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At least 1,297 records · Page 72Linked to original sources
PubMed1990

Ethanol self-administration in long sleep and short sleep mice indicates reinforcement is not inversely related to neurosensitivity.

Studies of ethanol drinking suggest an inverse correlation between innate sensitivity to ethanol and behavior reinforced by this drug. The present study investigated ethanol reinforced behavior in mice selectively bred for high, Long Sleep/Institute for Behavioral Genetics (LS), and low, Short Sleep/Institute for Behavioral Genetics (SS), sensitivity to ethanol. Results show that both lines will drink large amounts of ethanol postprandially. However, in the absence of food presentation, LS and SS mice differed significantly in ethanol reinforced behavior. Ethanol maintained higher rates of responding, greater intake and higher blood ethanol levels in LS relative to SS mice across increasing fixed-ratio values. Ethanol did not maintain fixed-ratio lever pressing above rates maintained by vehicle in SS mice. Responding for and consumption of 8% ethanol significantly exceeded that of vehicle only in LS mice. Response rates of LS mice showed a typical inverted U-shaped relationship to ethanol concentration. Postsession blood ethanol levels and body temperatures indicated pharmacologically significant ethanol intake only in LS mice. Thus, ethanol served as an effective reinforcer in LS mice across a range of environmental conditions. Conversely, ethanol was not established as a positive reinforcer in SS mice under any of the broad range of conditions studied. These results are not consistent with the frequently reported negative correlation between ethanol intake and sensitivity to ethanol and rule out a causal basis for correlations seen between these traits.

Animals↗
PubMed1989

[Long-term results of primary hip total prosthesis with acetabulum reinforcement ring].

The Müller acetabular reinforcement ring has proven very useful, especially in total hip revision when the bone of the acetabulum is of poor quality or deficient. However, the acetabular reinforcement ring may also be indicated in primary total hip replacement, especially in the case of poor quality bone in the acetabular bone stock, e.g. in chronic polyarthritis or protrusio acetabuli, or of deficient morphology of the acetabulum, e.g. in hip dysplasia. We analysed the results recorded in 145 patients operated on between 1977 and April 1983. Each of these patients had received a total hip prosthesis for the first time, with the polyethylene cup supplemented by an acetabular reinforcement ring. This patient group cannot be compared with the usual patient populations reported on in connection with primary hip replacement, since most of our 145 patients had several risk factors and had undergone previous surgery on up to seven occasions on the hip ultimately replaced by a prosthesis. Radiological analysis did not show a significant correlation between malposition of the acetabular reinforcement ring and signs of loosening, except when the acetabular component had been implanted in a most atypical manner. The infection rate was 4.8%, but it must be borne in mind that from 1977 to 1983 there was no routine prophylaxis with antibiotics. The incidence of aseptic loosening of the acetabular reinforcement ring necessitating revision was 0.7% after a mean follow-up of 7.7 years (range 5.5-11 years).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetabulum↗
PubMed1980

[Preparation of carbon fiber reinforced fluid type resin denture (author's transl)].

Transverse strength of cured fluid resins is weaker than that of the heat cured. We have studied to improve the mechanical strength of self-cured acrylic resin by application of carbon fibers as reinforcement and simple methods which must be acceptable for technicians are proposed. A cloth type carbon fiber was the best reinforcement among studied carbon fibers such as chopped or mat. The chopped fibers were difficult to mix homogeneously with fluid resins and effectiveness of the reinforcement was low. Breaking often occurred at the interface between the reinforcement and resin in the cases of mat which gave defects to the test specimens. To prepare reinforced denture, the cloth was trimmed on the master cast after removal of wax and the prepreg was formed with the alginate impression on the cast by Palapress and the cloth. Other steps were same as the usual fluid resin.

Carbon↗
PubMed1994

Mesh reinforcement increases bursting strength of intestinal anastomoses in steroid-treated rabbits.

We tested the hypothesis that reinforcement of small bowel anastomoses with polyglycolic acid mesh (PGAM) would increase bursting strength in steroid-treated subjects. Twenty-two New Zealand white rabbits weighing 3-4 kg received methylprednisolone 0.2 mg/kg/day IM for 7-13 days preoperatively and until killed 4-5 days postoperatively. Steroid effect was confirmed by a 58.3 per cent decrease in absolute lymphocyte count and a histologic reduction in anastomotic fibroblast proliferation and collagen deposition. Two small bowel anastomoses were performed in each animal using standard two-layer suture technique. One of the two anastomoses, randomly assigned, was circumferentially reinforced with PGAM such that each animal served as its own control. Anastomotic bursting pressures, determined on postoperative Day 4-5, were significantly higher in mesh-reinforced anastomoses (P = 0.003). Histologic examination of the reinforced anastomoses revealed a well-developed layer of fibroblasts and collagen between the PGAM and bowel wall serosa. These results demonstrate that polyglycolic acid mesh reinforcement significantly increases the bursting strength of small bowel anastomoses in steroid-treated rabbits.

Anastomosis, Surgical↗
PubMed1995

The reinforcing effects of dopamine D1 receptor agonists in rhesus monkeys.

Central dopaminergic systems have been implicated in the reinforcing effects of a number of stimuli, including drugs of abuse; however, the role of dopamine D1 receptors remains controversial. The present study evaluated the reinforcing effects of six reportedly selective D1 agonists of differing intrinsic efficacies. Rhesus monkeys with chronic intravenous catheters lever pressed on a fixed-ratio 10 schedule maintained by a base-line cocaine dose of 0.03 mg/kg/inj in daily 1-hr sessions. Periodically, D1 agonists were substituted for the cocaine base-line. All monkeys (n = 4) self-administered the high-efficacy D1 agonists SKF 81297, SKF 82958 and R(+) 6-Br-APB at rates above those maintained by vehicle; therefore, each of these compounds functioned as a positive reinforcer (maxima: SKF 81297: 55-172 inj/hr, 0.01 mg/kg/inj; R(+) 6-Br-APB:103-165 inj/hr, 0.001 mg/kg/inj; SKF 82958: 110-149 inj/hr, 0.01 mg/kg/inj). In contrast, no monkeys self-administered the lower-efficacy D1 agonists SKF 38393 (N = 4), SKF 77434 (N = 4) or the S(-) enantiomer of 6-Br-APB (N = 2). Additionally, two stimulant-naive monkeys acquired self-administration of SKF 81297. The finding that selective D1 receptor agonists can function as positive reinforcers implicates D1 receptors in the reinforcing effects of psychomotor stimulants and of other drugs that stimulate D1 receptors.

Animals↗
PubMedDate not supplied

Influence of reinforcement design on the loss of marginal seal of provisional fixed partial dentures.

Loss of marginal cement seal, initial fracture, and stiffness of three four-unit provisional restorations were tested. Loss of marginal cement seal was monitored using strain gauges located occlusogingivally at the distal of the second molar abutment and the mesial of the first premolar abutment of a four-unit posterior fixed provisional restoration with two pontics. The provisional restorations were then placed in an Instron testing machine and loaded to initial fracture. Stiffness was calculated from the Instron recordings. The provisional designs were permachrome band-reinforced, wire-reinforced, and a nonreinforced control. Analysis showed: (1) the band-reinforced design withstood a significantly greater load before loss of cement seal (P< or =.05); (2) the band-reinforced design had a significantly higher stiffness (P< or =.05); and (3) there was no difference between the three designs for load at initial fracture. Within the same sample it was found that for both band- and wire-reinforced designs the premolar abutment lost the marginal cement seal at a significantly lower load than the molar (P< or =.05). For the control there was no significant difference for load at marginal cement seal loss between abutments.

Acrylic Resins↗
PubMed1996

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.

Amygdala↗
PubMed1996

A comparative study of fracture resistance between morphologic dowel and cores and a resin-reinforced dowel system in the intraradicular restoration of structurally compromised roots.

The intraradicular reinforcement of structurally compromised roots has been advocated for endodontically treated teeth with thin remaining walls. The purpose of this in vitro study was to investigate the validity of intraradicular reinforcement. After the crowns were removed, forty structurally weakened central incisors were divided into two main groups for morphologic dowel rehabilitation or resin reinforcement and dowel rehabilitation. Within both these groupings, half the specimens were ferruled to assess the effects of a ferrule on fracture resistance. All dowels were cemented with resin cements. The resistance to a simulated masticatory load of a resin-reinforced post and core system was significantly greater than that of a morphologic post and core procedure. When a bonded resin reinforcement and dowel cementation was used on structurally weakened roots, there was no statistically significant difference between post and core restorations that used a ferrule and those without a ferrule.

Analysis of Variance↗
PubMed1998

Serotonin1B receptor stimulation enhances cocaine reinforcement.

The effects of serotonin1B [5-hydroxytryptamine1B (5-HT1B)] receptor activation on cocaine reinforcement were investigated using intravenous cocaine self-administration by rats. The 5-HT1B receptor agonists 5-methoxy-3-1,2,3,6-tetrahydro-4-pyridinyl-1H-indole (RU 24969) (0.3-3 mg/kg), 3-(1,2,5, 6-tetrahydro-4-pyridyl)-5-propoxypyrrolo[3,2-b]pyridine (CP 94,253) (0.3-3 mg/kg), and 3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrolo[3, 2-b]pyridine (CP 93,129) (3 and 10 micrograms, i.c.v.) each dose-dependently reduced the self-administration of a cocaine dose on the descending limb of the fixed-ratio 5 (FR-5) cocaine dose-effect function, in a manner similar to the effect produced by increasing the unit dose of cocaine. In addition, each of these 5-HT1B agonists lowered the threshold dose of cocaine that supported self-administration. These results are consistent with a 5-HT1B agonist-induced potentiation of cocaine reinforcement. On a progressive ratio schedule of reinforcement, RU 24969 and CP 94,253 dose-dependently (0.3-3 mg/kg) increased the highest completed ratio for cocaine self-administration, again by producing behavioral alterations similar to those induced by increasing the unit dose of cocaine. The effect of CP 94,253 was dose-dependently blocked by the 5-HT1B/1D receptor partial agonist 2'-methyl-4'-(5-methyl[1,2, 4]oxadiazol-3-yl)-biphenyl-4-carboxylic acid[4-methodoxy-3-(4-methyl-piperazin-1-yl)-phenyl]-amide (GR 127, 935) (0.3-10 mg/kg) but was unaffected by the 5-HT1A receptor antagonist 4-iodo-N-[2-[4-(methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinyl- benzamide (p-MPPI; 1-10 mg/kg). Self-administration behavior was not maintained when either RU 24969 or CP 94,253 was substituted for cocaine, indicating that these 5-HT1B agonists do not produce significant reinforcing effects alone. Together, these findings indicate that 5-HT1B receptor stimulation facilitates the reinforcing properties of cocaine. These results are in opposition to recent findings with 5-HT1B receptor knock-out mice and may have important ontogenic implications in the area of drug abuse research.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1975

Influence of delta9-tetrahydrocannabinol on partial reinforcement effects.

Two experiments were performed with rats trained with either continuous reinforcement (food) or random 50% partial reinforcement for running in a straight alley. Half the rat were trained with daily injections of 0.5 mg/kg delta9-tetrahydrocannabinol (THC) and half with vehicle injections, all animals being extinguished with vehicle injections in Expt. 1 and with THC injections in Expt. 2. The partial reinforcement acquistion effect was abolished by THC during training; the partial reinforcement extinction effect was abolished by THC either during training of during extinction. In these respects THC resembles amylobarbitone and alcohol.

Animals↗
PubMed1992

Reinforcing effects of enantiomers of N,N-dimethylamphetamine in squirrel monkeys.

Reinforcing effects of the (+)- and (-)-enantiomers of N,N-dimethylamphetamine, a drug that is abused in humans, were studied in squirrel monkeys (Siamiri sciureus) trained under schedules of intermittent cocaine reinforcement. During training, each 30th response produced an injection of cocaine (fixed-ratio schedule), which was followed by a 1-min period during which lights were out and responses had no scheduled consequences (timeout). Sessions in which cocaine injections were scheduled alternated in an irregular sequence with sessions in which saline injections were scheduled. After training, response rates were well maintained by cocaine (response rates approximated 1.4 responses per second) but occurred relatively infrequently during sessions in which saline was injected (response rates approximated 0.3 responses per second). Doses of 10 to 56 micrograms/kg/injection of (+)-N,N-dimethylamphetamine maintained rates of responding significantly higher than those maintained by saline. The (-)-enantiomer did not maintain rates of responding that were higher than those maintained by saline when tested at doses up to 100 micrograms/kg/injection. These findings support previous results indicating that N,N-dimethylamphetamine will function as a reinforcer in laboratory animals. Further, they suggest that the significant reinforcing activity of this drug is restricted to the (+)-enantiomer.

Animals↗
PubMedDate not supplied

Interactions between atropine, chlorpromazine and cocaine on food reinforced behavior.

Previous investigations have demonstrated the ability of atropine and chlorpromazine pretreatment to increase intravenous cocaine self-administration in rhesus monkeys. These results were interpreted as resulting from either an antagonism of cocaine's reinforcing effect or an effect of cocaine which may interfere with its self-administration. The generality of the postulated drug antagonism was tested in monkeys exhibiting stable FR10 food-reinforced behavior. Intramuscular pretreatment with 0.25-4.0 mg/kg of chlorpromazine significantly depressed this behavior as did pretreatment with 0.25-2.0 mg/kg of atropine. These same dosages had been shown to increase cocaine self-administration. Fifteen-minute influsions of cocaine (1.0-10 mg/kg), which began 15 min after session onset, also resulted in a depression of food reinforced behavior. When chlorpromazine pretreatment and cocaine infusion were combined, the decrement in food reinforced responding was lessened. However, when cocaine infusion and atropine pretreatment occurred concurrently, the depression in responding was increased. These data indicate that chlorpromazine may nonspecifically antagonize the behavioral effects of cocaine; whereas, atropine may enhance these effects.

Animals↗
PubMed1991

Orally delivered cocaine functions as a positive reinforcer in C57BL/6J mice.

Cocaine serves as a reinforcer across several routes of administration and species. However, whether orally delivered cocaine serves as a positive reinforcer has not been systematically established. We determined the extent to which contingent access to orally delivered cocaine would maintain lever pressing behavior in C57BL/6J mice who had a prior history of operant ethanol-reinforced behavior. The findings presented in this report demonstrate that orally delivered cocaine can serve as a reinforcer of operant behavior. A drug substitution procedure where cocaine was substituted for gradually decreasing ethanol concentrations was successful in inducing pharmacologically significant intakes of cocaine under a fixed ratio (FR) schedule of drug access. When ethanol was removed, responding for cocaine continued. As FR size was increased, proportionate increases in responding occurred except at the highest FR value. Responding maintained by cocaine significantly exceeded responding maintained by vehicle, with the mice typically consuming 6-10 mg/kg cocaine per 30-min session. The utilization of inbred strains and the procedures followed in the present studies should prove useful in determining the extent of both genetic and environmental influences on various behavioral effects of cocaine and their mechanisms of action.

Administration, Oral↗
PubMed1992

Etonitazene delivered orally serves as a reinforcer for Lewis but not Fischer 344 rats.

Oral etonitazene self-administration was systematically investigated in two inbred strains of rats, Lewis (LEW) and Fischer 344 (F344). For LEW rats, etonitazene maintained higher rates of lever pressing and was consumed in larger volumes than the water vehicle when the reinforcement schedule was fixed ratio (FR) 8. In contrast, with F344 rats responding did not systematically exceed water values at any etonitazene concentration. LEW rats also drank substantially more etonitazene than F344 rats, and at FR 8 only LEW rats showed the typical inverted U-shaped function between etonitazene concentration and number of responses. For the LEW strain, response rate increased as FR size increased from FR 1 to FR 2 and FR 4, but decreased at FR 8. For the F344 strain, as FR size increased response rate showed small increases, but the response rates were far lower than those of the LEW strain. The results support the conclusion that etonitazene was an effective reinforcer for LEW but not F344 rats. These findings demonstrate genetic differences in opioid reinforcement of operant behavior and indicate that genotype can be an important determinant of whether etonitazene serves as a reinforcer.

Administration, Oral↗
PubMed1994

Differential sensitivity of operant behaviors to changes in the concentration of a sucrose reinforcer: effects of pimozide.

The sensitivity of operant response rates to changes in a sucrose reinforcer was examined in well-trained animals maintained on a variable ratio (VR) or variable interval (VI) schedule (experiment 1). Although VR performance showed greater resistance to small reductions in the concentration of the sucrose reinforcer than VI performance, VR performance was more sensitive to large reductions in the sucrose concentration. Despite this differential sensitivity only the smallest dose of pimozide (0.125 mg/kg) differentially affected these behaviors by reducing VI rates without affecting VR rates. These and other results support the view that low doses of pimozide reduce the hedonic impact of the reinforcer. The results also indicate that the attenuation of operant responding by higher doses (0.25, 0.5, and 1.0 mg/kg) cannot be solely a result of the blunting of reward. Experiment 2 demonstrated that when rats drink in daily, brief one-bottle tests they show greater resistance to reductions in the sucrose concentration than when they lever-press for sucrose, and require a higher dose of pimozide (2.0 mg/kg) to attenuate consumption. Together the results of both experiments suggest that the greater the resistance to reductions in the reinforcement value, the greater the dose of pimozide necessary to attenuate performance. We discuss the importance of attaining a more complete understanding of the factors in control of operant performance in order to better assess the effects of neuroleptics on reward.

Animals↗
PubMed1986

Corticosterone, free fatty acid and glucose responses of rats to footshock, fear, novel stimuli and instrumental reinforcement.

Rats were subjected to sessions of footshock, fear stimuli and instrumental reinforcement to assess responses of blood corticosterone, free fatty acids (FFA) and glucose. The corticosterone response to fearful situations exhibited a stimulus generalization decrement, thus demonstrating a contribution of Pavlovian classical conditioning to the activity of the hypothalamo-pituitary-adrenal system. Corticosterone levels were shown to decrease during operant sessions with large water reinforcements, while FFA and glucose levels were increasing, thus dissociating these stress measures. FFA responses to intermittent, intense footshock were found to be quadratic; blood levels of FFA increased within 10 min, decreased by 40 min, and then showed the increase with 80-min long sessions previously reported in the literature. This pattern of response was not influenced by prior food deprivation or different methods of sampling blood. Blood levels of FFA increased generally to novel/fearful situations and instrumental reinforcement sessions, which were stimulus situations less stressful than the footshock sessions. Glucose increases occurred to footshock and instrumental reinforcement sessions under some conditions, depending more than corticosterone and FFA on prior food deprivation and blood sampling method.

Animals↗
PubMed1999

Reinforcement enhances hippocampal acetylcholine release in rats: an in vivo microdialysis study.

Rats were trained to press a lever under a 'Multiple FI-60s and Extinction' schedule with food reinforcements. After learning the task, an in vivo microdialysis probe was inserted into the dentate gyrus and CA3 regions of the hippocampus, and the sequential changes in the dialysate acetylcholine (ACh) concentration were analyzed. In the session, two fixed-interval of reinforcement (FI) components (for 20 min) and two extinction (EXT) components (for 30 min) were alternated to examine the correlation between behavioral and neurochemical outcomes. The dialysate ACh concentration increased during the FI component and returned to the baseline during the EXT component of the schedule. Next, in order to dissociate the effect of discrimination from the effect of rewarding on the neurochemical changes in the hippocampus, we used a final TEST period (for 20 min) during which the actual schedule was extinction but the discriminative stimulus was on, i.e. the manifest condition of the test period was reinforcement. In the TEST period, the animals pressed the lever with almost the same frequency as during the FI component; however, the dialysate ACh concentration did not increase above the baseline concentration. These results suggest that ACh release in the rat hippocampus is associated with reinforcement but not with discrimination in operant conditioning.

Acetylcholine↗
PubMed2002

Marijuana effects on sensitivity to reinforcement in humans.

Under controlled laboratory conditions, eight adult subjects smoked placebo and three different potencies of marijuana cigarettes ranging in Delta(9) THC content. Immediately following smoking, subjects were exposed to a laboratory task that provided concurrently available response options. One option systematically decreased in reinforcement frequency throughout the session, and thus required a reallocation of behavior to the non-decreasing option to maximize monetary earnings. After smoking the two highest doses (1.77% and 3.58% Delta(9) THC) subjects earned fewer reinforcers and allocated a higher proportion of responding to the decreasing option, compared with placebo and the lowest dose. The difference in reinforcers earned could not be accounted for by a change in response rates. Quantitative and graphical analyses revealed that the higher doses produced considerable periods of time spent on the decreasing option despite earning few reinforcers. The data are discussed with regard to marijuana effects on dopamine/cannabinoid systems and adaptive behavior change.

Adult↗