Incentive-salience attribution is attenuated in spontaneously hypertensive rats, an animal model of ADHD.

Spontaneously Hypertensive Rats (SHR) have been extensively studied as an animal model of Attention Deficit Hyperactivity Disorder (ADHD) because they show some of the defining features of that disorder, like some forms of impulsivity and hyperactivity. However, other characteristics of the disorder, like a deficit in motivation, have been scarcely studied in the SHR strain. In the present report, we studied in 45 SHR and 45 Wistar rats as a comparison group, the capacity of attribution of incentive salience to a stimulus predictor of reinforcement, which has become a central concept in the study of motivation. We employed the Pavlovian Conditioned-Approach (PCA) task, in which a lever is presented 8 s before a pellet is delivered. The attribution of incentive salience is indicated by responses to the lever, in contrast to the absence of attribution of incentive salience, which is indicated by entrances to the pellet receptacle. For quantifying the attribution of incentive salience, we employed the PCA index, which integrates three related variables for each type of response, lever presses and entrances to the feeder: 1) the number of responses, 2) the latency to the first response, and 3) the probability that at least one response occurred during the presence of the lever. SHR showed lower levels of PCA, suggesting a deficit in the attribution of incentive salience to the lever. This finding replicates the results reported by previous research that compared SHR's performance in the PCA task against that of Sprague-Dawley rats.

Spontaneously hypertensive rats show higher impulsive action, but equal impulsive choice with both positive and aversive consequences.

Both positive and aversive delayed consequences play an important role in decision making. However, most of research has studied the temporal discounting of the positive consequences, while the study of the aversives is scarce in general and null in some areas. This is the case of research on impulsivity in spontaneously hypertensive rats (SHR), an animal model of ADHD. To evaluate SHRs' sensitivity to aversive delayed consequences, we employed a choice procedure in which subjects chose between a smaller-amount alternative and a larger-amount alternative plus a shock; when preference for the smaller-amount alternative stabilized, five different delays to the shock were presented with the objective of analyzing the recovery of preference for the larger-amount alternative, which is related to the sensitivity to the delayed aversive consequence. To analyze the sensitivity to delayed positive consequences we employed a procedure that evaluated the preference between a smaller-amount alternative and a larger-amount alternative as a function of the delay to the later. Finally, to evaluate impulsive action we employed a DRL 10 s schedule. In all tasks, Wistar rats were evaluated as control strain. The results indicated that choice impulsivity was equivalent between strains, both for positive and for aversive consequences. In contrast, we found a higher level of impulsive action in SHR.