Differential effects of corticotropin-releasing factor and acute stress on different forms of risk/reward...

Acute stress and corticotropin-releasing factor (CRF) have been show to perturb cost/benefit decision making involving effort costs. However, previous studies on how stress manipulations affect decisions involving reward uncertainty have yielded variable results. To provide additional insight into this issue, the current study investigated how central CRF infusion and acute restraint stress alter different forms of risk/reward decision-making guided by internal representations of risk/reward contingencies or external informative cues. Male rats were well-trained on one of two tasks that required choice between a small/certain or a large/risky reward. On a probabilistic discounting task, the probability of obtaining the larger reward increased or decreased systematically over blocks of trials (100-6.25%). On a cue-guided Blackjack task, reward probabilities (50% or 12.5%) were signaled by discriminative auditory cues. CRF (1 or 3 μg) was infused intracerebroventricularly (ICV) or one-hour of restraint stress was administered prior to behavioral testing. Neither CRF nor acute stress altered risky choice on probabilistic discounting, but did increase trial omissions in the latter part of the session. Conversely on the Blackjack task, CRF reduced risky choice on good-odds trials (50%), whereas acute stress increased reward sensitivity. CRF but not acute stress also slowed decision latencies across tasks. These data reveal complex and differential manners in which increased CRF activity and acute stress alter distinct forms of risk/reward decision-making, particularly those guided by external cues.