A rat model of operant negative reinforcement in opioid-dependent males and females

RATIONALE AND OBJECTIVE

Avoidance of opioid withdrawal plays a key role in human opioid addiction. Here, we present a procedure for studying operant negative reinforcement in rats that was inspired by primate procedures where opioid-dependent subjects lever-press to prevent naloxone infusions.

METHODS

In Experiment 1, we trained rats (n = 30, 15 females) to lever-press to escape and then avoid mild footshocks (0.13-0.27 mA) for 35 days (30 trials/d). Next, we catheterized them and implanted minipumps containing methadone (10 mg/kg/day) or saline. We then paired (4 times, single session) a light cue (20-s) with a naloxone infusion (20 µg/kg, i.v) that precipitated opioid withdrawal. Next, we trained the rats to escape naloxone injections for 10 days (30 trials/d). Each trial started with the onset of the opioid-withdrawal cue. After 20-s, the lever extended, and an infusion of naloxone (1 to 2.2 µg/kg/infusion) began; a lever-press during an 11-s window terminated the withdrawal-paired cue and the infusion. In Experiment 2, we trained rats (n = 34, 17 females) on the same procedure but decreased the footshock escape/avoidance training to 20 days.

RESULTS

All rats learned to lever-press to escape or avoid mild footshocks. In both experiments, a subset, 56% (10/18) and 33% (8/24) of methadone-dependent rats learned to lever-press to escape naloxone infusions.

CONCLUSIONS

We introduce an operant negative reinforcement procedure where a subset of opioid-dependent rats learned to lever-press to escape withdrawal-inducing naloxone infusions. The procedure can be used to study mechanisms of individual differences in opioid negative reinforcement-related behaviors in opioid-dependent rats.

Characterization of operant social interaction in rats: effects of access duration, effort, peer familiarity, housing conditions, and choice between social interaction vs. food or remifentanil

RATIONALE AND OBJECTIVE

Social factors play a critical role in drug addiction. We recently showed that rats will abstain from methamphetamine, cocaine, heroin, and remifentanil self-administration when given a choice between the addictive drug and operant social interaction. Here, we further characterized operant social interaction by determining the effects of access duration, effort, peer familiarity, and housing conditions. We also determined choice between social interaction vs. palatable food or remifentanil.

METHODS

We first trained single-housed male and female rats to lever-press for social interaction with a sex- and age-matched peer. Next, we determined effects of access duration (3.75 to 240 s), effort (increasing fixed-ratio schedule requirements or progressive ratio schedule), peer familiarity (familiar vs. unfamiliar), and housing conditions (single vs. paired housing) on social self-administration. We also determined choice between social interaction vs. palatable food pellets or intravenous remifentanil (0, 1, 10 µg/kg/infusion).

RESULTS

Increasing access duration to a peer decreased social self-administration under fixed ratio but not progressive ratio schedule; the rats showed similar preference for short vs. long access duration. Social self-administration under different fixed ratio requirements was higher in single-housed than in paired-housed rats and higher for a familiar vs. unfamiliar partner in single-housed but not paired-housed rats. Response rates of food-sated rats under increasing fixed-ratio requirements were higher for palatable food than for social interaction. The rats strongly preferred palatable food over social interaction and showed dose-dependent preference for social interaction vs. remifentanil.

CONCLUSIONS

We identified parameters influencing the reinforcing effects of operant social interaction and introduce a choice procedure sensitive to remifentanil self-administration dose.

Effects of Limited and Extended Pavlovian Training on Devaluation Sensitivity of Sign- and Goal-Tracking Rats

Individual differences in Pavlovian approach predict differences in devaluation sensitivity. Recent studies indicate goal-tracking (GT) rats are sensitive to outcome devaluation while sign-tracking (ST) rats are not. With extended training in Pavlovian lever autoshaping (PLA), GT rats display more lever-directed behavior, typical of ST rats, suggesting they may become insensitive to devaluation with more Pavlovian training experience. Here, we use a within-subject satiety-induced outcome devaluation procedure to test devaluation sensitivity after limited and extended PLA training in GT and ST rats. We trained rats in PLA to determine GT and ST groups. Then, we sated rats on either the training pellets (devalued condition) or homecage chow (valued condition) prior to brief non-reinforced test sessions after limited (sessions 5/6) and extended (sessions 17/18) PLA training. GT rats decreased conditioned responding under devalued relative to valued conditions after both limited and extended training, demonstrating they are sensitive to satiety devaluation regardless of the amount of PLA training. While ST rats were insensitive to satiety devaluation after limited training, their lever directed behavior became devaluation sensitive after extended training. To determine whether sign-tracking rats also displayed sensitivity to illness-induced outcome devaluation after extended training, we trained a separate cohort of rats in extended PLA and devalued the outcome with lithium chloride injections after pellet consumption in the homecage. ST rats failed to decrease conditioned responding after illness-induced outcome devaluation, while Non-ST rats (GT and intermediates) were sensitive to illness-induced outcome devaluation after extended training. Together, our results confirm devaluation sensitivity is stable in GT rats across training and devaluation approaches. Extended training unmasks devaluation sensitivity in ST rats after satiety, but not illness-induced devaluation, suggesting ST rats respond appropriately by decreasing responding to cues during state-dependent but not inference-based devaluation. The differences in behavioral flexibility across tracking groups and devaluation paradigms have translational relevance for the understanding state- vs. inference-based reward devaluation as it pertains to drug addiction vulnerability.

[VIVOPTIM: Feedback of an e-Health experimental program of primary prevention of cardiovascular risk on 30 to 70 years old volunteers]

Today by the e-health and the telemedicine, many people are more and more interested by the improvement of disease knowledge on cardiovascular diseases and associated risk factors, personalized self management support follow-up and e-Health monitoring. MGEN is a not-for-profit complementary health insurance gave itself the ways to use the new digital tools in health. MGEN developed an original and personalized program VIVOPTIM for the primary prevention of the cardiovascular risks for their members. The VIVOPTIM Pilot program is based upon digital services and was experimented by November 2015 to December, 2017 with 8000 members of the MGEN, from 30 to 70 years old and resident in two French areas (Occitanie and Bourgogne Franche-Comté). The assessment of the experiment VIVOPTIM e -health program was positive for the personalized cardiovascular support and for their health. Therefore, the MGEN generalized the VIVOPTIM program of cardiovascular prevention, to the whole France on July 11th, 2018.

[Evaluation of continuing medical training in private sector French cardiologists in 1999]

The authors present the results of a retrospective national enquiry which took place in 1999 and was mailed and faxed to the 3,800 cardiologists practising in the private sector in order to assess the different types of continuous, individual and collective postgraduate training which they had benefited from in the preceding 12 months. The data was analysed by comparison with that obtained from an individualized representative sample in a panel of private sector cardiologists. The results were then compared with the criteria of a yardstick proposed by the National Committee of Continuous Medical Education of 1997, according to the April 25th 1996 decree. The meeting of these criteria would require carrying out 114,000 to 76,000 hour-equivalents of continuous education whereas the present offer is about 100,000 hour-equivalents. The different forms of individual or collective training were compared in the 327 questionnaires which were exploitable following adhesion to the French Society of Cardiology, to the Cardiologists' Union, to local cardiological societies, by age, gender and type of practice. The average number of annual hours of collective education was 52.2 +/- 60.1 hours (25% quartile = 25 hours, 75% = 60 hours). The average value of hours of individual education was 89.7 +/- 89.3 hours (25% quartile = 25 hours; 75% = 120 hours). This evaluation indicates that about 15% of cardiologists practising in the private sector have inadequate continuous medical education and that 68% would satisfy the criteria laid down in 1997. Moreover, the present offer would seem to be adequate providing the criteria of accreditation have been met.