sensitivity. Individual differences (e.g., age and sex) influence functioning of these regions, which, in turn, impacts drug abuse vulnerability. Implications for the development of drug abuse prevention and treatment strategies aimed at engaging PFC inhibitory processes that may reduce risk-related behaviors are discussed, including the design of effective public service announcements, cognitive exercises, physical activity, direct current stimulation, feedback control training and pharmacotherapies. A major challenge in drug abuse prevention and treatment rests with improving intervention strategies aimed at strengthening PFC inhibitory systems among at-risk individuals.

Nicotine self-administration in the rat: effects of hypocretin antagonists and changes in hypocretin mRNA.

RATIONALE: The hypocretin (hcrt) system has been implicated in addiction-relevant effects of several drugs, but its role in nicotine dependence has been little studied. OBJECTIVES: These experiments examined the role of the hcrt system in nicotine reinforcement. METHODS: Rats were trained for nicotine self-administration (NSA) on fixed-ratio schedules. The effects of acute, presession treatments with the hcrtR1 antagonist SB334867 and the hcrtR1/2 antagonist almorexant were examined on NSA maintained on a fixed-ratio (FR) 5 schedule. Gene expression for the hcrt system (mRNA for hcrt, hcrtR1, and hcrtR2) was measured in animals following NSA on a FR 1 schedule for a 19-day period. RESULTS: The hcrtR1 antagonist SB334867 and the hcrtR1/2 antagonist almorexant both reduced NSA dose-dependently (significantly at doses of 30 and 300 mg/kg, respectively); SB334867 did not affect food-maintained responding whereas almorexant (at the 300 mg/kg) did. Tissue from animals collected 5 h after self-administration showed an increase in hcrtR1 mRNA in the arcuate nucleus compared to control subjects. In tissue collected immediately after a similar 19-day self-administration period, mRNA for hcrtR1 was decreased in the rostral lateral hypothalamus compared to controls. CONCLUSIONS: These data confirm a previous report (Hollander et al., Proc Natl Acad Sci U S A 105:19480-19485, 2008) that the hypocretin receptor hcrtR1 is activated in nicotine reinforcement and in addition show that both the arcuate nucleus and lateral hypothalamus are sites at which hcrt receptor mechanisms may influence reinforcement. Different patterns of mRNA expression at different times after NSA suggest that changes in the hcrt system may be labile with time.