Priming Infusion Research Articles

3294 HIGH INTENSITY BINGE DRINKING AND STIMULATING EFFECTS IN HUMAN LABORATORY STUDIES OF ALCOHOL SELF-ADMINISTRATION

OBJECTIVES/SPECIFIC AIMS: Alcohol use disorder (AUD) has previously been studied using Timeline Followback (TLFB) interview measures and administration of alcohol within laboratory sessions. However, most of those studies supplied alcohol orally and analyzed drinking across a range of drinking intensity and frequency measures. High intensity binge drinking, i.e., drinking alcohol at multiple levels of the binge threshold (5+ drinks for males, 4+ drinks for females) has been identified as a significant risk factor for developing AUD. In the present study, we examined the relationship between high intensity binge drinking with the behavioral and subjective response to intravenous alcohol in a lab study. METHODS/STUDY POPULATION: Two hundred participants completed a 90-Day TLFB interview, wherein the maximum number of drinks in a day established the participant’s binge level status as a Non-Binger (N = 37), Binge Level 1 (N = 96), Binge Level 2 (N = 44), or Binge Level 3 (N = 22). Binge Level 1 corresponds with at least one binge (4-7 drinks for women, 5-9 drinks for men); Binge Level 2 requires at least twice the binge level (8-11 drinks for women, 10-14 drinks for men); and Level 3 necessitates a participant to drink at least three times the binge level (12+ drinks for women, 15+ drinks for men) on one day. Non-Bingers had no binge level drinking in the 90-day interview. Participants also underwent a 150-minute intravenous-alcohol self-infusion, where participants would press a button to receive an infusion of an ethanol solution. During this, participants also completed subjective questionnaires including the Alcohol Urge Questionnaire (AUQ), Biphasic Alcohol Effects Scale (BAES), and Drug Effects Questionnaire (DEQ). Kruskal-Wallis and chi-square tests were used to examine the effect of group on alcohol infusion and subjective response measures. RESULTS/ANTICIPATED RESULTS: A chi-square test for association showed significant statistical differences by groups in reaching binge level status (0.08% breath alcohol content) during the alcohol infusion session in the lab, X2 (3) = 23.321, p < 0.001. However, mean difference was not significantly different between Binge Level 2 and Binge Level 3 (0 < 1 < 2 = 3). Binge level groups showed significant differences in the number of button presses during the lab session (H(3) = 36.955, p < 0.001), peak breath alcohol concentration in the lab session (H(3) = 19.870, p < 0.001), and total binges in the TLFB (H(3) = 90.296, p < 0.001). Increased self-administration measures were proportional to the binge intensity level across groups, with no differences between Binge Level 2 and Binge Level 3 (0 < 1 < 2 = 3). For subjective measures, a Kruskal-Wallis H median test showed statistically significant differences between groups in the AUQ score following the priming infusion, H(3) = 11.489, p = 0.009, with bingers at all levels reporting higher scores compared to non-bingers (0 < 1 = 2 = 3). There was also a statistically significant difference between groups in the BAES Stimulation score following the priming infusion, H(3) = 9.023, p = 0.029, with differences seen between non-bingers and level 2 and level 3 bingers (0 = 1 < 2 = 3). DISCUSSION/SIGNIFICANCE OF IMPACT: This study demonstrated that high intensity binge drinkers were more likely to reach binge level and overall greater alcohol consumption during a human lab alcohol administration study. Binge intensity level was also associated with higher stimulation and urge for alcohol following priming exposures, which may in turn drive the consumption of greater amounts of alcohol, which we know to be associated with greater risk for AUD.

Contraception continuation among female exotic dancers seeking mobile reproductive health services concurrent with syringe exchange

s / Drug and Alcohol Dependence 140 (2014) e86–e168 e135 Contraception continuation among female exotic dancers seeking mobile reproductive health services concurrent with syringe exchange Caitlin E. Martin1, Mishka Terplan2, J. Han3, P. Chaulk4, C. Serio-Chapman3 1 Johns Hopkins Schools of Medicine and Public Health, Baltimore, MD, United States 2 Departments of Obstetrics, Gynecology, and Reproductive Sciences & Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD, United States 3 Community Risk Reduction Services, Baltimore City Health Department, Baltimore, MD, United States 4 Bureau of HIV/STD Services, Baltimore City Health Department, Baltimore, MD, United States Aims: Female exotic dancers are an understudied population with a high prevalence of drug and alcohol use, risk factors for transactional sex and inconsistent condom use. In 2009, the Baltimore City Health Department expanded their mobile syringe exchange program to include reproductive health services in the “Red Light” district. The objective of this study was to describe depot medroxyprogesterone acetate (Depo-Provera) continuation patterns among female exotic dancers seeking these mobile health services. Methods: We performed a retrospective analysis of 75 clients who initiated Depo-Provera at a mobile health clinic attached to a syringe exchange from November 2009 to August 2012. Demographics, Depo-Provera uptake and continuation over 12 months were assessedby chart review. Characteristics between clientswho continued Depo-Provera at 3 months and those who did not were compared using chi-square and t-tests. Results: Seventy-two percent (N=52) of clients were African American, and 62% (N=42) were 24 years or younger. At 3 months, 36% (N=25) continued Depo-Provera. Clients who were Caucasian (p=0.03) and received other reproductive health services (p<0.01) were more likely to continue. At 6 and 12 months, 29% and 7% of all clients who initiated Depo-Provera continued, while successive continuation rates for those receiving the previous injection were higher at 54% and 63%. Conclusions: Continuation of Depo-Provera among female exotic dancers is similar to that of the general population, with low overall but higher successive continuation after 3 months. Our study illustrates that integrating mobile reproductive health services into a needle exchange program can help fulfill the unique health needs of this high-risk population. Financial support: None. http://dx.doi.org/10.1016/j.drugalcdep.2014.02.383 9-tetrahydrocannabinol does not substitute in rats trained to self-administer WIN55212-2 Julie A. Marusich, T. Lefever, J. Wiley Discovery & Analytical Sciences, RTI International, Research Triangle Park, NC, United States Aims: Although THC i.v. self-administration has been demonstrated in nonhuman primates, establishing THC selfadministration in rodents has proven difficult. In contrast, self-administration of a synthetic cannabinoid, WIN55212-2 (WIN), in rats has been reported. The purpose of this study was to examine if rats trained to self-administer WIN would also self-administer THC. Methods: Male Long-Evans rats were trained to self-administer cocaine (COC; 0.03mg/kg/infusion) or WIN (0.01mg/kg/infusion) through autoshaping. Rats were thenmaintained on a fixed ratio 3, with 3 priming infusions given at the beginning of each 3h session. Dose-effect curves of the training drugs were assessed followed by pretreatment with rimonabant. Dose–effect curves were then determined for WIN in the COC group, and THC in the WIN group. Results: Rats self-administered COC and WIN at levels significantly above vehicle. Rimonabant decreased responding for both drugs. When WIN was substituted for COC, rats did not acquire self-administration of WIN. Similarly when THC was substituted for WIN, rats did not acquire self-administration of THC. Conclusions: Themethodsusedhereproduced similar amounts of WIN intake compared to previous studies in rats; however, THC did not substitute for WIN. Between subject variability was high for both WIN and THC. Given the typical within class substitution observed in previous self-administration studies, these results suggest that the reinforcing effects of WIN and THC differ in rats. In previous research, establishing self-administration of other drug classes (e.g. stimulants) has also been largely unsuccessful in producing THC self-administration. Similarly, in the present study rats with a history of COC self-administration did not self-administer WIN, suggesting that exposure to a more reinforcing drug may decrease the likelihood of self-administration of cannabinoids, or that substitution across drug classes is not a reliable method for assessing abuse liability for cannabinoids. Financial support: RTI International internal research and development funds and NIDA Grants DA-03672 and DA-031988. http://dx.doi.org/10.1016/j.drugalcdep.2014.02.384 Binge alcohol consumption in emerging adults: Altered anterior cingulate cortical thickness is associated with alcohol use consequences Yasmin Mashhoon1,3,4, C. Czerkawski2, D.J. Crowley1,2,4, J.E. Cohen-Gilbert1,2,4, J.T. Sneider1,2,4, M.M. Silveri1,2,4 1 McLean Imaging Center, McLean Hospital/HMS, Belmont, MA, United States 2 Neurodevelopmental Lab, McLean Hospital/HMS, Belmont, MA, United States 3 Behavioral Psychopharmacology Research Lab, McLean Hospital/HMS, Belmont, MA, United States 4 Psychiatry, Harvard Medical School, Boston, MA,

Access to a running wheel inhibits the acquisition of cocaine self-administration

Physical activity decreases cocaine self-administration in laboratory animals and is associated with positive outcomes in substance abuse treatment programs; however, less is known about its efficacy in preventing the establishment of regular patterns of substance use in drug-naive individuals. The purpose of the present study was to examine the effects of access to a running wheel on the acquisition of cocaine self-administration in experimentally naive rats. Male, Long–Evans rats were obtained at weaning and assigned to sedentary (no wheel) or exercising (access to wheel) conditions immediately upon arrival. After six weeks, rats were surgically implanted with intravenous catheters and placed in operant conditioning chambers for 2h/day for 15 consecutive days. Each session began with a noncontingent priming infusion of cocaine, followed by a free-operant period in which each response on the active lever produced an infusion of cocaine on a fixed ratio (FR1) schedule of reinforcement. For days 1–5, responding was reinforced with 0.25mg/kg/infusion cocaine; for days 6–15, responding was reinforced with 0.75mg/kg/infusion cocaine. In addition, all rats were calorically restricted during days 11–15 to 85% to 95% of their free-feeding body weight. Compared to sedentary rats, exercising rats acquired cocaine self-administration at a significantly slower rate and emitted significantly fewer active lever presses during the 15days of behavioral testing. These data indicate that access to a running wheel inhibits the acquisition of cocaine self-administration, and that physical activity may be an effective intervention in substance abuse prevention programs.

CP-154,526, a CRF type-1 receptor antagonist, attenuates the cue-and methamphetamine-induced reinstatement of extinguished methamphetamine-seeking behavior in rats

Previous studies from our laboratory and others have indicated a role for the hypothalamo-pituitary-adrenal (HPA) axis in the extinction/reinstatement animal model of cocaine relapse This present study was designed to investigate the potential role for the HPA axis in the cue- and methamphetamine-induced reinstatement of extinguished methamphetamine-seeking behavior by determining the effects of ketoconazole and the corticotropin-releasing hormone (CRF) type 1 receptor antagonist, CP-154,526, on these behaviors. Male Wistar rats were trained to self-administer methamphetamine (0.03 mg/kg/infusion). The delivery of methamphetamine was paired with the presentation of a tone and the illumination of a house light. Once stable responding was reached, the rats were placed into extinction. The effects of pretreatment with ketoconazole (25, 50, or 100 mg/kg, i.p.) or CP-154,526 (20 or 40 mg/kg, i.p.; 3 micro g, i.c.v) on cue-induced reinstatement were then evaluated. Cue-induced reinstatement was not significantly attenuated by pretreatment with peripherally administered CP-154,526 or by pretreatment with ketoconazole. However, centrally administered CP-154,526 (3 micro g, i.c.v.) significantly attenuated cue-induced reinstatement. In a separate group of rats, CP-154,526 (20 mg/kg, i.p.) attenuated methamphetamine-induced reinstatement (0.12 mg/kg priming infusion); whereas a higher dose (40 mg/kg) was necessary to attenuate reinstatement induced by a priming infusion of 0.24 mg/kg/infusion. Ketoconazole (50 mg/kg) did not affect reinstatement induced by a 0.12 mg/kg priming infusion and, therefore, was not tested at the higher methamphetamine priming dose. These data suggest an important role for CRF in the cue- and methamphetamine-induced reinstatement of extinguished methamphetamine-seeking behavior.

"Waste Not, Want Not": Determining the Optimal Priming Volume for Intravenous Insulin Infusions

Insulin adsorbs to plastics used for intravenous (IV) tubing. As a result, clinical IV insulin infusion procotols advise an initial priming volume of up to 50 mL, which may be wasteful-especially since most institutions use 100-mL IV solution bags. In this brief report, we sought to determine the optimal priming volume required for clinical IV insulin infusions. One hundred units of regular human insulin was dissolved into 100 mL of 0.9% NaCl. Employing a standard polypropylene infusion set, a priming infusion was started. At 10- mL intervals, from 0 to 50 mL, effluent was collected directly into glass vials. After dilution (1:10,000) using a proprietary buffer, insulin concentrations were then measured using a double antibody radioimmunoassay. Twenty individually prepared insulin bags were tested in this manner. Insulin levels without prime were 15.8% [95% confidence interval (CI), 9.1-22.6%] lower than insulin levels following 50 mL of prime (designated as "maximal values"). After a priming volume of 10 mL, insulin adsorption losses fell to a marginally significant 6.6% (95% CI, 0.1-13.1%). Following 20 mL of prime, insulin concentrations were indistinguishable from maximal values (3.4% loss, 95% CI, -0.2% to 7.1%). For standard IV insulin infusions, a priming volume of 20 mL is sufficient to minimize the effect of insulin adsorption losses to IV lines. Priming volumes exceeding 20 mL are wasteful, increase costs, and generate unnecessary work for nurses and pharmacists.

Elimination of fat emulsion particles from plasma during glucose infusion.

To determine the optimal rate of infusion of a fat emulsion (long-chain triglycerides; LCTs) for parenteral nutrition, the rate of elimination of triglycerides from plasma was measured on two occasions in three healthy subjects, once while receiving LCTs alone (study I) and once while receiving a combined infusion of glucose and LCTs (study 2). In study 1 a hypertriglyceridaemic clamp was set up by raising the concentration of triglycerides to 2 mmol l(-1) (60-min priming infusion at 0.2 g LCTs per kg body-weight per h) and maintaining this value for 300 min. In study 2 a constant infusion of glucose at a rate of 0.32 g per kg body-weight per h was given throughout the 420-min test, and the hypertriglyceridaemic clamp was set up after 70 min. The infusion of glucose induced a progressive increase in the mean(s.d.) concentration of insulin from 4.3(0.4) microU ml(-1) to a plateau value of 11.0(0.2) microU ml(-1) which was sustained during the last 310 min of the study. During the steady state of the hypertriglyceridaemic clamp, the concentration of triglycerides (2.16(0.17) versus 2.12(0.20) mmol l(-1), P = 0.26), as well as the mean(s.d.) rates of infusion of LCTs (0.12(0.08) versus 0.12(0.04) per kg body-weight per h, P = 0.38), did not differ between studies 1 and 2. Thus, an infusion of glucose (and the associated physiological increase in the concentration of insulin) at doses commonly used in parenteral nutrition does not influence the rate of elimination of triglycerides from plasma in normal subjects.

Extinction of Cocaine Self-Administration Reveals Functionally and Temporally Distinct Dopaminergic Signals in the Nucleus Accumbens

While Pavlovian and operant conditioning influence drug-seeking behavior, the role of rapid dopamine signaling in modulating these processes is unknown. During self-administration of cocaine, two dopaminergic signals, measured with 100 ms resolution, occurred immediately before and after the lever press (termed pre- and post-response dopamine transients). Extinction of self-administration revealed that these two signals were functionally distinct. Pre-response transients, which could reflect the motivation to obtain the drug, did not decline during extinction. Remarkably, post-response dopamine transients attenuated as extinction progressed, suggesting that they encode the learned association between environmental cues and cocaine. A third type of dopamine transient, not time locked to overt stimuli, decreased in frequency during extinction and correlated with calculated cocaine concentrations. These results show that dopamine release transients involved in different aspects of cocaine self-administration are highly plastic--differentially governed by motivation, learned associations linked with environmental stimuli, and the pharmacological actions of cocaine.

Reinstatement of nicotine self-administration in rats by presentation of nicotine-paired stimuli, but not nicotine priming

The objective of the present study was to determine the relative efficacy of nicotine priming and nicotine-paired stimuli in reinstating extinguished NSA in rats. The relative efficacy of different stimulus conditions in reinstating NSA was also determined. Rats were trained to self-administer nicotine (0.03 mg/kg/inf) under an FR 5 schedule. Onset of a light above the active lever was correlated with nicotine availability, while offset of the light was paired with each nicotine infusion. In Experiment 1, saline extinction was arranged in the presence of these light stimuli. After extinction criteria were met, the effects of priming doses of nicotine (0.01, 0.03. and 0.06 mg/kg/inf, i.v.) on active lever pressing were determined. In Experiment 2, extinction of NSA was arranged in the absence of the light stimuli. After extinction criteria were met, reinstatement sessions were arranged involving either (1) a priming infusion of nicotine (0.03 mg/kg), (2) presentation of the same light stimuli as during NSA training, (3) constant illumination of the cue light, or (4) a combination of a nicotine priming infusion with one of the stimulus-light conditions. In Experiment 1, nicotine generally failed to reinstate NSA at any priming dose. In Experiment 2, both stimulus conditions reinstated NSA, with the stimulus condition identical to training producing a greater effect. Nicotine priming alone failed to significantly reinstate NSA. Nicotine priming combined with either stimulus condition was no more effective than each stimulus condition alone in reinstating NSA. These findings suggest that nicotine-paired cues are more effective than nicotine alone in reinstating extinguished NSA and are consistent with other studies showing that nicotine-paired stimuli play an important role in the reacquisition of NSA.

Hyperproinsulinaemia in impaired glucose tolerance is associated with a delayed insulin response to glucose.

In subjects with impaired glucose tolerance hyperproinsulinaemia has been shown to be predictive for progression to Type II (non-insulin-dependent) diabetes mellitus. These findings are often interpreted as early indicators of an impaired beta-cell function. The aim of our study was to assess the potential determinants of hyperproinsulinaemia in subjects with impaired glucose tolerance. The study group consisted of 110 subjects, 45-74 years of age with mean 2 h plasma glucose concentrations between 8.6 and 11.1 mmol/l following two oral glucose tolerance tests. Subsequently, the hyperglycaemic clamp technique (10 mmol/l, with a priming infusion of 20% glucose solution, 150 mg/kg) was used to assess the beta-cell function (time needed to reach the insulin peak) and insulin sensitivity (M/I value: glucose metabolised divided by insulin response, 150-180 min). Results showed that the intact-proinsulin:insulin ratio increased with increasing time needed to reach the insulin peak (0.065, 0.079 and 0.101; time needed to reach the insulin peak < or = 5 min, 5 to 15 min, > 15 min; p < 0.05). The split-proinsulin:insulin ratio showed a similar association with the time needed to reach the insulin peak. These associations were independent of age, sex, body mass index and waist:hip ratio. In conclusion, this study shows that relative hyperproinsulinaemia is associated with an impaired beta-cell function in a study group of subjects with impaired glucose tolerance selected after two oral glucose tolerance tests.

THE RELIABILITY OF THE HYPERINSULINEMIC/EUGLYCEMIC CLAMP IN ACTIVE HEALTHY ADULTS.

1394 Although the hyperinsulinemic/euglycemic clamp (HEC) is a commonly-used procedure, published reliability data are scarce. We tested the reliability of the 2-hr HEC in three younger (22±1y) and one older (73 y) healthy, active adults over three serial clamp procedures, spaced 4 weeks apart. Each clamp was preceded by 3 days of no exercise and a diet consisting of >150 gm carbohydrates· day-1, plus an overnight stay in the hospital. Following a 12-hr overnight fast, insulin was infused at a rate of 40 m U· m-2· min-1 for 110 min after a 10-min priming infusion. Plasma glucose concentrations were determined every 5 min, and the glucose (20% dextrose) infusion rate adjusted as necessary to clamp plasma glucose at 100 mg· dL-1 during hyperinsulinemia. Total-body glucose disposal rate (M) was calculated from the average glucose infusion rate during the final 60 min of the clamp, after correcting for changes in the glucose pool sizes. The average M among the younger adults was 8.1 and in the older adult was 3.2 mg· kg-1· min-1, confirming the existence of insulin resistance in the older adult. The within-subject coefficients of variation among the three clamps were 0.05, 0.09, and 0.05 for the three younger people and 0.12 for the older woman. We conclude that this procedure is highly reliable for both younger and older people and is quite sensitive for identifying aging-related difference in glucose disposal.

Constant infusion rates of lipid emulsions to stabilize plasma triglyceride concentrations: medium-chain triglyceride/long-chain triglyceride emulsions (MCT/LCT) versus LCT.

As medium-chain triglyceride emulsions (MCT) are more rapidly hydrolyzed than long-chain triglyceride emulsions (LCT), MCT/LCT tends to be infused faster than LCT. The purpose of the present study was to determine the most appropriate infusion rate for MCT/LCT to stabilize plasma concentrations of triglyceride (TG), being equivalent to the optimal infusion rate of the emulsion. A TG clamp was set up by raising the mean +/- SD concentrations of TG in plasma, being 1.08 +/- 0.18 delta mmol l(-1) for LCT, and 1.65 +/- 0.31 delta mmol l(-1) for MCT/LCT after a 50-min priming infusion of each emulsion. Thereafter, the infusion rate of lipid was controlled every 10 min to maintain a steady concentration of TG for a period of 150 min. A constant infusion of glucose at 0.32 g/kg body weight (BW) per h was administered for the test period. The weight-based rate of the infusion to maintain a steady state of plasma TG concentrations did not differ between MCT/LCT and LCT, being 0.125 +/- 0.013 vs 0.117 +/- 0.021 g/kg BW per h, while the molar-based infusion rate was 0.203 +/- 0.021 mmol/kg BW per h for MCT/LCT and 0.132 +/- 0.023 mmol/kg BW per h for LCT (P < 0.05). These results suggest that although 54% more molar MCT/LCT-TG can be hydrolyzed during a constant infusion, MCT/LCT should not be infused at a rate faster than 0.1 g/kg BW per h under a steady state.

Excitotoxic lesions of the basolateral amygdala impair the acquisition of cocaine-seeking behaviour under a second-order schedule of reinforcement

In these experiments we sought to establish the intravenous (i.v.) self-administration of cocaine under a second-order schedule of reinforcement in order: (i) to obtain reliable, drug-free levels of responding with cocaine as a reinforcer, and (ii) to enable investigation of the neural mechanisms by which arbitrary cues gain motivational salience and, as conditioned reinforcers, control over drug-seeking behaviour. Initially, each infusion of cocaine was made contingent upon a response on one of two identical levers and was paired with a 20-s light conditioned stimulus (CS). Responses on the second lever were recorded, but had no programmed consequence. When rats acquired stable rates of self-administration, a second-order schedule of the type FRx(FRy:S) was introduced, with values of "x" being increased progressively to 10 and then "y" from 2 through 8. Priming (i.e. non-contingent) infusions of cocaine were never given. Once the first infusion was obtained under the second-order schedule, further infusions were made contingent on each response (to a maximum of ten infusions/day). Each stage was repeated daily until the first infusion of each session was achieved within a 5-min criterion. Rats with bilateral, excitotoxic lesions of the basolateral amygdala readily acquired the i.v. self-administration of cocaine under a continuous reinforcement schedule, initially administering more infusions and maintaining a slightly elevated level of self-administration than controls. Despite increased numbers of CS/drug pairings, basolateral amygdala-lesioned rats were severely impaired in the acquisition of the second-order schedule of i.v. cocaine reinforcement. Lesioned rats showed a cocaine dose-response function that was shifted upwards relative to control subjects. There was no significant difference between drug-naive amygdala-lesioned and control animals in the locomotor response to intraperitoneal injections of cocaine. These experiments indicate the feasibility and utility of second-order schedules in studying the neurobehavioural basis of cocaine-seeking behaviour. They suggest a dissociation in the neural mechanisms underlying cocaine-taking and cocaine seeking behaviour, and demonstrate the potential importance of the basolateral amygdala in the processes by which previously neutral stimuli gain control over drug-seeking behaviour.

Nicotine reinstatement of nicotine self-administration after long-term extinction.

The effect of non-contingent priming injections of nicotine on the reinstatement of drug-seeking behaviour was studied in rats following the long-term extinction of nicotine self-administration. Male rats were trained to lever press for 0.03 mg/kg per infusion of intravenous nicotine. Nicotine maintained a robust self-administration behaviour (11.5 +/- 1.2; mean+/-SEM infusions/1-h session). When nicotine availability was discontinued, and only a non-contingent saline infusion was presented to the experimental subjects at the beginning of each daily session, responding for the drug-paired lever decreased to low values. After 4-13 sessions, responding extinguished. During this "extinction" period, non-contingent priming infusions of nicotine 0.001, 0.003, 0.01 or 0.03 mg/kg per infusion induced reinstatement of responding for the drug-paired lever. The increased responding, compared with the corresponding previous day on saline, was observed at all four nicotine doses but was not statistically significant for the higher priming dose (0.03 mg/kg per infusion). These preliminary results indicate that nicotine priming is able to induce reinstatement of drug-seeking behaviour in rats similarly to other reinforcing drugs. The present findings show analogies with similar phenomena described in ex-smokers and support the addictive role of nicotine in tobacco smoking.

Elimination rate of fat emulsion particles from plasma in Japanese subjects as determined by a triglyceride clamp technique

The elimination rate of emulsion triglyceride (TG) from plasma was investigated in Japanese subjects by a plasma TG clamp technique. Two different studies were performed. In Study 1, a lipid emulsion (20% long-chain triglyceride emulsion: LCT) was infused into a healthy research associate to achieve a certain concentration of TG in the plasma. Thereafter, the infusion rate was adjusted to maintain the chosen concentrations of TG in plasma (namely, 4–5 mmol/L, 3–4 mmol/L, and approximately 2 mmol/L) over a period of 160 min by measuring plasma TG concentrations at 10-min intervals. Concentrations of TG in plasma were clamped within 2.13 ± 0.13 mmol/L by an infusion rate of 0.10 g·kg −1·h −1, within 3.34 ± 0.20 mmol/L by an infusion rate of 0.14 g·kg −1·h −1, and within 4.46 ± 0.22 mmol/L by an infusion rate of 0.11 g·kg −1·h −1. The mean rate of infusion of emulsified TG that had maintained the steady concentrations of TG in plasma was limited to the very narrow range of 0.12 ± 0.02 g of TG·kg −1·h −1 regardless of the chosen concentration of TG in plasma. Concentrations of nonesterified fatty acids (NEFA) also remained at a fixed level of 1.378 ± 0.103 mEq/L regardless of the chosen concentration of TG in the plasma. Study 2 was undertaken to determine whether plasma TG concentration reached a plateau during a period when emulsion TG was infused into three different subjects at a rate of 0.12 g·kg −1·h −1. The plasma TG concentrations were steady at a level of 2.04 ± 0.32 mmol/L, and the plasma NEFA concentrations remained at a fixed level of 1.33 ± 0.13 mEq/L, over a period of 160 min after 50-min priming infusion. These results indicate that the plasma TG elimination rate was limited to the narrow range of 0.12 ± 0.02 g·kg −1·h −1 when the fat emulsion was infused into Japanese subjects in a steady state. However, the plasma TG elimination rate in Japanese subjects appeared to be lower than that of Europeans. This may be due to a difference in lipoprotein lipase activity caused by different dietary habits, namely, a lower fat intake.

Stress reinstates heroin-seeking in drug-free animals: an effect mimicking heroin, not withdrawal.

Exposure to 10 min of footshock stress (1 mA; 0.5 s on, with a mean off period of 40 s) reinstated heroin-seeking behavior in heroin-experienced, drug-free rats after many sessions of extinction and up to 6 weeks after last exposure to heroin. In reinstating the behavior, the footshock mimicked the effect of a non-contingent priming infusion of heroin (50 micrograms/kg). By contrast, the aversive state of acute opioid withdrawal induced by injection of the opioid receptor antagonist naltrexone (5 mg/kg, SC), following an acute injection of morphine (10 mg/kg, SC), had no effect on heroin-seeking behavior. In a second experiment it was shown in drug naive animals that these parameters of footshock increased dopamine overflow in the nucleus accumbens, a terminal region of the mesolimbic dopamine system implicated in the reinforcing effects of drugs. Similarly, dopamine overflow was increased by an injection of 10 mg/kg morphine, SC, an effect that was reversed by an injection of 5 mg/kg naltrexone given 40 min after to induce the withdrawal condition. A possible interpretation of the present results is that stressors can reinstate drug-taking behavior by activating neural systems in common with those activated by heroin.

A simulation study to determine optimal insulin priming during glucose clamp studies

Computer simulation of hyperinsulinaemic euglycaemic clamp studies (HECS) using a novel model of insulin kinetics shows that a priming dose of insulin should be in the form of a 10-min-long infusion at a rate six-fold higher than the intended insulin infusion rate in patients with non-insulin-dependent diabetes mellitus. Using this priming regimen, glucose uptake attains equilibrium within 90 min. Two alternative priming regimens: a priming bolus and a monoexponential-decay priming infusion, also result in equilibrium of glucose uptake within 90 min, but give higher transients of plasma insulin concentration. However, with no priming, or if a conventional priming regimen is used, glucose uptake at 90 min rises to only around 80% of its equilibrium value. We conclude that priming of insulin is essential to attain steady state of glucose uptake within 90 min of HECS and that conventionally used priming regimens result in an underestimation of glucose uptake.

Fentanyl Plasma Concentrations Maintained by a Simple Infusion Scheme in Patients Undergoing Cardiac Surgery

The ability of a simple infusion scheme for fentanyl to achieve and maintain one of two target concentrations of fentanyl in plasma was studied in 17 patients having cardiac surgery that required the use of moderate hypothermic cardiopulmonary bypass (CPB). All patients received preanesthetic medication including morphine, a benzodiazepine, and/or scopolamine. Anesthesia was induced and maintained by one of two fentanyl infusion regimens: HIGH-FEN (n = 6), a priming infusion of 2.4 micrograms.kg-1 x min-1 for 20 min in combination with a continuous infusion of 0.3 microgram.kg-1.min-1 for the duration of the operation to produce a plasma fentanyl concentration of 20-25 ng/mL; or LOW-FEN (n = 11), priming and maintenance infusions of 2.4 and 0.15 micrograms.kg-1 x min-1 designed to produce a fentanyl concentration of 12-15 ng/mL of plasma. The six patients receiving HIGH-FEN had plasma fentanyl concentrations maintained between 20 and 27 ng/mL and none required anesthetic supplementation before CPB; one patient required a single dose of thiopental 50 mg after the termination of CPB. The total fentanyl dose for the operation (3.2 +/- 0.1 h) averaged 107 +/- 2 micrograms/kg (range 100.5-115.5 micrograms/kg). The 11 patients receiving LOW-FEN had a plasma fentanyl concentration maintained below 20 ng/mL (range 13-17 ng/mL). Eight patients before and 10 patients after CPB required anesthetic supplementation for adverse hemodynamic or somatic responses. For comparison purposes, another eight patients received a single 75 micrograms/kg dose of fentanyl during 20 min for induction of anesthesia, and 7 of the 8 required supplemental anesthetic agents before and after CPB.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of insulin infusion on capillary blood flow in the diabetic neuropathic foot.

The effect of a short-term improvement in glycaemic control induced by insulin infusion on foot skin capillary blood flow was previously unknown. In seven Type 2 (non-insulin-dependent) diabetic subjects with neuropathy capillary blood flow was measured in the great toe nailfold by television microscopy. An estimate of arteriovenous shunt flow was obtained simultaneously in the pulp of the great toe by laser Doppler flowmetry. After omission of oral hypoglycaemic therapy for 24 h mean blood glucose was 15.7 +/- 0.7 (SEM) mmol l-1. A priming infusion of 0.1 U kg-1 of insulin was given intravenously over 15 min, followed by a variable rate insulin infusion adjusted to steadily reduce blood glucose avoiding hypoglycaemia. At the end of the study blood glucose was reduced to 6.9 +/- 0.7 mmol l-1 (p less than 0.001). During the insulin infusion, capillary blood velocity increased by 28.8% (p less than 0.05), and the diameter of the capillary erythrocyte column increased from 7.6 +/- 0.2 to 9.2 +/- 0.3 micron (p less than 0.01). Thus during the insulin infusion, the calculated capillary flow increased to 226 +/- 36% above basal values (p less than 0.01). Laser Doppler flow did not change significantly, suggesting that during insulin infusion skin blood flow is redistributed with an increase in capillary flow relative to arteriovenous shunt flow.

Hypocalcemia induced by foscarnet (Foscavir) infusion in dogs

Foscarnet (Foscavir) is an antiviral drug for intravenous (iv) treatment of cytomegalovirus (CMV) retinitis in immunocompromised patients. The drug forms complexes with divalent metal ions such as Ca 2+ and serum calcium levels may be affected during its iv infusion. In this study, the effect on calcium homeostasis was investigated during daily 8-hr infusions of foscarnet in dogs. After priming infusions of 40 or 80 mg/kg administered during 0.5 hr, maintenance infusion rates were 46 or 91 mg/kg/hr (total daily doses of 410 or 810 mg/kg). At the low infusion rate, foscarnet was administered for 5 consecutive days. The mean plateau serum concentration was 0.56 mmol/liter and the main clinical sign was vomiting. Total serum calcium was reduced from about 2.5 to 2.0 mmol/liter and ionized calcium from 1.3 to 0.9 mmol/liter. Parathyroid hormone (PTH) levels in serum were elevated three to six times while calcitriol (1,25-(OH) 2D 3) levels were unaffected. At the high infusion rate, treatment was discontinued after 1–2 days of dosing due to pronounced adverse clinical signs such as extensive vomitings, apathy, ataxia, and muscle spasms. The mean serum plateau concentration of foscarnet at this dose level was 1.2 mmol/liter. Total serum calcium was reduced from 2.5 to 1.6 mmol/liter and ionized calcium from 1.3 to 0.7 mmol/liter. PTH as well as 1,25-(OH) 2D 3 levels in serum were elevated. Total and ionized calcium levels were normalized within 16 hr after stopping drug treatment. The results showed that foscarnet infusion affects calcium homeostasis and that calcium monitoring might be considered in the clinical use of the drug.

ALFENTANIL PLASMA CONCENTRATION v. EFFECT RELATIONSHIPS IN CARDIAC SURGICAL PATIENTS

Effects of alfentanil, preceded by lorazepam, on suppression of haemodynamic and somatic responses to noxious stimuli was studied in patients undergoing CABG. Plasma concentration of alfentanil, somatic and haemodynamic responses were measured at loss of consciousness, tracheal intubation, sternotomy and during multiple application of electrocoagulation. Additional alfentanil was administered i.v. to control unwanted responses. Study 1 (six patients): lorazepam 0.08 mg kg-1 by mouth 1-2 h before operation, alfentanil priming infusion (60 micrograms kg-1 min-1 for 10 min) followed by maintenance infusion (4.5 micrograms kg-1 min-1). With mean plasma alfentanil 1178 (SEM 54) ng ml-1, two patients required supplementary alfentanil to suppress somatic motor responses; one patients required nitroglycerin to control an increase in arterial pressure which was unresponsive to additional alfentanil following sternotomy. Study 2 (13 patients): lorazepam 0.04 mg kg-1 by mouth as premedication; one of three maintenance infusion rates of alfentanil: 5.4 (n = 4), 6.6 (n = 5), or 7.8 (n = 4) micrograms kg-1 min-1, each preceded by a proportional priming infusion. With plasma alfentanil 2181 (62) ng ml-1, somatic motor responses requiring additional alfentanil occurred in nine patients; haemodynamic responses in four of seven patients tested could not be controlled by alfentanil. The highest plasma concentration of alfentanil to prevent response to a stimulus other than tracheal intubation was different between the two studies (P less than 0.05). We conclude that alfentanil alone is insufficient to suppress haemodynamic and somatic motor responses to noxious stimulation during CABG and that the role of premedication is significant.