Opposing effects on muscarinic acetylcholine receptors in the piriform cortex of odor-trained rats.

Full Abstract

We combined pharmacological studies and electrophysiological recordings to investigate modifications in muscarinic acetylcholine (ACh) receptors (mAChR) in the rat olfactory (piriform) cortex, following odor-discrimination rule learning. Rats were trained to discriminate between positive and negative cues in pairs of odors, until they reached a phase of high capability to learn unfamiliar odors, using the same paradigm ("rule learning"). It has been reported that at 1-3 d after the acquisition of odor-discrimination rule learning, pyramidal neurons in the rat piriform cortex show enhanced excitability, due to a reduction in the spike-activated potassium current I(AHP), which is modulated by ACh. Further, ACh and its analog, carbachol (CCh), lost the ability to reduce the I(AHP) in neurons from trained rats. Here we show that the reduced sensitivity to CCh in the piriform cortex results from a decrease in the number of mAChRs, as well as a reduction in the affinity of the receptors to CCh. Also, it has been reported that 3-8 d after the acquisition of odor-discrimination rule learning, synaptic transmission in the piriform cortex is enhanced, and paired-pulse facilitation (PPF) in response to twin stimulations is reduced. Here, intracellular recordings from pyramidal neurons show that CCh increases PPF in the piriform cortex from odor-trained rats more than in control rats, suggesting enhanced effect of ACh in inhibiting presynaptic glutamate release after odor training.

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Author information

Author/s: Saar, Drorit (D); Dadon, Moran (M); Leibovich, Marcela (M); Sharabani, Hagar (H); Grossman, Yoram (Y); Heldman, Eliahu (E);

Affiliation: Department of Physiology, Faculty for Health Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel. drorit(-atsign-)bgu.ac.il

Journal and publication information

Publication Type: Journal Article

Journal: Learning & memory (Cold Spring Harbor, N.Y.) (Learn Mem), published in United States. (Language: eng)

Reference: 2007-Mar; vol 14 (issue 3) : pp 224-8

Dates: Created 2007/06/19; Completed 2007/07/03; Revised 2008/11/20;

PMID: 17353547, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Animals
Binding, Competitive
Carbachol - metabolism; pharmacology
Cholinergic Agonists - metabolism; pharmacology
Discrimination Learning - physiology
Electrophysiology
Male
N-Methylscopolamine - metabolism

N-Methylscopolamine - metabolism
Neurons - drug effects; physiology
Odors
Olfactory Pathways - cytology; drug effects; metabolism; physiology
Pyramidal Cells - drug effects; physiology
Rats
Rats, Sprague-Dawley
Receptors, Muscarinic - metabolism

Associated Chemicals: Cholinergic Agonists (0) ; Receptors, Muscarinic (0) ; N-Methylscopolamine (13265-10-6) ; Carbachol (51-83-2)

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