Habituation to a test apparatus during associative learning is sufficient to enhance muscarinic acetylcholine receptor-immunoreactivity in rat suprachiasmatic nucleus

EA Van der Zee*, B A M Biemans, M P Gerkema, S Daan

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

20 Citations (Scopus)
147 Downloads (Pure)

Abstract

The suprachiasmatic nucleus (SCN) is engaged in modulation of memory retention after (fear) conditioning, but it is unknown which pathways and neurotransmitter system(s) play a role in this action. Here we examine immunocytochemically whether muscarinic acetylcholine receptors (mAChRs), mediating cholinergic signal transduction in the SCN, are involved. For this purpose, mAChR immunoreactivity (mAChR-ir) was studied in the SCN after various stages of passive shock avoidance (PSA) and active shock avoidance (ASA) training and, for ASA, at various posttraining time points. mAChR-ir was significantly enhanced in SCN neurons as a result of the training procedure, and the number of mAChR-positive glial cells in the SCN increased significantly. The increase in mAChR-ir as a result of PSA and ASA training was not due to fear conditioning or the number of correct avoidances (in case of ASA training) but rather to behavioral arousal as a consequence of (brief) exposure to a novel environment (the test apparatus). This finding was confirmed by a cage-change experiment in which the rats were allowed to stay in a novel cage for 15 min or 24 hr. Only the brief exposure to the fresh cage triggered alterations for SCN mAChRs 24 hr later. These results shed new light on a possible function of the cholinergic system in the SCN mediated by mAChRs in relation to modulation of memory processes and demonstrate that behavioral arousal during (the habituation stage of) a learning task is sufficient to alter the mAChR system in the SCN. (C) 2004 Wiley-Liss, Inc.

Original languageEnglish
Pages (from-to)508-519
Number of pages12
JournalJournal of Neuroscience Research
Volume78
Issue number4
DOIs
Publication statusPublished - 15-Nov-2004

Keywords

  • active shock avoidance
  • cholinergic signal transduction
  • glial cells
  • novelty
  • passive shock avoidance
  • cage change
  • PASSIVE-AVOIDANCE
  • CIRCADIAN-RHYTHMS
  • RETENTION DEFICITS
  • PERIODIC INTERVALS
  • SYRIAN-HAMSTERS
  • PHASE-SHIFTS
  • BRAIN-STEM
  • AGED RATS
  • NEURONS
  • FOREBRAIN

Cite this