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See detailEffects of the social conditions of housing through testing on cocaine-induced contextual sensitisation and conditioned locomotion in C57BL/6J mice
Michel, Alexa ULg; Tirelli, Ezio ULg

in Progress in Neuro-Psychopharmacology & Biological Psychiatry (2002), 26(6), 1185-1191

The potential differential effects of isolated and collective housing through the testing phase on sensitisation to cocaine-induced locomotion, the subsequent conditioned locomotion and the context ... [more ▼]

The potential differential effects of isolated and collective housing through the testing phase on sensitisation to cocaine-induced locomotion, the subsequent conditioned locomotion and the context-dependent expression of sensitisation were examined in C57BL/6J male mice. [less ▲]

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See detailPost-sensitisation conditioned hyperlocomotion induced by cocaine is augmented as a function of dose in C57BL/6J mice
Michel, Alexa ULg; Tirelli, Ezio ULg

in Behavioural Brain Research (2002), 132(2), 179-186

The study tested the possibility of a positive relationship between the dose of cocaine and the size of the placebo effect generated after contextual sensitisation to the behavioural effects of cocaine ... [more ▼]

The study tested the possibility of a positive relationship between the dose of cocaine and the size of the placebo effect generated after contextual sensitisation to the behavioural effects of cocaine. Male C57BL/6J mice were first injected (subcutaneous, s.c.) over seven successive daily sessions with saline or one of three doses of cocaine (2.5, 5 or 7.5 mg/kg), either in the test room or in the colony room (before being placed in a novel cage tub). On the test day, 24 h after chronic pre-treatment, mice from the four conditions were challenged under saline in the test room. Mice were video-recorded and their behaviours were scored using a time-sampling technique. A dose-dependent development of sensitisation was first generated. On the saline challenge test day, significant levels of placebo hyperlocomotion were obtained for mice previously given 5 and 7.5 mg/kg, but not 2.5 mg/kg cocaine, the effect being significantly greater in the mice pretreated with the highest dose than in those receiving the intermediate one, which exhibited a placebo effect that was greater than that of the mice pretreated with 2.5 mg/kg cocaine. Therefore, the magnitude of the placebo effect was a function of the intensity of the unconditioned stimulus (the dose used to generate sensitisation). Such results directly support the Pavlovian conditioning account of post-sensitisation placebo effects. [less ▲]

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See detailConditioned hyperkinesia induced by cocaine in mice is dose-dependent but not correlated with the unconditioned response or the contextually-sensitized response
Michel, Alexa ULg; Tirelli, Ezio ULg

in Behavioural Pharmacology (2002), 13(1), 59-71

The aims of the study were to test whether drug dose is positively related to the magnitude of the conditioned response following sensitization to the behavioural effects of cocaine and to investigate the ... [more ▼]

The aims of the study were to test whether drug dose is positively related to the magnitude of the conditioned response following sensitization to the behavioural effects of cocaine and to investigate the relationship between the conditioned response and cocaine-induced sensitization. Male mice (C57BL/6J) were first injected over seven successive days with either saline or cocaine at 2.5, 5, 10 or 20 mg/kg s.c., in the testing room. On the test day, 24 h after the last injection, mice from all conditions were challenged with saline in the testing room to test for conditioned cocaine effects. Mice were video-recorded and various behaviours were later scored using a time-sampling technique. Cocaine-elicited orofacial stereotypy was significantly sensitized at the two highest doses and dose-dependently conditioned at the three highest doses. Cocaine-increased locomotion was sensitized at the three highest doses and significantly conditioned at 10 and 20 mg/kg. Cocaine-increased sniffing did not change over pretreatment at any dose, and was conditioned only at 10 mg/kg. Cocaine-decreased immobility also did not change over pretreatment at any dose, but was conditioned at 10 and 20 mg/kg. Concomitantly, rearing was reduced by cocaine at 10 and 20 mg/kg, without sensitization being induced, and it was reduced under saline challenge after 5 mg/kg cocaine, while cocaine-decreased grooming was sensitized at the three highest doses and conditioned at 10 and 20 mg/kg cocaine. There was a positive relation between the size of the conditioned response for orofacial stereotypy and the magnitude of the unconditioned stimulus (the doses), a result conforming to the Pavlovian account of the placebo effect. This could also be concluded from considering the behaviour patterns as components of a unique placebo effect (hyperkinetic syndrome), since orofacial stereotypy, very apparent at 20 mg/kg cocaine, interfered at that dose with the full-blown expression of locomotion and sniffing, both yielding (approximately) inverted U-shaped dose-effect curves. However, no correlation was found between the magnitude of the conditioned response and the amplitude of sensitization (the difference between the initial unconditioned non-sensitized response and the last unconditioned sensitized response), a finding which indicates that conditioned responding does not participate in the generation of the sensitized effects, contrary to the 'excitatory conditioning model of contextual sensitization' [less ▲]

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See detailDay-by-day maturation of the long-term expression of cocaine sensitization acquired before weaning in the rat
Tirelli, Ezio ULg

in Behavioral Neuroscience (2001), 115(5), 1101-1110

This study aimed to identify the ontogenetic period during which long-term expression of behavioral sensitization to cocaine begins to emerge. Rat pups aged 4, 8, 12, or 16 days received a pretreatment of ... [more ▼]

This study aimed to identify the ontogenetic period during which long-term expression of behavioral sensitization to cocaine begins to emerge. Rat pups aged 4, 8, 12, or 16 days received a pretreatment of 4 daily injections of 15 mg/kg sc cocaine paired with the test chamber for 45 min. Pups were then tested for sensitization in that context after abstinence intervals ranging from 2 to 10 days. On test days, pups were videotaped, and their behavior was scored later. Sensitization was detected after intervals of 2, 4, 5, or 9 days in pups aged 4-7, 8-11, 12-15, or 16-19 days during pretreatment, respectively. These results suggest that the mechanisms for long-term retention of sensitization mature incrementally in the rat, starting to emerge gradually after the I st week of age, whereas those relevant to short-term retention and initiation of sensitization are present earlier. [less ▲]

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See detailShort-term contextual sensitisation and conditioned hyperkinesia produced by cocaine in suckling rats aged 4-10 days and 14-20 days
Tirelli, Ezio ULg

in Psychopharmacology (2001), 156(1), 46-52

RATIONALE: It was hypothesised that the failure to generate sensitisation to the behavioural effects of a motor stimulant in suckling rats was mainly due to not pairing the drug with the test context ... [more ▼]

RATIONALE: It was hypothesised that the failure to generate sensitisation to the behavioural effects of a motor stimulant in suckling rats was mainly due to not pairing the drug with the test context during chronic pretreatment. OBJECTIVE: This study probed the capabilities of neonatal and infant rat pups to show short-term context-specific sensitisation and conditioned drug activity produced by cocaine. METHODS: Two similar experiments were conducted on rat pups aged 4-10 days or 14-20 days, each experiment comprising three phases: a sensitisation phase (days 4-8 and days 14-18 of age), a test session under cocaine for context specificity of sensitisation (day 9 and day 19 of age) and a test session under saline for conditioned drug effects (day 10 and day 20 of age). Over five daily sessions, pups first received an injection of either 16 mg/kg cocaine (paired group) or saline (unpaired group) in test chambers, and 110 min later the converse injections in the vivarium (in a cage that was different from the home cage). A third group received saline in both contexts. Behaviour was scored using videotapes. RESULTS: Sensitisation developed in the paired groups at both ages. In 4- to 10-day-old pups, sensitisation was expressed via locomotion (matrix crosses) and also horizontal and vertical activities (categories comprising several age-specific movements). In 14- to 18-day-old pups, it was displayed by increases in head movements and vertical activity, and by a decline in stationary position. These effects were confirmed to be context specific on the test sessions (day 9 or day 19), the paired groups producing by far the greatest values. On the conditioning test, the paired groups also produced the greatest amounts of the above-mentioned behaviours, revealing a conditioned drug effect. Additionally, the conditioned effect scores were higher than those of two additional groups that had been treated similarly to the others but outside the chamber until the two tests (controlling for a withdrawal effect and possible novelty-induced activity in the test context). There were no differences between these unexposed groups, indicating that no abstinence effect occurred. CONCLUSIONS: The results demonstrate that neonatal rats are capable of showing physiological/non-contextual cocaine-induced behavioural sensitisation as well as its context-specific expression and the conditioned activity following its establishment. [less ▲]

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See detailDose-dependent caffeine-induced conditioned locomotion in mice
Pirona, Alexandre; Ferrara, André Onofrio; Tirelli, Ezio ULg

in Behavioural Pharmacology (2001), 12

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See detailA behavioural analysis of the conditioned drug effects and the context-specific sensitization produced by a low and a high dose of cocaine
Michel, Anne; Tirelli, Ezio ULg

in International Journal of Neuropsychopharmacology (2000), 3(Supplement), 130

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See detailExpectations can influence not only the psychomotor but also the some of the cognitive effects of caffeine
Bernaerts, Pascale; Servais, Christine; Tirelli, Ezio ULg

in International Journal of Neuropsychopharmacology (2000), 3(Supplement), 113

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See detailSelective effects of nicotine on attentional processes
Mancuso, G.; Warburton, D. M.; Melen, Marie-Rose ULg et al

in Psychopharmacology (1999), 146(2), 199-204

RATIONALE: It is now well established from electrophysiological and behavioural evidence that nicotine has effects on information processing. The results are usually explained either by a primary effect ... [more ▼]

RATIONALE: It is now well established from electrophysiological and behavioural evidence that nicotine has effects on information processing. The results are usually explained either by a primary effect of nicotine or by a reversal effect of a nicotine-induced, abstinence deficit. In addition, there is dispute about the cognitive processes underlying the changes in performance. METHODS: This study has approached the first question by using the nicotine patch, in order to administer nicotine chronically. In addition, we examined the effects of nicotine on attention with a selection of tests which assessed the intensity and selectivity features of attention, using the Random Letter Generation test, the Flexibility of Attention test and the Stroop test. RESULTS: Nicotine enhanced the speed of number generation and the speed of processing in both the control and interference conditions of the Stroop test. There were no effects on attentional switching of the Flexibility of Attention test. CONCLUSION: The results are consistent with the hypothesis that nicotine mainly improves the intensity feature of attention, rather than the selectivity feature. [less ▲]

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See detailAnticipatory responding, exclusive drug-context pairing and conditioned effects in sensitization to apomorphine-induced climbing in mice
Tirelli, Ezio ULg; Heidbreder, C.

in Progress in Neuro-Psychopharmacology & Biological Psychiatry (1999), 23(3), 505-518

1. The conditioning aspects of contextual sensitization were examined in the case of apomorphine-induced wall-climbing in mice, measuring onset latencies of the pharmacological response and controlling ... [more ▼]

1. The conditioning aspects of contextual sensitization were examined in the case of apomorphine-induced wall-climbing in mice, measuring onset latencies of the pharmacological response and controlling differential habituation to the test context during drug treatment. 2. Sensitization was generated in male out-bred mice which received intermittent i.p. injections of 0.4 mg/kg apomorphine over 9 daily sessions. On day 10, they were tested for contextual sensitization (all mice under apomorphine). On day 14, after 3 sessions of reinstatement, mice were tested for conditioned climbing (all mice under saline). 3. It was found that simultaneous exposure to both apomorphine and the test context facilitated the expression of a full-blown contextual sensitization (some non-contextual sensitization emerging too); importantly, sensitization was accompanied by a progressive shortening of the latencies to climb (before injections); conditioned climbing appeared only in mice pairing the drug with the test context, that response being absent in mice treated outside the context or never exposed to the context. 4. It is likely that contextual sensitization to apomorphine-induced climbing relies on Pavlovian conditioning processes rather than on habituation-related processes. [less ▲]

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See detailConditioning of and contextual sensitization to apomorphine-induced climbing in mice : evidence against the habitation hypothesis
Tirelli, Ezio ULg; Heidbreder, C.

in Behavioral Neuroscience (1999), 113(2), 368-376

Several predictions of the habituation hypothesis of conditioned drug effects were tested by looking at contextual sensitization to apomorphine-induced climbing in mice (Mus musculus). Mice were first ... [more ▼]

Several predictions of the habituation hypothesis of conditioned drug effects were tested by looking at contextual sensitization to apomorphine-induced climbing in mice (Mus musculus). Mice were first sensitized to that effect after 9 daily injections of 0.4 mg/kg apomorphine in the test context. Other mice received the same treatment outside the test context. On Day 10, all mice were challenged with either saline (conditioned drug effects test) or apomorphine (contextual sensitization test). On both tests, the levels of climbing of mice that received apomorphine paired with the test context during the intermittent treatment were significantly higher than those of mice that were experiencing the test context for the first time (unexposed mice). Also, the rate of extinction in conditioned mice did not parallel the rate of habituation in the unexposed mice. Results contradict the habituation hypothesis of conditioned drug effects and contextual sensitization. ((c) 1999 APA/PsycINFO, all rights reserved)(journal abstract) [less ▲]

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See detailEffects on nicotine administered via a transdermal delivery system on vigilance : a repeated measure study
Mancuso, Giovanna; Andrès Bénito, Pilar; Ansseau, Marc ULg et al

in Psychopharmacology (1999), 142(1), 18-23

Tested 15 male smokers (aged 18-25 yrs) in a within-Ss design to determine the influence of a transdermal patch of 21 mg nicotine on vigilance. Ss were tested on the Rapid Visual Information Processing ... [more ▼]

Tested 15 male smokers (aged 18-25 yrs) in a within-Ss design to determine the influence of a transdermal patch of 21 mg nicotine on vigilance. Ss were tested on the Rapid Visual Information Processing test 1.3, 3 and 6.3 hrs after patch application, to verify the involvement of the dose of nicotine on the performance. The results confirm and extend the knowledge on the increasing effects of nicotine on vigilance previously found with orally and transdermally administered nicotine. Moreover, results show that such performance was independent of the time of nicotine absorption, which suggests that a relatively low dose of nicotine suffices to activate vigilance processing. Regarding motor performance, no convincing effect of nicotine was observed on reaction time. ((c) 1999 APA/PsycINFO, all rights reserved) [less ▲]

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See detailConditioned apomorphine-induced climbing: Influence of cue-exposure and the contribution of "forgetting" to the effects observed
Tirelli, Ezio ULg; Heidbreder, Christian; Terry, Phil

in Behavioural Pharmacology (1999), 10

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See detailLes facteurs biologiques en psychologie
Tirelli, Ezio ULg

in Rondal, Jacques (Ed.) Introduction à la psychologie scientifique (1999)

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See detailContexual sensitization to the behavioral effects of cocaine in neonatal rats
Tirelli, Ezio ULg

in Developmental Psychobiology (1999), 25

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See detailAmphetamine-Induced Conditioned Activity and Sensitization: The Role of Habituation to the Test Context and the Involvement of Pavlovian Processes
Tirelli, Ezio ULg; Terry, P.

in Behavioural Pharmacology (1998, September), 9(5-6), 409

Behaviours associated with drug action can sometimes be elicited, in the absence of drug, by exposure to stimuli that were present during drug administration. Such a finding is usually interpreted as a ... [more ▼]

Behaviours associated with drug action can sometimes be elicited, in the absence of drug, by exposure to stimuli that were present during drug administration. Such a finding is usually interpreted as a conditioned drug effect. Often, however, the outcome could arise if drug administration in a particular environment retarded behavioural habituation to that environment. To test the 'habituation hypothesis' of conditioned drug effects, mice received 10 daily injections of d-amphetamine ('paired' group) or saline ('unpaired') in test boxes, and the converse injections in the colony room. Another group received saline in both environments. The apparatus and procedures yielded minimal habituation of behaviours (ambulation and rearing) over sessions. Only the paired group demonstrated behavioural sensitization, indicating environment-specific sensitization. The paired group also showed more ambulation and rearing than the others on the critical test of conditioning (saline injection in test box); moreover, their conditioning test scores were higher than those of the other groups on their first exposure to the test boxes, contradicting the habituation hypothesis. Further supporting the involvement of Pavlovian conditioning, levels of ambulation and rearing measured for 10 min before each injection increased in the paired group, relative to the unpaired groups, over successive pairing sessions. Tests controlling for differential handling/injection experience produced results consistent with those previously obtained. Together, the findings are incompatible with the habituation hypothesis, and further support the role of Pavlovian conditioning. [less ▲]

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See detailEvidence for behavioral sensitization to cocaine in preweanling rat pups
Wood, R. D.; Tirelli, Ezio ULg; Snyder, K. J. et al

in Psychopharmacologia (1998), 138(2), 114-123

Sought to determine whether promoting context-dependent sensitization might facilitate expression of sensitization in preweanlings. Sprague-Dawley rats were injected daily from postnatal day 14 to ... [more ▼]

Sought to determine whether promoting context-dependent sensitization might facilitate expression of sensitization in preweanlings. Sprague-Dawley rats were injected daily from postnatal day 14 to postnatal day 20 with 0, 5, 15, or 30 mg/kg cocaine hydrochloride and placed for 30 min in either the experimental chamber or home cage. On postnatal day 21 (test day), Ss were challenged with either 15 mg/kg cocaine or saline prior to placement in the experimental chamber. Significant sensitization of cocaine-induced stereotyped head movements was evident in animals given 15 or 30 mg/kg chronically in the experimental chamber, but not when these same doses were given in the home cage. Less consistent evidence for cocaine-induced sensitization was seen when examining locomotion, although trends for sensitization of this behavior were seen in animals chronically injected in either the test chamber or home cage. Thus, preweanlings can exhibit cocaine sensitization, particularly in terms of stereotypy, when tested shortly after the chronic exposure period, with expression of this sensitization being facilitated by pairing the chronic injections with the test context. ((c) 1998 APA/PsycINFO, all rights reserved) [less ▲]

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