期刊
JOURNAL OF NEUROPHYSIOLOGY
卷 116, 期 2, 页码 825-843出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/jn.00110.2016
关键词
vestibular; semicircular canals; crista ampullaris; infrared neural stimulation; heat pulse; thermal excitability
资金
- National Institute on Deafness and Other Communication Disorders (NIDCD) [R01DC011481, R01DC006685]
- Medical Research Council of Australia [1048232]
- University of Newcastle International Visiting Research Fellowship
- Lockheed Martin Aculight
- National Institutes of Health (NIH) [R01DC009255, R01DC002390]
- NIH Training Grant [T32000023]
In the present study we combined electrophysiology with optical heat pulse stimuli to examine thermodynamics of membrane electrical excitability in mammalian vestibular hair cells and afferent neurons. We recorded whole cell currents in mammalian type II vestibular hair cells using an excised preparation (mouse) and action potentials (APs) in afferent neurons in vivo (chinchilla) in response to optical heat pulses applied to the crista (Delta T approximate to 0.25 degrees C per pulse). Afferent spike trains evoked by heat pulse stimuli were diverse and included asynchronous inhibition, asynchronous excitation, and/or phase-locked APs synchronized to each infrared heat pulse. Thermal responses of membrane currents responsible for APs in ganglion neurons were strictly excitatory, with Q(10) approximate to 2. In contrast, hair cells responded with a mix of excitatory and inhibitory currents. Excitatory hair cell membrane currents included a thermoelectric capacitive current proportional to the rate of temperature rise (dT/dt) and an inward conduction current driven by Delta T. An iberiotoxin-sensitive inhibitory conduction current was also evoked by Delta T, rising in <3 ms and decaying with a time constant of similar to 24 ms. The inhibitory component dominated whole cell currents in 50% of hair cells at -68 mV and in 67% of hair cells at -60 mV. Responses were quantified and described on the basis of first principles of thermodynamics. Results identify key molecular targets underlying heat pulse excitability in vestibular sensory organs and provide quantitative methods for rational application of optical heat pulses to examine protein biophysics and manipulate cellular excitability.
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