The degree to which delayed outcomes are devalued (delay discounting) is correlated with substance abuse and pathological gambling in humans. Recent evidence suggests that high rates of delay discounting are predictive of drug taking in laboratory animals and the present proposal will examine if a similar relation exists between delay discounting and the decision to gamble. Specifically, we will test the quantitative predictions of an empirically supported quantitative model of delay discounting which predicts that degree of delay discounting should be predictive of preference for gambling outcomes - individuals that discount delayed rewards to a greater degree should be more likely to gamble than those who discount these rewards to a lesser extent. Experiment 1 will test this prediction by first quantifying delay discounting in three rat strains, two of which are known to differ in 5-HT and dopamine system functioning. Then we will examine if these strain differences in degree of delay discounting are predictive of subsequent preferences for gambling when these choices result in economic losses. Experiment 2 will investigate the role of pramipexole and PD 128 907 (two selective D3 agonists) on Wistar rats' degree of delay discounting and preferences for gambling. Recent clinical evidence suggests that some Parkinson patients treated with pramipexole experience pathological levels of a variety of addictive behaviors, including gambling. Experiment 3 will examine if a form of delay tolerance training that has proven effective in pigeons and humans can decrease impulsive choices in a particularly impulsive rat strain (Lewis) when compared with a control group of Lewis rats given sham training. If so, then we will determine if the delay-tolerance-trained group chooses to gamble less than the sham-trained group.
Humans and nonhumans alike discount the value of delayed outcomes relative to immediate outcomes. This discounting process is correlated with substance abuse and pathological gambling. The proposed research will examine biological, pharmacological, and therapeutic variables that may affect delay discounting and the development of human pathological gambling.
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