Trying to make sense of rodents’ drug choice behavior

Serge H. Ahmed
Progress in Neuro-Psychopharmacology and Biological Psychiatry. 2018-12-01; 87: 3-10
DOI: 10.1016/j.pnpbp.2017.09.027

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Since the first experimental hint for the existence of “an actual desire or
striving for the drug” in nonhuman animals by Sidney Spragg in the late 1930s,
much effort has been expended by lab researchers to try to model in a valid
manner the key behavioral aspects and signs of addiction in animals, typically in
rodents (i.e., mainly rats and, to a lesser extent, mice). Despite much advances,
there still remains a lingering doubt about the disordered status of drug use in
rodents. This is mainly because drug use occurs in a particular setting where
animals have access to a drug for self-administration but without access to other
valuable behavioral options that could compete with and divert from drug use.
Here I review evidence showing that enriching the drug setting with other
behavioral options can dramatically influence the pattern of drug choices in
rodents. Overall, access to other options during drug access can divert the vast
majority of rats from continued drug use. Only few individuals continue to engage
in drug use despite access to and at the expense of other options. However, there
exist certain high-risk settings in which virtually all animals are vulnerable to
develop a harmful pattern of exclusive drug use that can even become fatal in the
long run if not discontinued by an outside intervention. Paradoxically, it
appears that the behavioral trait that is hypothesized to uniquely render rodents
vulnerable to the latter settings (i.e., a narrow focus on the local, current
choice, with no consideration of the global pattern of choice) would also protect
most of them from using drugs in other choice settings. I conclude with an
attempt to make sense of this peculiar setting-specific behavior and with some
general propositions for future research.


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