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PubMed1996

Classically conditioned motor effects do not occur with cocaine in an unbiased conditioned place preferences procedure.

Classical conditioning and behavioural sensitisation of motor activity induced with cocaine (10mg/kg, i.p.) were examined using an unbiased two-compartment conditioned place preference (CPP) procedure. Habituation of the rats to the testing environment prior to training was varied (i.e. either the rats were habituated to the environment for three 30min sessions or they were not) in order to examine a possible influence of latent inhibition on conditioned locomotion or behavioural sensitisation. Furthermore, rats were either trained with an explicit CS+ (cocaine-paired compartment) and CS- (vehicle-paired compartment), or else they were trained with no barrier between the compartments (effectively a single-compartment procedure with no explicit CS-) in order to examine a possible influence of stimulus change (training rats while confined to one compartment, but testing with no barrier between compartments). On a drug-free test day with free access to both compartments, rats previously exposed to cocaine in one compartment (CS+) and vehicle in the second compartment (CS-) spent more time in the CS+ compartment (conditioned place preference). However, under no circumstance was the rate of motor activity higher in the CS+ compartment than in the CS- compartment, as would be expected if cocaine-induced motor activity was classically conditioned to contextual cues. Whether or not increased activity extinguished with repeated drug-free exposures to previously drug-paired contexts depended on habituation experience. In addition, both habituation and current access to compartments (free or restricted) determined the presence of post-extinction sensitisation to a challenge dose of cocaine (7.5mg/kg). Classical conditioning and non-associative sensitisation, independently or together, cannot account for this pattern of results.

Journal Article↗
PubMed2003

Glucose metabolism in Lactococcus lactis MG1363 under different aeration conditions: requirement of acetate to sustain growth under microaerobic conditions.

Lactococcus lactis subsp. lactis MG1363 was grown in batch cultures on a defined medium with glucose as the energy source under different aeration conditions, namely, anaerobic conditions, aerobic conditions, and microaerobic conditions with a dissolved oxygen tension of 5% (when saturation with air was used as the reference). The maximum specific growth rate was high (0.78 to 0.91 h(-1)) under all aeration conditions but decreased with increasing aeration, and more than 90% of the glucose was converted to lactate. However, a shift in by-product formation was observed. Increasing aeration resulted in acetate, CO(2), and acetoin replacing formate and ethanol as end products. Under microaerobic conditions, growth came to a gradual halt, although more than 60% of the glucose was still left. A decline in growth was not observed during microaerobic cultivation when acetate was added to the medium. We hypothesize that the decline in growth was due to a lack of acetyl coenzyme A (acetyl-CoA) needed for fatty acid synthesis since acetyl-CoA can be synthesized from acetate by means of acetate kinase and phosphotransacetylase activities.

Acetates↗
PubMed2002

Breed comparisons of Angus, Charolais, Hereford, Jersey, Limousin, Simmental, and South Devon for weight, weight adjusted for body condition score, height, and body condition score of cows.

Breed means and differences for weight (CW, n = 19,851), height (CH, n = 14,553), and condition scores (CS, n = 19,536) recorded in four seasons per year were evaluated for 881 cows ranging from 2 to 7 yr of age from Cycle I of the Germplasm Evaluation Program at the U.S. Meat Animal Research Center. Cows were straightbred Herefords and Angus and topcrosses from mating of Hereford, Angus, South Devon, Jersey, Simmental, Limousin, and Charolais sires to Hereford and Angus dams. The model included cow age, season of measurement, and their interactions, with year of birth, pregnancy-lactation (PL) code, and breed group as fixed effects for CW and CS. Analyses of weight adjusted for condition score included CS as covariate. Model for CH excluded PL. Random effects were additive genetic and permanent environmental effects. Data were analyzed by REML. Differences due to breeds of sire were significant for all traits. Differences were generally maintained across ages, with few interchanges in ranking through maturity. Rankings were in the following order: Jersey (lightest and shortest), Hereford-Angus (and reciprocal), Limousin, South Devon, Simmental, and Charolais (heaviest and tallest). The only exception was that Limousin-sired cows were heavier than South Devon-sired cows after 5 yr of age. Cows sired by breeds of British origin tended to be lighter than breeds of continental European origin. Adjustment for condition score changed estimates of breed differences. Rankings of breed groups, however, were generally the same for actual weight and weight adjusted for condition score. Results indicated that the part of the differences in weight due to differences in condition were of small magnitude. Differences tended to increase when adjusted for condition score, especially in contrasts of continental vs British breeds. Differences among breed groups for height followed differences for weight closely.

Age Factors↗
PubMed2004

Prevalence of musculoskeletal conditions, associated pain and disability and the barriers to managing these conditions in a rural, Australian Aboriginal community.

INTRODUCTION: Internationally, musculoskeletal conditions are a major morbidity issue for Indigenous populations and the social and economic burden imposed by musculoskeletal complaints is significant. However, little is known about the prevalence and associated pain and impairment of musculoskeletal conditions among rural Indigenous Australians. METHODS: The study was conducted between January 2001 and July 2002. DESIGN: A cross-sectional research design was used. SAMPLE: Participants included 189 Indigenous members of the community, 80 of whom were randomly selected and 109 were recruited using a convenience sample. The sample included 87 males (46%) and 102 females (53%). Participants' mean age was 44 years (+/-14.8). MEASURES: The main outcome measures were sites of current pain, self-reported levels of pain, limitations to activities of daily living, and barriers to managing these conditions. PROCEDURE: Following a screening survey participants underwent a clinical examination conducted by musculoskeletal health professional trained in standardised, clinical assessment procedures. RESULTS: Lower back pain, followed by neck, head and shoulder pain were the most common conditions. Approximately 57% of participants suffered from 2 to 4 musculoskeletal conditions. The most commonly endured level of pain was 'high'. There were no significant differences between male and female participants in terms of reported levels of pain. The level of pain reported was relatively high compared with the level of associated limitation of activities of daily living. A majority of participants had suffered from their principal condition for 7 weeks or more, indicating high levels of chronicity in the community. CONCLUSION: The majority of people living in this large rural, Indigenous community have learnt to live with chronic levels of pain affecting multiple anatomical sites. Strategies such as community musculoskeletal health promotion and appropriately trained community health workers can assist the community manage this chronic burden of disability. There is scope for further study into the musculoskeletal health of both rural and urban Indigenous populations.

Journal Article↗
PubMed1996

[Working conditions, living conditions and physical health problems declared among penitentiary administration personnel in France].

A cross-sectional epidemiological survey was conducted among prison staff in France to investigate the relationships between working conditions and health. The sample included men and women 20 to 64 years old belonging to all categories of prison personnel: prison guards, administrative staff, socioeducational workers, technicians, health care workers, and managers (n = 4587, response rate 45.7%). A mailed self-administered questionnaire was used to assess sociodemographic characteristics, working conditions, and physical and mental disorders. Multiple logistic regression analyses were conducted to determine the effects of working conditions and social relationships on health of prison staff. However, the results reported here only concern 17 health disorders: body mass index, sick leave, medication use, accidents, digestive disorders, lower extremities and back disorders, hypertension, hemorrhoids, arthritis, skin disorders, urinary infections, chronic bronchitis, cholesterol, gastric ulcer, respiratory infections, ocular disorders. The living non professional conditions mostly associated with health disorders were financial difficulties (OR: 1.9 for digestive disorders, 1.8 for gastric ulcer, 1.7 for medication use) and irregularity of meals (OR = 1.5 for digestive disorders, and hypertension). In the occupational environment, the factors most associated with health disorders are seniority (OR = 4.2 for arthritis, 2.3 for cholesterol) and constraints (OR = 1.7 for lower extremities disorders). In spite of some limits associated to this kind of study, relationships between occupational and non occupational factors and physical health conditions were observed; the results also pointed out the protective role of the social relationships for health conditions.

Administrative Personnel↗
PubMed2001

Comparison of single unit responses to tone, light, and compound conditioned stimuli during rabbit classical eyeblink conditioning.

Unit recordings and lesion studies have implicated the cerebellum as an essential site for the acquisition and maintenance of the conditioned eyeblink response. The current study looked at the neural characteristics of conditioned stimulus (CS) processing in the interpositus nucleus of the cerebellum after training New Zealand white rabbits (Oryctolagus cuniculus) in one of two conditioning paradigms: (a) compound conditioning (CMP), a compound CS consisting of light and tone paired with an air puff unconditioned stimulus (US); or (b) stimulus compounding (ALT), alternating blocks of tone CS and light CS trials paired with the air puff US. Single unit responses were recorded during five sessions after the animals had reached an asymptotic level of responding. Animals were tested for behavioral and neural responses to CS alone trials that included tone alone, light alone, and compound tone-light trials. For the CMP group, the compound CS elicited 80 to 90% conditioned eyeblink responses (CRs), whereas the individual tone and light CSs elicited only 40 to 50% CRs. For the ALT group, all three CSs (tone, light, and compound) elicited very high levels of responding of at least 80% CRs. For the CMP group, there were roughly equal numbers of cells responding to all of the CSs. This includes cells that responded exclusively to one, and only one, of the three stimuli and also those cells that responded to combinations of two or more. Cells from the ALT group were far more likely to respond exclusively to only one of the CSs. Both the behavioral and physiological results suggest that the compound tone-light stimulus was processed as a distinct stimulus, separate from the component tone and light. These results are discussed in the context of multisensory processing.

Acoustic Stimulation↗
PubMed1976

Conditioned suppression of an operant response using d-amphetamine as the conditioned stimulus.

The use of a drug state as a conditioned stimulus (CS) in a classical conditioning paradigm was investigated. Suppression of a single-lever food-reinforced response (variable-interval 60 s) served as an index of a classically conditioned response (conditioned suppression). d-Amphetamine (0.8 mg/kg) injections were paired with a series of inescapable shocks. Following drug-shock pairing, the effects of d-amphetamine on operant response totals was compared to effects obtained in control subjects which had received unpaired d-amphetamine and shock exposures. d-Amphetamine administered during daily operant sessions unaccompanied by shock was an effective CS for conditioned suppression of the operant response. Administration of cocaine hydrochloride (7.5 mg/kg) also produced a decrease in total responses, suggesting stimulus generalization from the shock-paired drug to a novel drug.

Animals↗
PubMed1992

Potentiation or diminution of discrete motor unconditioned responses (rabbit eyeblink) to an aversive pavlovian unconditioned stimulus by two associative processes: conditioned fear and a conditioned diminution of unconditioned stimulus processing.

In two experiments using the rabbit conditioned eyeblink preparation, the conditions under which a Pavlovian conditioned stimulus (CS) potentiates or diminishes the unconditioned response (UR) were examined. The results indicated that, after discrimination training (CS+ vs. CS-), the CS+ diminished UR amplitude at the training interstimulus interval (ISI). When CS+ trials were segregated into trials on which a conditioned response (CR) did or did not occur, the CS+ diminished the UR when it elicited a CR, but not when a CR failed to occur. When the CS-unconditioned stimulus (US) interval was lengthened to 10 s, the CS+ reliably potentiated the eyeblink UR on CR trials but did not potentiate responding on trials on which a CR was absent. The results are discussed in terms of the modulatory effects and temporal properties of conditioned fear and an associatively produced decrement in US processing.

Animals↗
PubMed1992

An auditory conditioned stimulus modulates unconditioned stimulus-elicited neuronal activity in the cerebellar anterior interpositus and dentate nuclei during nictitating membrane response conditioning in rabbits.

The effects of the presentation of an auditory conditioned stimulus (CS) on unconditioned stimulus (US)-elicited neuronal activity in the anterior interpositus (AIPN) and dentate (DN) nuclei of the cerebellum were investigated during the initial stages of classical conditioning of the nictitating membrane (NM) response in rabbits. In Experiment 1, a 500-ms CS (but not a 30-ms CS) facilitated US-elicited single-unit activity in the AIPN and depressed US-elicited activity in the DN during training. In Experiment 2, lesions of the AIPN but not of the DN prevented acquisition of conditioned NM responses. The results are interpreted within the framework of a model of classical conditioning that proposes that conditioned neuronal activity that underlies behavioral plasticity develops from the modulation of US-elicited neuronal activity by the CS.

Animals↗
PubMed1998

Classical eyeblink conditioning in two strains of mice: conditioned responses, sensitization, and spontaneous eyeblinks.

Conditioned eyeblink responses (CRs), sensitization, and spontaneous eyeblinks were studied in C57BL/6J and BALB/c mice. Both strains of mice acquired CRs during 10 days of classical delay eyeblink conditioning. The BALB/c mice reached a higher asymptotic CR level than the C57BL/6J mice. The CRs were extinguished and recovered in both strains following conditioned stimulus-alone and paired conditioned stimulus-unconditioned stimulus training. During 10 days of explicitly unpaired training, the control groups showed no signs of sensitization and low incidence of spontaneous eyeblinks. When switched to paired training, the unpaired groups exhibited significant conditioned inhibition. These results suggest that strain differences must be considered in experimental design and data interpretation for these basic aspects of associative learning and memory.

Analysis of Variance↗
PubMed1995

Conditioning of fear and conditioning of safety in rats.

In separate groups of rats forward and backward procedures for classical defensive conditioning were superimposed on on-going bar pressing for food. The forward conditioned stimulus elicited suppression of bar presses, indicating acquisition of fear. The backward stimulus paired with identical shock elicited behaviour typical for rats in a condition of safety and caused an increase of bar press rate. Enhancement of bar presses acquired in the course of backward conditioning was stable, immune to influences from unsignalled shocks presented in the same experimental context, and resistant to extinction when all shocks were discontinued. Properties of the employed variety of the backward conditioning procedure are discussed. When a brief shock overshadowed the onset of a backward stimulus, the remaining portion of the stimulus became a signal of safety.

Analysis of Variance↗
PubMed1975

Conditioned response-contingent delays of the unconditioned stimulus in human aversive conditioning.

Four groups of subjects were given either 0. 100, 500, or 1,000 msec delays of the unconditioned stimulus (UCS) contingent upon the occurrence of a conditioned response (CR) and were given a UCS 515 msec after conditioned stimulus (CS) onset when a CR did not occur. A fifth group received standard classical conditioning trials with an interstimulus interval of 515 msec. Overall performance decreased as CR-contingent UCS delay increased, with the classical conditioning group approximating the performance of the group receiving the 100-msec delay. The data were analyzed with the two-phase model of conditioning and the following results were obtained: The duration of Phase 1 of the model increased with contingent delay; operator limits associated with CR trials or with combined CR-CR (CR absent) trials decreased as a function of delay; and operator limits associated exclusively with CR trials were unaffected by the delay. Subjects receiving a contingent delay of 0 msec gave the shortest latency responses and exhibited reliable latency decreases across trials, suggesting an attempt to "beat" the UCS. The results were interpreted as contrary to what would be expected from low-of-effect theories which postulate that reinforcement results from a CR-UCS interaction, although they could be subsumed under a drive or an associative strength theory in which the aversive, or CR-supportive, strength of the UCS is assumed to be negatively correlated with contingent UCS delay.

Adult↗
PubMed2002

Classical conditioning in the rat fetus: involvement of mu and kappa opioid systems in the conditioned response.

When the Embryonic Day 20 (E20) rat fetus is given a conditioning trial involving a paired presentation of an artificial nipple (the conditioned stimulus; CS) with an intraoral infusion of milk (the unconditioned stimulus; US), it shows evidence of classical conditioning when again exposed to the CS during a test trial. Specifically, the fetus shows fewer oral grasp responses (the conditioned response; CR) when continuously presented with the artificial nipple. The present study further investigated this classically conditioned reduction in oral grasping. Separate experiments (a) examined the time course of the reduction in oral grasping (Experiment 1), (b) characterized the time course of mu opioid (Experiment 2) and kappa opioid (Experiment 3) involvement in the CR, and (c) described changes in fetal behavior (Experiment 4) associated with mu and kappa opioid effects on responding to the artificial nipple. The results are discussed in terms of opioid involvement in establishing and maintaining early suckling behavior.

Animals↗
PubMed2005

The hippocampus and appetitive Pavlovian conditioning: effects of excitotoxic hippocampal lesions on conditioned locomotor activity and autoshaping.

The hippocampus (HPC) is known to be critically involved in the formation of associations between contextual/spatial stimuli and behaviorally significant events, playing a pivotal role in learning and memory. However, increasing evidence indicates that the HPC is also essential for more basic motivational processes. The amygdala, by contrast, is important for learning about the motivational significance of discrete cues. This study investigated the effects of excitotoxic lesions of the rat HPC and the basolateral amygdala (BLA) on the acquisition of a number of appetitive behaviors known to be dependent on the formation of Pavlovian associations between a reward (food) and discrete stimuli or contexts: (1) conditioned/anticipatory locomotor activity to food delivered in a specific context and (2) autoshaping, where rats learn to show conditioned discriminated approach to a discrete visual CS+. While BLA lesions had minimal effects on conditioned locomotor activity, hippocampal lesions facilitated the development of both conditioned activity to food and autoshaping behavior, suggesting that hippocampal lesions may have increased the incentive motivational properties of food and associated conditioned stimuli, consistent with the hypothesis that the HPC is involved in inhibitory processes in appetitive conditioning.

Amygdala↗
PubMed1996

Alcohol-mediated tactile conditioned aversions in infant rats: devaluation of conditioning through alcohol-sucrose associations.

Three experiments were conducted to assess the plasticity of ethanol-mediated conditioned aversions to a tactile stimulus in infant rats. Ten- and 11-day-old rats first acquired an aversion to a texture, by virtue of its pairing with alcohol-induced intoxication. This first conditioning phase was followed by an associative devaluation procedure, a second phase in which sucrose was intraorally infused during alcohol-induced intoxication. Pups were then tested for their texture preference. Results indicated that infant rats readily express conditioned aversion to a tactile cue as a result of tactile-alcohol pairings and that this associative learning was not state dependent. When alcohol-texture conditioning was followed by sucrose-alcohol pairings, the magnitude of the texture aversion was dramatically reduced (Experiments 1 and 2). In Experiment 3 citric acid rather than sucrose was paired with alcohol intoxication following texture-alcohol pairings. The results indicated that this procedure strengthened texture conditioned aversions in terms of increased resistance to extinction. Taken as a whole these studies indicate that infants rapidly acquire alcohol-mediated texture aversions and that this memory is malleable and can be reduced or potentiated through manipulation of the representation of alcohol's unconditioned properties.

Animals↗
PubMed1989

Dose-dependent and baseline-dependent conditioning with d-amphetamine in the place conditioning paradigm.

The place conditioning paradigm was used to evaluate the positively reinforcing effects of d-amphetamine. During conditioning, female rats were injected (IP) with saline or one of five doses (0.625-5 mg/kg) of d-amphetamine (d-A) and confined to the initially non-preferred side of the testing apparatus. The highest dose of d-A failed to produce a significant preference. The four middle doses of the drug induced a similar preference. A significant increase from baseline was observed on the 4th post-conditioning test day in the five drug groups and controls when given an injection of 1.5 mg/kg d-A 15 min prior to placement in the chamber. Control and drug groups were separated into high and low initial preference sub-groups. Place preferences were more readily induced by d-A in the subgroups with initially high baseline preferences. These findings as well as those of others led us to conclude that the place conditioning paradigm is a somewhat problematic way of measuring drug reinforcement and that the effects observed may not solely be the result of the conditioning of the drug's reinforcing properties to a particular environment.

Animals↗
PubMedDate not supplied

Eyeblink conditioning in rats using pontine stimulation as a conditioned stimulus.

Previous studies using rabbits and ferrets found that electrical stimulation of the pontine nuclei or middle cerebellar peduncle could serve as a conditioned stimulus (CS) in eyeblink conditioning (Bao, Chen, & Thompson, 2000; Hesslow, Svensson, & Ivarsson, 1999; Steinmetz, 1990; Steinmetz, Lavond, & Thompson, 1985; 1989; Steinmetz et al., 1986; Tracy, Thompson, Krupa, & Thompson, 1998). The current study used electrical stimulation of the pontine nuclei as a CS to establish eyeblink conditioning in rats. The goals of this study were to develop a method for directly activating the CS pathway in rodents and to compare the neural circuitry underlying eyeblink conditioning in different mammalian species. Rats were given electrical stimulation through a bipolar electrode implanted in the pontine nuclei paired with a periorbital shock unconditioned stimulus (US). Paired training was followed by extinction training. A subset of rats was given a test session of paired training after receiving an infusion of muscimol into the anterior interpositus nucleus. Rats given paired presentations of the stimulation CS and US developed CRs rapidly and showed extinction. Muscimol infusion prior to the test session resulted in a reversible loss of the eyeblink CR. The results demonstrate that electrical stimulation of the pontine nuclei can be used as a CS in rodents and that the CS pathway is similar in rats, rabbits, and ferrets. In addition, the loss of CRs following muscimol inactivation shows that the conditioning produced with pontine stimulation depends on cerebellar mechanisms.

Animals↗
PubMed1997

Effects of the medium conditioned by endothelial cells under hypoxic condition on the phenotype of porcine pulmonary arterial smooth muscle cells.

The effects of the medium conditioned by endothelial cells under hypoxic condition on the phenotype modulation of pulmonary artery smooth muscle cells (PASMCs) were investigated by using cell culture and morphometrical analysis. The results showed that the number of diploid cells and alpha-sm-actin of PASMCs in the hypoxic endothelial cell conditioned medium group (HECCM) was lower and the myofibrilles were even less than that in normal endothelial cell conditioned medium group (NECCM). On the contrary, the volume density of rough endoplasmic reticulum (RER) and mitochondria of PASMCs in the HECCM group was higher than that in the NECCM group, i.e. altering from a contractile type to a synthetic type. However, under direct hypoxic condition for 24 h, the phenotype of cultured PASMCs remained unchanged, i.e. retained contractile type. It suggests that the HECCM can induce phenotype modulation of PASMCs, may be mediated by the pulmonary artery endothelial cells (PAECs) which can secrete some cytokins affecting the PASMCs.

Animals↗