On 2014 Nov 10, Serge Ahmed commented:

This is an interesting series of experiments on choice between nicotine and sucrose in rats. In experiments 1, 3, 4 & 5, hungry rats were first trained to respond for sucrose or nicotine on alternate days before being provided with a choice between the two options. Overall, virtually all rats responded more for sucrose than for nicotine under a variety of choice conditions. Thus, all else being (approximately) equal, sucrose surpasses nicotine reward in rats!

In experiment 2, rats were first trained to respond for nicotine before being provided with a choice between nicotine and sucrose. In this condition, about 50% of the rats responded more for nicotine than for sucrose, suggesting that “nicotine self-administration does not only occur in the absence of alternative reinforcement options”, at least in some rats.

Though the results of experiment 2 are promising, they are difficult to interpret univocally. Experiment 2 lacks an important control group that controls for the difficulty in learning to respond for sucrose during choice testing. Briefly, rats were asked to respond on a novel lever under a random ratio 4 schedule of sucrose reinforcement, WITHOUT ANY PRIOR PROGRESSIVE TRAINING on this lever and after a long period of operant extinction. It is likely that many rats will fail to learn to respond for sucrose under these specific conditions, even in the absence of the opportunity to self-administer nicotine! Future research should resolve this important issue.

On 2014 Nov 10, Serge Ahmed commented:

This is an interesting series of experiments on choice between nicotine and sucrose in rats. In experiments 1, 3, 4 & 5, hungry rats were first trained to respond for sucrose or nicotine on alternate days before being provided with a choice between the two options. Overall, virtually all rats responded more for sucrose than for nicotine under a variety of choice conditions. Thus, all else being (approximately) equal, sucrose surpasses nicotine reward in rats!

In experiment 2, rats were first trained to respond for nicotine before being provided with a choice between nicotine and sucrose. In this condition, about 50% of the rats responded more for nicotine than for sucrose, suggesting that “nicotine self-administration does not only occur in the absence of alternative reinforcement options”, at least in some rats.

Though the results of experiment 2 are promising, they are difficult to interpret univocally. Experiment 2 lacks an important control group that controls for the difficulty in learning to respond for sucrose during choice testing. Briefly, rats were asked to respond on a novel lever under a random ratio 4 schedule of sucrose reinforcement, WITHOUT ANY PRIOR PROGRESSIVE TRAINING on this lever and after a long period of operant extinction. It is likely that many rats will fail to learn to respond for sucrose under these specific conditions, even in the absence of the opportunity to self-administer nicotine! Future research should resolve this important issue.