title: Inhibition of TRPV1 channels enables long-term potentiation in the entorhinal cortex.
abstract: The transient receptor potential vanilloid 1 (TRPV1) channel is a non-selective cation channel that is mainly found in nociceptive neurons of the peripheral nervous system; however, these channels have also been located within the CNS, including the entorhinal cortex. Whole-cell patch-clamp recordings of principal entorhinal cortex (EC) layers II/III neurons revealed that evoked inhibitory postsynaptic currents were depressed by application of the TRPV1 agonist capsaicin (CAP), accompanied by a change in the pair-pulse ratio (PPR). In addition, recordings of miniature inhibitory postsynaptic currents (mIPSCs) revealed that inter-event intervals but not amplitude were decreased in wild-type (WT) after application of CAP. This suggests that TRPV1 channels are functional in the entorhinal cortex and are located on inhibitory neurons with their axonal arborization within layers II/III. In order to study TRPV1 channels and their involvement in long-term potentiation (LTP) induction in a more intact circuit, extracellular field potential recordings were performed in EC layers II/III. It was found that activated TRPV1 channels preclude induction of long-term potentiation. In sharp contrast, clear LTP was observed when antagonizing TRPV1 channels or recording from TRPV1 knock-out mice. Thus, these results suggests that signaling through activating inhibitory presynaptic TRPV1 channels represents a novel mechanism by which a shift in feed-forward inhibition of layers II/III cortical principal neurons prompt changes in synaptic strength and thereby contribute to a change of information storage within the brain.
authors.affiliation: Danish Neuroscience Centre, Aarhus University Hospital/Aarhus University, Nørrebrogade 44, Bygning 10G, 2.sal, 8000, Aarhus C, Denmark. tbanke@biomed.au.dk.
authors.forename: Tue G
authors.initials: TG
authors.lastname: Banke
mesh_terms: D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology; D018728:Entorhinal Cortex / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D025461:Feedback, Physiological; D053444:Inhibitory Postsynaptic Potentials; D017774:Long-Term Potentiation; D051379:Mice; D018689:Sensory System Agents / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000819:agonists / Q000235:genetics / Q000378:metabolism*
chemical_list: D018689:Sensory System Agents; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; D002211:Capsaicin
keywords: GABAergic transmission; Synaptic plasticity; TRPV1; Transient receptor potential channels