Nicotine does not produce state-dependent effects on learning in a Pavlovian appetitive goal tracking task with rats

Abstract

Past research has shown that when rats received 0.4mg base/kg nicotine paired reliably with intermittent sucrose delivery that anticipatory sucrose-seeking behavior (i.e., goal tracking) was differentially displayed in the nicotine state relative to intermixed saline sessions in which no sucrose was delivered. The present research extended this observation to a lower dose of nicotine (i.e., 0.2mg base/kg) and tested a state-dependent learning account of differential conditioned responding. According to this account, the increase in goal tracking on nicotine sessions reflects a chamber-sucrose association that is only recalled when in the nicotine state. We used a 2x2 factorial design in which rats received sucrose deliveries in one drug state (nicotine or saline) and were then tested in the same state (Nic-->Nic or Sal-->Sal) or a different state (Nic-->Sal or Sal-->Nic) after acquiring the conditioned response. A state-dependency account predicts disruption in conditioned goal tracking for rats that receive a shift in drug state on the test day. This disruption did not occur suggesting that differential control of conditioned responding by nicotine is more likely due to a direct excitatory association between the interoceptive cueing effects of nicotine and the appetitive qualities of sucrose.

Figure 1

Panel A displays the mean dipper entries per second across the course of discrimination training for the 0.2 mg/kg nicotine sessions and the saline sessions for Experiment 1. For nicotine sessions, the dipper entries come from the time before the first sucrose delivery; a comparable time was used for saline sessions. Panel B shows general chamber activity (beam breaks per second derived from the same interval as dipper entries) across discrimination training for nicotine and saline sessions.

Figure 2

Panel A displays the mean dipper entries per second across acquisition training for nicotine- and saline-trained rats in the state-dependency experiment. Panel B displays general chamber activity (beam breaks per second) for the same rats.

Figure 3

Panel A displays dipper entries per second during the first two minutes of the test session for Nicotine→Nicotine, Nicotine→Saline, Saline→Saline, and Saline→Nicotine groups of Experiment 2. Panel B displays general chamber activity (beam breaks per second) during the first two minutes of the test session for Nicotine→Nicotine, Nicotine→Saline, Saline→Saline, and Saline→Nicotine groups.

Figure 4

Panel A displays dipper entries per minute across the test session for Nicotine→Nicotine and Nicotine→Saline rats of Experiment 2. Panel B displays dipper entries per minute across the test session for Saline→Saline and Saline→Nicotine rats. Panel C displays general chamber activity across the test session for Nicotine→Nicotine and Nicotine→Saline rats. Panel D displays activity per minute across the test session for Saline→Saline and Saline→Nicotine rats.