Conditions sufficient for the production of oral cocaine or lidocaine self-administration in preference to water.

Groups of rats were given a chronic history of drinking cocaine solutions of different concentrations in daily, 3-h schedule induced polydipsia sessions. Animals failed to develop a preference for cocaine solution to concurrently presented water. Schedule-induction conditions were maintained, and the animals were divided into separate groups, drinking either cocaine or lidocaine placed in a highly acceptable vehicle (glucose-saccharin solution). Animals preferred their respective drug solutions to concurrently presented water, and these preferences remained stable after the glucose-saccharin vehicle was gradually faded to water, leaving only cocaine or lidocaine, respectively, in the solution. Thus a stable preference for drug solution to water could be instituted in rats for either cocaine or lidocaine solution (putative reinforcing and nonreinforcing agents, respectively) given an appropriate associative history, with high intakes maintained by schedule-induction. Conditions sufficient for the initiation of an oral preference and high intake for a putatively reinforcing drug cannot be assumed to occur owing to the drug's reinforcing property in the absence of demonstrating the ineffectiveness of an appropriate negative control substance.