Banca de QUALIFICAÇÃO: AELTON SILVA ARAUJO

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : AELTON SILVA ARAUJO
DATE: 16/03/2023
TIME: 09:00
LOCAL: INSTITUTO DO CEREBRO
TITLE:

On the electrophysiological effects of sevoflurane on layer 5 pyramidal neurons of the mouse primary auditory cortex

KEY WORDS:

Sevoflurane; Primary auditory cortex; Layer 5; Pyramidal neurons; Firing properties;

PAGES: 42
BIG AREA: Ciências Biológicas
AREA: Fisiologia
SUMMARY:

General anesthetics are ubiquitous in medical practice, but the cellular mechanisms that promote amnesia, analgesia, immobility and unconsciousness by affecting voltage and ligand-gated ion channels still need to be better understood. Recent studies show that different anesthetics differentially affect specific ion channels and cortical pyramidal neurons are affected by lower concentrations than interneurons. This highlights that general anesthesia does not follow a "general" mechanism but depends on the choice of anesthetics and cell-type specific effects. Volatile anesthetics like sevoflurane are especially hard to study in in vitro preparations. Yet, biophysical models predict stabilization of the open-state of low-threshold voltage-gated K+ currents (Kv1.2 channels), yet to be confirmed by electrophysiology. Here we attempt a first step in identifying the electrophysiological profile of sevoflurane. We applied sevoflurane by passing the carbogen mixture through a vaporizer for volatile anesthetic thereby oxygenating and solubilizing sevoflurane in the recording artificial cerebral spinal fluid (aCSF) and performed whole-cell patch-clamp recordings of layer 5 pyramidal neurons (L5 PN) of the auditory cortex of adult mice. Concentrations of sevoflurane in the aCSF were quantified using gas chromatography-mass spectrometry. We subdivided L5 PN into type A and B cells based on active membrane properties in response to small depolarizing and hyperpolarizing current steps. Quantification of passive and active membrane properties before and after application of sevoflurane at 0.5% (30-50 µM in recording chamber) showed a decrease in the firing frequency for both cell types and a specific effect on depolarizing the action potential threshold of type A L5 PNs, (ΔAPthreshold=+15.62 mV; p=0.036; n=7) and increasing the latency of action potential half-width of type B L5 PNs (ΔAPHalf-width=+0.49 ms; p=0.0405; n=10). Stable recordings after washout of sevoflurane restored partially initial maximum firing frequency, AP threshold for type A and AP half-width for type B L5 PNs. Our preliminary results conclude that sevoflurane decreases the firing frequency of both types of L5 PNs. However, membrane properties are differentially affected depending on cell type. Future studies will also examine how sevoflurane alters membrane properties of different types of cortical interneurons and contribute to our cellular understanding of volatile anesthetics' mechanism of action.

COMMITTEE MEMBERS:
Interno - 1728817 - CLAUDIO MARCOS TEIXEIRA DE QUEIROZ
Interno - 3086031 - DANIEL YASUMASA TAKAHASHI
Presidente - 1976236 - EMELIE KATARINA SVAHN LEAO