Concurrent access to nicotine and sucrose in rats

Abstract

Background Animal models that allow concurrent access to drug and nondrug reinforcers provide unique insight into the etiology, maintenance, and treatment of drug use. Objectives We sought to develop and utilize a concurrent access procedure with nicotine and sucrose in rats. Methods Pressing one lever delivered intravenous nicotine, and pressing another lever delivered sucrose pellets, with both reinforcers freely available throughout daily sessions. Results Rats that had been pretrained with nicotine on some days and sucrose on other days responded on both levers when subsequently given concurrent access, but almost all responded at substantially higher rates on the sucrose lever. In contrast, rats pretrained exclusively with nicotine before being given concurrent access showed individual differences, with about half responding more on the nicotine lever. Treatment with the nicotinic receptor partial agonist varenicline selectively decreased nicotine self-administration. Food restriction and removal of the sucrose lever both increased nicotine self-administration. Conclusions The finding that rats continue to take nicotine when sucrose is concurrently available—and in many cases take it more frequently than sucrose—demonstrates that nicotine self-administration does not only occur in the absence of alternative reinforcement options. As a model of human nicotine use, concurrent access is more naturalistic and has higher face validity than procedures in which only one reinforcer is available or choosing one reinforcer precludes access to other reinforcers. As such, this procedure could be useful for evaluating therapeutic agents and improving our understanding of environmental conditions that promote or discourage nicotine use.

The effects of nicotine self-administration and withdrawal on concurrently available chow and sucrose intake in adult male rats

“…This is consistent with other studies demonstrating that concurrent access to sucrose and nicotine in limited access sessions does not decrease rates of NSA [50,51], unless sucrose availability is contingent upon abstaining from nicotine [50]. Moreover, rats in the present study showed robust NSA despite having ad libitum access to food, which is consistent with other studies showing that food deprivation is not required for nicotine to serve as a reinforce [52,53].…”

Choice between delayed food and immediate oxycodone in rats

“…In this respect, our results are similar to those of Ferguson and Paule (1995), who found that pre-session vs. post-session feeding had surprisingly little effect on already-established food responding. Pre-session feeding with chow also failed to affect choice between sweet food and nicotine in an earlier study, even though it decreased nicotine self-administration in a drug-only condition (Panlilio et al 2015). The fact that pre-session feeding with chow did not affect choice between food and oxycodone suggests that the motivation driving choice of food in these rats was specific to sweet pellets (Dickinson et al 1996).…”

The role of varenicline on alcohol-primed self-administration and seeking behavior in rats

“…Varenicline tartrate (Abcam Pharmaceuticals, Cambridge, UK) was dissolved in 0.9% saline solution which also served as the vehicle control. Doses for Experiments 1 and 2 were selected based on previous studies (Ginsburg and Lamb 2013; LeSage et al 2009; Panlilio et al 2014). Doses for Experiments 4 and 6 were determined based on the outcome of Experiments 1 and 2.…”