Koffarnus, M.N. & Woods, J.H. (2008).
Quantification of drug choice with the generalized matching law in rhesus monkeys.
Journal of the Experimental Analysis of Behavior, 89, 209-224.
The generalized matching law provides precise descriptions of choice,
but has not been used to characterize choice between different doses of
drugs or different classes of drugs. The current study examined rhesus monkeys’
drug self-administration choices between identical drug doses, different doses,
different drugs (cocaine, remifentanil, and methohexital), and between drug and
drug-paired stimuli. The bias parameter of the generalized matching law was used
to quantify preference for one reinforcer over another. Choice between identical
drug doses yielded undermatching. Choices between 0.3 µg/kg/injection remifentanil
and either 0.1 µg/kg/injection remifentanil or saline plus drug-paired stimuli
revealed bias for the 0.3 µg/kg/injection dose. Choice was relatively insensitive
to differences in random interval schedule value when one reinforcer was replaced with
drug-paired stimulus presentations. Bias for 0.3 µg/kg/injection remifentanil over
10 µg/kg/injection cocaine was seen in one subject, and indifference
was generally observed between 0.1 µg/kg/injection remifentanil and 56
µg/kg/injection cocaine and between 30 µg/kg/injection cocaine and
320 µg/kg/injection methohexital. These findings suggest the bias parameter
may be useful in quantitatively measuring level of preference, which would be
an advantage over concurrent FR procedures that often result in exclusive choice.
Key words: matching law, self-administration, remifentanil, cocaine,
methohexital, lever press, rhesus monkeys