Comparison of ?9-THC, LSD-25 and scopolamine on non-spatial single alternation performance in the runway

Rats were trained in a straight runway on a non-spatial single alternation (NSSA) which involved presentation of reward (R) and nonreward (N) in a fixed repeating sequence (i.e. R-N-R-N ...). Patterned running results since rats learned to run fast on R trials and slow on N trials. This task can be regarded as an animal analog of the goal directed serial alternation task employed with humans. After patterned running was well established the effects of graded doses of δ9-THC, LSD and scopolamine were delineated. Although all drugs modified alternation performance, each agent produced distinctly specific effects on the different components of NSSA. δ9-THC disrupted alternation by decreasing running speed on R trials and increasing running speed on N trials. Lower doses of LSD increased running speed on N trials while leaving R trial speeds unchanged. At the highest dose, LSD decreased running speed on R trials while leaving N trial speeds only slightly elevated from baseline. Scopolamine disrupted alternation solely by decreasing speed on R trials. The results were discussed with reference to the effects of these drugs on internal inhibition, registration and recall of internal cues and timing behavior.