Biology subjects

Robinson, M. J. F.

Publications and source records attributed to Robinson, M. J. F..

2 recordsLinked to original sources

bioRxiv2024

Relapse after intermittent access to cocaine: Discriminative cues more effectively trigger drug seeking than do conditioned cues

When people with drug addiction encounter cues associated with drug use, this can trigger cravings and relapse. These cues can include conditioned stimuli (CSs) signaling drug delivery and discriminative stimuli (DSs) signaling drug availability. Compared to CS effects, DS effects are less explored in preclinical studies on cue-induced relapse. We compared CS and DS effects on reward seeking following abstinence from intermittent-access cocaine (or sucrose) self-administration. During 15-20 intermittent-access sessions, rats self-administered sucrose pellets or i.v. cocaine paired with a light-tone CS. Cocaine/sucrose was available for 5-min (signalled by a light; DS+) and unavailable for 25 min (signalled by different lighting conditions; DS-), and this cycled for 4 h/session. Following abstinence, we measured cocaine/sucrose seeking under extinction triggered by CS and DS presentation, and instrumental responding reinforced by these cues. Across intermittent-access sessions, rats increased lever pressing for cocaine or sucrose during DS+ periods and decreased responding during DS-periods. On days 2 and 21 of abstinence, only presentation of the DS+ or DS+ and CS combined elicited increased cocaine/sucrose-seeking behaviour (i.e., increased active lever presses). Additionally, presenting the DS-alongside the DS+ suppressed the increased cocaine-seeking behaviour otherwise produced by the DS+. Finally, on day 21 of abstinence, rats showed equivalent levels of lever pressing reinforced by the DS+, CS and by the DS+ and CS combined, suggesting comparable conditioned reinforcing value. After intermittent self-administration, cocaine-associated DSs and CSs acquire similar conditioned reinforcing properties, but DSs more effectively trigger increases in drug seeking.

animal behavior and cognition↗

bioRxiv2023

Uncertain, intermittent access to reward promotes increased reward pursuit

Self-administration procedures have been developed to model the intermittency of cocaine use in humans. These procedures involve intermittent, predictable access to cocaine during daily self-administration sessions. However, human drug use often involves intermittent and unpredictable patterns of drug access. Here, we introduce a new procedure to study the effects of unpredictable, intermittent access (UIntA) to a reinforcer, and we compare this procedure to two existing ones that provide predictable reinforcer availability; continuous (ContA) or intermittent (IntA) access. Three groups of rats self-administered water or a 5% sucrose solution in daily hour-long sessions. UIntA rats had alternating periods of reinforcer ON and OFF of unpredictable duration (1, 5 or 9 min/period). During reinforcer ON periods, reinforcer quantities were also unpredictable (0, 0.1 or 0.2 ml of solution) and were available under a variable ratio 3 schedule of reinforcement (1-6 responses). Both IntA and ContA rats had access to a fixed volume of water or sucrose (0.1 ml), under a fixed ratio 3 schedule of reinforcement. IntA rats had alternating and predictable 5-min reinforcer ON and OFF periods, while ContA rats had 60 minutes of reinforcer access during each session. Following 14 daily self-administration sessions, we found that UIntA rats had the highest rates of responding for water or sucrose reward under progressive ratio and extinction conditions, and the highest levels of cue-induced reinstatement of sucrose seeking. Thus, uncertain, intermittent access to reward promotes increased reward-seeking and -taking behaviours. This has implications for modeling addiction and other disorders of increased reward seeking.

neuroscience↗