Two kinds of Pavlovian conditioned approach behavior are possible: approach of the CS (signtracking) and approach of the US (goal-tracking). We hypothesized that administration of AMP would increase sign-tracking and decrease goal-tracking. However, increasing doses of AMP (up to 2.0 mg/kg) decreased measures of sign-tracking while simultaneously increasing measures of goaltracking. Administration of AMP may shift responding from cues distant from the CS to cues closer to the CS.
Keywordsamphetamine; sign-tracking; goal-tracking; rat; addiction; Pavlovian; acute
Differential Effects of Amphetamine on Sign-Tracking and Goal-TrackingA Pavlovian conditioned appetitive approach or autoshaping procedure typically involves presentation of a conditioned stimulus (CS) which is followed shortly afterward with presentation of an unconditioned stimulus (US) such as food. In such a procedure, the response of approaching or contacting the CS typically develops even though doing so does not affect US presentation [2], or in some cases, reduces or eliminates exposure to the appetitive US [7]. As Pavlovian conditioned responses have been implicated in the development and maintenance of drug addiction [2,4,6,8,22] understanding the fundamental mechanisms behind Pavlovian conditioning is relevant to the understanding of addiction and related phenomena.The nature of the conditioned approach response may change in a situation in which the location of the CS and the location where the US is delivered are separate and distinct. In the case where a CS in one location indicates delivery of reinforcement in another, the subject can make two kinds of conditioned response. The first, sign-tracking, involves approach/contact of the CS, whereas the second, goal-tracking,
Research on consolidation of long-term memory suggests that acute immune system activation induced by endotoxin lipopolysaccharide (LPS) may disrupt consolidation of newly acquired learning. Adult male Sprague-Dawley rats were trained to perform a simple Y-maze task and were immediately afterwards administered LPS (15 microg/kg) or saline. After a seven-day interval, subjects were returned to the Y-maze and were retrained to criterion. It was found that subjects treated with saline required significantly fewer trials to relearn the task relative to the LPS group and a no-partial-learning control group, which themselves did not differ. These results are most readily explained in terms of a disruptive effect of acute immune system activation on consolidation of newly induced acquired memories.
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