Effects of sodium nitrite on DRL performance in the rat

Ffteen Sprague-Dawley rats were administered sodium nitrite 0.13% or 0.15% solutions in their drinking water from the age of 45 days to the end of the study. Six control rats received only tap water. At 80 days of age, rats were trained to bar press for food pellets on a CRF schedule. After reaching criterion performance the rats were switched to a DRL-20 for a period of 6 days to test for response inhibition, which was measured as a ratio of responses to reinforcements. Results indicated no significant differences between groups for response inhibition. All groups showed significant increases in learning as reflected by a decrease in ratios and an increase in total reinforcements over days. However, sodium nitrite rats compared to controls obtained significantly fewer reinforcements over sessions and a greater number of no responding periods (time-outs). One interpretation discussed was the possibility that sodium nitrite produced an increase in responding to distractible (non-task related) cues.