title: An environment-dependent modulation of cortical neural response by forebrain cholinergic neurons in awake rat.
abstract: The forebrain cholinergic neurons project to cortex, including the hippocampus and the cingulate cortex (Cg). However, the relative influence of these neurons on behavior-linked neural processing in the two cortical areas remains unclear. We have now examined the effect of destruction of the cholinergic neurons with microinjection of the immunotoxin 192 IgG-saporin into the medial septum on the induction of c-Fos protein, an index of neuronal synaptic excitation, in the two forebrain areas to varied episodic experiences. Separate groups of rats were (a) re-exposed to the laboratory where they had previously undergone a surgery for intraseptal microinjection or (b) exposed to a novel environment. Re-exposure evoked a differential increase in the number of c-Fos positive neurons in dorsal CA1 compared to novelty, while a robust increase was observed in the Cg selectively in the novel environment. Both the differential and the selective increases were strongly attenuated by the cholinergic destruction with intraseptal-immunotoxin. These findings suggest that the cholinergic modulation of the neural processing in the two forebrain areas varies partly in an environment-dependent fashion affecting CA1 neural activation on repeat exposure to an environment where they had a relatively complex aversive experience while favoring Cg neural activation more during novelty.
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore.
authors.forename: Mohammed Zacky
authors.initials: MZ
authors.lastname: Ariffin
authors.forename: Lai Seong
authors.initials: LS
authors.lastname: Chang
authors.forename: Han Chow
authors.initials: HC
authors.lastname: Koh
authors.forename: Chian-Ming
authors.initials: CM
authors.lastname: Low
authors.forename: Sanjay
authors.initials: S
authors.lastname: Khanna
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D018678:Cholinergic Agents / Q000494:pharmacology; D059329:Cholinergic Neurons / Q000187:drug effects / Q000502:physiology*; D004777:Environment; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D008297:Male; D009068:Movement / Q000187:drug effects; D009434:Neural Pathways / Q000502:physiology; D016548:Prosencephalon / Q000166:cytology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D054789:Ribosome Inactivating Proteins, Type 1 / Q000494:pharmacology; D000076985:Saporins; D020665:Septum of Brain / Q000187:drug effects; D014851:Wakefulness
chemical_list: C085696:192 IgG-saporin; D000911:Antibodies, Monoclonal; D018678:Cholinergic Agents; D016760:Proto-Oncogene Proteins c-fos; D054789:Ribosome Inactivating Proteins, Type 1; D002795:Choline O-Acetyltransferase; D000076985:Saporins