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

Drorit Saar, Moran Dadon, Marcela Leibovich, Hagar Sharabani, Yoram Grossman, Eliahu Heldman

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

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 IAHP 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.

Original languageEnglish
Pages (from-to)224-228
Number of pages5
JournalLearning and Memory
Volume14
Issue number3
DOIs
StatePublished - 1 Mar 2007

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