title: Cholinergic, but not NMDA, receptors in the lateral entorhinal cortex mediate acquisition in trace eyeblink conditioning.
abstract: Anatomical and electrophysiological studies collectively suggest that the entorhinal cortex consists of several subregions, each of which is involved in the processing of different types of information. Consistent with this idea, we previously reported that the dorsolateral portion of the entorhinal cortex (DLE), but not the caudomedial portion, is necessary for the expression of a memory association between temporally discontiguous stimuli in trace eyeblink conditioning (Morrissey et al. (2012) J Neurosci 32:5356-5361). The present study examined whether memory acquisition depends on the DLE and what types of local neurotransmitter mechanisms are involved in memory acquisition and expression. Male Long-Evans rats experienced trace eyeblink conditioning, in which an auditory conditioned stimulus (CS) was paired with a mildly aversive electric shock to the eyelid (US) with a stimulus-free interval of 500 ms. Immediately before the conditioning, the rats received a microinfusion of neuroreactive substances into the DLE. We found that reversible inactivation of the DLE with GABAA receptor agonist, muscimol impaired memory acquisition. Furthermore, blockade of local muscarinic acetylcholine receptors (mACh) with scopolamine retarded memory acquisition while blockade of local NMDA receptors with APV had no effect. Memory expression was not impaired by either type of receptor blocker. These results suggest that the DLE is necessary for memory acquisition, and that acquisition depends on the integrity of local mACh receptor-dependent firing modulation, but not NMDA receptor-dependent synaptic plasticity.
authors: Department of Psychology, Toronto, Canada.
authors: Stephanie E
authors: SE
authors: Tanninen
authors: Department of Psychology, Toronto, Canada.
authors: XiaoTian
authors: X
authors: Yu
authors: Department of Psychology, Toronto, Canada.
authors: Thamy
authors: T
authors: Giritharan
authors: Department of Psychology, Toronto, Canada.
authors: Lina
authors: L
authors: Tran
authors: Department of Psychology, Toronto, Canada.
authors: Rami
authors: R
authors: Bakir
authors: Department of Psychology, Toronto, Canada.
authors: Julien
authors: J
authors: Volle
authors: Department of Psychology, Toronto, Canada.|Neuroscience Program, University of Toronto, Toronto, Canada.
authors: Mark D
authors: MD
authors: Morrissey
authors: Department of Psychology, Toronto, Canada.|Neuroscience Program, University of Toronto, Toronto, Canada.|Department of Cell and Systems Biology, Toronto, Canada.
authors: Kaori
authors: K
authors: Takehara-Nishiuchi
mesh_terms: D000818:Animals; D003215:Conditioning, Eyelid / Q000187:drug effects / Q000502:physiology*; D018728:Entorhinal Cortex / Q000187:drug effects / Q000502:physiology*; D058785:GABA-A Receptor Agonists / Q000494:pharmacology*; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009118:Muscimol / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D011950:Receptors, Cholinergic / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D012601:Scopolamine / Q000494:pharmacology
chemical_list: D058785:GABA-A Receptor Agonists; D018727:Muscarinic Antagonists; D011950:Receptors, Cholinergic; D016194:Receptors, N-Methyl-D-Aspartate; D009118:Muscimol; D012601:Scopolamine
keywords: entorhinal cortex; eyeblink conditioning; rats; reversible inactivation; trace conditioning