References of "Michel, Alexa"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailCocaine-conditioned activity persists for a longer time than cocaine-sensitized activity in mice: Implications for the theories using Pavlovian excitatory conditioning to explain the context-specificity of sensitization
Tirelli, Ezio ULg; Michel, Alexa ULg; Brabant, Christian ULg

in Behavioural Brain Research (2005), 165(1), 18-25

The present study was aimed at testing the prediction of the Pavlovian excitatory conditioning explanation of context-specific sensitization that the sensitized effect (SE) should persist as long as the ... [more ▼]

The present study was aimed at testing the prediction of the Pavlovian excitatory conditioning explanation of context-specific sensitization that the sensitized effect (SE) should persist as long as the post-sensitization conditioned activity (CR). C57BL/6J mice were tested for the expression of cocaine-induced conditioned and sensitized locomotion on several intervals after the establishment of a sensitization in an unchanging context. A group of mice received 10 once-daily injections of 10 mg/kg cocaine (s.c.) in a short time prior to being tested in activity-meters for 60 min sessions (cocaine-pretreated group), mice from a control group receiving saline in the same manner (saline-pretreated group). On the test sessions, taking place 1, 8 and 28 days after cocaine pretreatment, half of the animals of each pretreatment group (n=8) received a challenge test with saline and the other half with 10 mg/kg cocaine in the pretreatment context room (for CR and SE tests, respectively). The CR was significantly expressed on the three successive saline-challenge tests, albeit the activity levels were markedly decreased on the 28-day retention test. In contrast, the SE was significantly expressed only during the first half of the 1-day test session and the first 10 min of the 8-day test session, no SE effect being expressed on the 28-day retention test. The results, suggesting a functional uncoupling of the CR from the SE, disprove the theories of context-specificity of sensitization based completely or partially on Pavlovian excitatory conditioning mechanisms. [less ▲]

Detailed reference viewed: 31 (3 ULg)
See detailValutazione del transessualismo primario e secondario tramite il Rorschach comprehensive system
Porcelli, P.; Affatati, V.; Michel, Alexa ULg et al

in Psicologia Medica e Psicoterapia (2004), 23

Detailed reference viewed: 9 (3 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 19 (2 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 17 (1 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 29 (4 ULg)
Peer Reviewed
See detailOntogenetic aspects of individual differences in behavioral responsiveness to cocaine in rats
Michel, Alexa ULg; Tirelli, Ezio ULg

in Behavioural Pharmacology (1996), 10(Suppl.), 211-212

Detailed reference viewed: 13 (0 ULg)