Infusions of scopolamine in dorsal hippocampus reduce anticipatory responding in an appetitive trace conditioning procedure

Pezze, M.A.; Marshall, H.J.; Cassaday, H.J.

Abstract

Trace conditioning is impaired by lesions to dorsal hippocampus, as well as by treatment with the muscarinic acetylcholine antagonist scopolamine. However, the role of muscarinic receptors within hippocampus has received little attention. The present study examined the effects of intra-hippocampal infusion of scopolamine (30?g/side) in an appetitive trace conditioning procedure using sucrose pellets as the unconditioned stimulus (US). This treatment resulted in reduced responding to a trace conditioned stimulus (CS), an effect most clearly seen when the US was presented at a 2s trace (inter-stimulus-interval, ISI). Intra-hippocampal scopolamine similarly depressed responding within the ISI (at both 2 and 10s trace intervals), but there was no such effect in the inter-trial-interval (ITI). There was also some overall reduction in responding when the US was delivered; significant at the 10s but not at the 2s trace interval. A similar pattern of results to that seen in response to the CS during acquisition was shown drug-free (in the 5s post-CS) in the extinction tests of conditioned responding. Moreover, in a different apparatus, locomotor activity was increased under scopolamine. Thus the results suggest that non-specific changes in activity or motivation to respond for the US cannot explain the reduction in trace conditioning as measured by reduced CS responding and in the ISI. Rather the findings of the present study point to the importance of associative aspects of the task in determining its sensitivity to the effects of scopolamine, suggesting that muscarinic receptors in the hippocampus are important modulators of short-term working memory.

Citation

Pezze, M., Marshall, H., & Cassaday, H. (2018). Infusions of scopolamine in dorsal hippocampus reduce anticipatory responding in an appetitive trace conditioning procedure. Brain and Behavior, https://doi.org/10.1002/brb3.1147

• Journal Article Type: Article
• Acceptance Date: Sep 28, 2018
• Online Publication Date: Oct 31, 2018
• Publication Date: Oct 31, 2018
• Deposit Date: Oct 1, 2018
• Publicly Available Date: Oct 31, 2018
• Print ISSN: 2162-3279
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Article Number: e01147
• DOI: https://doi.org/10.1002/brb3.1147
• Keywords: scopolamine; dorsal hippocampus; trace conditioning; rat
• Public URL: https://nottingham-repository.worktribe.com/output/1139941
• Publisher URL: https://onlinelibrary.wiley.com/doi/abs/10.1002/brb3.1147