Conditioned drinking: a specific or nonspecific response?

Consumption of alcohol compared to another bitter solution in a limited access drinking paradigm

A number of recent studies have shown that free-feeding rats will consume pharmacologically significant amounts of alcohol when given access to alcohol for short periods of time daily. The present experiment was designed to examine the role of taste in inducing alcohol consumption in this type of periodic availability paradigm, by comparing amounts drunk thereby to amounts of another bitter solution, sucrose octa acetate (SOA), presented on a similar schedule. In contrast to alcohol, which was consistently preferred to water, at a concentration as high as 12% (w/v), preference for SOA diminished across days, indicating that the bitter taste alone was insufficient to increase consumption of this solution. The results also suggest the animals may be drinking in response to external conditioning stimuli, an effect which has previously been demonstrated in regard to feeding.

Conditioned thirst in rats

The purpose of these studies was to assess the appropriateness of control groups in previous thirst conditining studies and to demonstrate that conditioned drinking can be viewed as a classically conditioned appetitive response. In Experiment I (N = 48) thirst was conditioned by the procedure employed by Solomon and Swanson [see Mowrer (11)]. With the use of a "novel cage" group, suppression rather than enhancement of intake was obtained. These and other investigators' results were interpreted in the light of the appropriateness of control groups. In Experiment II (N = 30) rate demonstrated increased water intake at zero hours water deprivation in the presence of an external stimulus previously paired with an increasing motive state. Intakes monitored at half-hour intervals revealed that "low-to-high" drive associated stimuli did not affect overall intake but did induce differentiation in drinking patterns causing first enhancement and then reduction in intake amounts. The results were agreement with Seligman et al. (14) who suggested that elicitation of the prepared mechanism evokes drinking, but water regulation controls do not allow prolonged hyperdipsia.

Pavlovian conditioning of eating induced by spreading depression in cortex, striatum and hippocampus of rats

A single wave of unilateral spreading depression in the cortex, hippocampus or caudate nucleus of rats elicits eating after 2-6 min. The present experiments provide evidence that such spreading depression-induced eating can be classically conditioned to a complex conditioned stimulus. A wave of spreading depression was triggered by injection of 0.5-2.0 mul of 25 percent KCl solution. In a first experiment successful conditioning was demonstrated in 20 rats, involving 7 cortical, 5 caudate and 8 hippocampal spreading depression sites. Four animals failed to show any conditioned eating. A control group of 8 animals, in which cortical spreading depression did not induce eating, showed no increase in eating in the presence of the CS after conditioning trials. A second experiment, which included pseudoconditioning and NaCl control groups, confirmed the results obtained in Experiment 1. Classical conditioning was successful in 11 animals, involving 6 cortical and 5 caudate spreading depression sites. Neither the pseudoconditioning (14 animals, involving 8 cortical and 6 caudate spreading depression sites) not the NaCl control group (8 animals, all with cortical sites), showed eating in the presence of the CS. In both experiments the conditioned eating underwent gradual extinction.