Effects of an ethanol-paired CS on responding for ethanol and food: Comparisons with a stimulus in a Truly-Random-Control group and to a food-paired CS on responding for food

Abstract

Motivational increases due to exposure to alcohol-paired Conditioned Stimuli (CS) are central to some accounts of alcoholism. However, few studies isolate a stimulus’s function as a CS from its other potential functions. Pavlovian-Instrumental-Transfer (PIT) procedures isolate a stimulus’s function as a CS from its other functions. Though there are several relevant studies using PIT, knowledge gaps exist. Particularly, it is not clear that an alcohol-paired CS will increase alcohol seeking compared to the same stimulus in a Truly-Random-Control group, nor whether such increases are specific to alcohol seeking. To address these knowledge gaps in Experiment 1, rats responded for ethanol (0.1 ml 8% w/v) under an RI 30-sec schedule, then the lever was removed and half the rats had ethanol delivered during occasional 120-sec light presentations, while the remainder had ethanol and the light presented under independent RT schedules. Later the lever was returned and the light was presented during responding in extinction (PIT test). Following this test, levers were again removed and the light was presented without ethanol (light extinction), following again by a PIT test. Responding in the two groups during light presentations did not differ in either PIT test. Experiment 2 repeated Experiment 1 using food instead of ethanol. In Experiment 2, responding during light presentations increased in the paired group. In Experiment 3, rats were trained on a concurrent FR schedule of food and ethanol delivery. Ethanol was delivered following 5 responses and the response requirement for food adjusted so that similar numbers of food and ethanol deliveries were obtained. Subsequently, rats underwent conditioning, control and testing procedures identical to those in Experiment 1. In Experiment 3, the ethanol-paired CS increased ethanol-responding, but not food-responding. These results are most easily interpreted as changes in responding resulting from CS-elicited behavior rather than motivational changes. This interpretation is more compatible with some descriptions of the role of an alcohol-paired CS in alcoholism than others.

Conditioned Stimulus Form Does Not Explain Failures to See Pavlovian‐Instrumental‐Transfer With Ethanol‐Paired Conditioned Stimuli

“…This argues against these results of experiment 2 being PIT. Overall, these results suggest that our previous failure to see PIT with an ethanol-paired CS (Lamb et al 2016a) was neither a false negative nor a function of the form of the CS used. Other results from our previous study also buttress this assertion.…”

“…It is also important to note that at least two findings in our earlier report (Lamb et al 2016a) argue against the possibility of CS form being responsible for the lack of PIT. First, we replicated that experiment using food instead of ethanol and found PIT.…”

“…Eight rats were used in Experiment 1 that replicated the results of our previous experiment examining PIT with a 120-s light CS with rats responding under an Random Interval (RI) schedule of ethanol delivery (Lamb et al 2016a). Sixteen rats were used in Experiment 2 that was similar to the experiment of Krank (2003) using 10-s light CSs that were located either over the response lever or away from the lever with rats also responding under an RI schedule of ethanol delivery.…”

“…Procedures in Experiment 1 were similar to those in Experiment 1 of Lamb et al (2016a) for the paired group in that experiment.…”

“…In PIT, the response – reinforcer (or Unconditioned Stimulus; US) relationship and the Conditioned Stimulus (CS) – US relationship are trained separately, and then the effects of the CS upon responding is examined when both the response – reinforcer and the CS – US relationships are in extinction. We recently conducted two studies examining PIT using an ethanol-paired CS (Lamb et al 2016a). In one of these studies, we found PIT; that is, the CS increased responding for ethanol.…”