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

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


M.A. Pezze

H.J. Marshall

Professor of Behavioural Neuroscience


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.


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,

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
Keywords scopolamine; dorsal hippocampus; trace conditioning; rat
Public URL
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