title: Excitability and responsiveness of rat barrel cortex neurons in the presence and absence of spontaneous synaptic activity in vivo.
abstract: The amplitude and temporal dynamics of spontaneous synaptic activity in the cerebral cortex vary as a function of brain states. To directly assess the impact of different ongoing synaptic activities on neocortical function, we performed in vivo intracellular recordings from barrel cortex neurons in rats under two pharmacological conditions generating either oscillatory or tonic synaptic drive. Cortical neurons membrane excitability and firing responses were compared, in the same neurons, before and after complete suppression of background synaptic drive following systemic injection of a high dose of anaesthetic. Compared to the oscillatory state, the tonic pattern resulted in a more depolarized and less fluctuating membrane potential (Vm), a lower input resistance (Rm) and steeper relations of firing frequency versus injected current (F-I). Whatever their temporal dynamics, suppression of background synaptic activities increased mean Vm, without affecting Rm, and induced a rightward shift of F-I curves. Both types of synaptic drive generated a high variability in current-induced firing rate and patterns in cortical neurons, which was much reduced after removal of spontaneous activity. These findings suggest that oscillatory and tonic synaptic patterns differentially facilitate the input-output function of cortical neurons but result in a similar moment-to-moment variability in spike responses to incoming depolarizing inputs.
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, UPMC; INSERM U 1127; CNRS UMR 7225, Hôpital Pitié-Salpêtrière, F-75013, Paris, France.
authors.forename: Tristan
authors.initials: T
authors.lastname: Altwegg-Boussac
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, UPMC; INSERM U 1127; CNRS UMR 7225, Hôpital Pitié-Salpêtrière, F-75013, Paris, France.
authors.forename: Mario
authors.initials: M
authors.lastname: Chavez
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, UPMC; INSERM U 1127; CNRS UMR 7225, Hôpital Pitié-Salpêtrière, F-75013, Paris, France.
authors.forename: Séverine
authors.initials: S
authors.lastname: Mahon
authors.affiliation: Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, UPMC; INSERM U 1127; CNRS UMR 7225, Hôpital Pitié-Salpêtrière, F-75013, Paris, France UPMC Univ Paris 06, F-75005, Paris, France stephane.charpier@upmc.fr.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Charpier
mesh_terms: D000200:Action Potentials; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D005283:Fentanyl / Q000494:pharmacology; D018757:GABA Modulators / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010424:Pentobarbital / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*; D055366:Synaptic Potentials
chemical_list: D000701:Analgesics, Opioid; D018757:GABA Modulators; D010424:Pentobarbital; D005283:Fentanyl
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