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Latency of auditory evoked potential monitoring the effects of general anesthetics on nerve fibers and synapses.

Huang B, Liang F, Zhong L, Lin M, Yang J, Yan L, Xiao J, Xiao Z - Sci Rep (2015)

Bottom Line: Auditory evoked potential (AEP) is an effective index for the effects of general anesthetics.However, it's unknown if AEP can differentiate the effects of general anesthetics on nerve fibers and synapses.Therefore, we conclude that, AEP latency is superior to amplitude for the effects of general anesthetics, ∆L monitors the effect of hypothermia on nerve fibers, and ∆I monitors a combined effect of anesthesia and hypothermia on synapses.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, PR China [2] Department of Anesthesiology, Nanfang Hospital, Southern Medical University, Guangzhou 510515, PR China.

ABSTRACT
Auditory evoked potential (AEP) is an effective index for the effects of general anesthetics. However, it's unknown if AEP can differentiate the effects of general anesthetics on nerve fibers and synapses. Presently, we investigated AEP latency and amplitude changes to different acoustic intensities during pentobarbital anesthesia. Latency more regularly changed than amplitude during anesthesia. AEP Latency monotonically decreased with acoustic intensity increase (i.e., latency-intensity curve) and could be fitted to an exponential decay equation, which showed two components, the theoretical minimum latency and stimulus-dependent delay. From the latency-intensity curves, the changes of these two components (∆L and ∆I) were extracted during anesthesia. ∆L and ∆I monitored the effect of pentobarbital on nerve fibers and synapses. Pentobarbital can induce anesthesia, and two side effects, hypoxemia and hypothermia. The hypoxemia was not related with ∆L and ∆I. However, ∆L was changed by the hypothermia, whereas ∆I was changed by the hypothermia and anesthesia. Therefore, we conclude that, AEP latency is superior to amplitude for the effects of general anesthetics, ∆L monitors the effect of hypothermia on nerve fibers, and ∆I monitors a combined effect of anesthesia and hypothermia on synapses. When eliminating the temperature factor, ∆I monitors the anesthesia effect on synapses.

No MeSH data available.


Related in: MedlinePlus

Best frequencies of recording sites.(a) 80 dB pure tone bursts at 5–26 kHz evoked AEPs from a recording site. (b) An amplificatory sample shown in a 17 kHz panel to demonstrate AEP waveforms and the extracted parameters, i.e., latency and amplitude. The AEP (red line) was average line for 10 samples (gray lines) to the same acoustic stimulus. (c) Definition of BF. (d) Summary of best frequencies of all recording sites in twenty-five mice.
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f1: Best frequencies of recording sites.(a) 80 dB pure tone bursts at 5–26 kHz evoked AEPs from a recording site. (b) An amplificatory sample shown in a 17 kHz panel to demonstrate AEP waveforms and the extracted parameters, i.e., latency and amplitude. The AEP (red line) was average line for 10 samples (gray lines) to the same acoustic stimulus. (c) Definition of BF. (d) Summary of best frequencies of all recording sites in twenty-five mice.

Mentions: To identify the BF of a recording site, pure tone bursts of various frequencies at 80 dB SPL were delivered to the mice. For example, the AEP recorded with an electrode penetrated at 816 μm depth in ICC of a mouse M20110525, tuned to 5–26 kHz pure tone bursts (Fig. 1a). At each frequency, ten AEP waveforms (Fig. 1a, the gray lines) were averaged (Fig. 1a, the red line). Each average AEP waveform had P0, N1 and P1 waves (Fig. 1b, the red line). The time from the beginning of the acoustic stimulus to the N1 peak was defined as latency, and the voltage difference from the N1 peak to the P1 peak was defined as amplitude (Fig. 1b). From 5 to 26 kHz, the amplitudes to 80 dB acoustic stimuli (A80) first increased to a vertex at 14 kHz, and then decreased gradually (Fig. 1c). The frequency with the largest A80 was defined as BF. The mice were sorted by BF of the recording site. Mouse M20110525 is No. 9 with BF 14 kHz. The best frequencies of recording sites of twenty-five mice were 6–26 kHz (Fig. 1d), which were distributed in different locations of ICC. To obtain AEP latency and amplitude to different acoustic intensities, auditory evoked potentials to seven different acoustic intensities (from 30 to 90 dB in 10 dB steps) at BF in each recording session were recorded.


Latency of auditory evoked potential monitoring the effects of general anesthetics on nerve fibers and synapses.

Huang B, Liang F, Zhong L, Lin M, Yang J, Yan L, Xiao J, Xiao Z - Sci Rep (2015)

Best frequencies of recording sites.(a) 80 dB pure tone bursts at 5–26 kHz evoked AEPs from a recording site. (b) An amplificatory sample shown in a 17 kHz panel to demonstrate AEP waveforms and the extracted parameters, i.e., latency and amplitude. The AEP (red line) was average line for 10 samples (gray lines) to the same acoustic stimulus. (c) Definition of BF. (d) Summary of best frequencies of all recording sites in twenty-five mice.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526847&req=5

f1: Best frequencies of recording sites.(a) 80 dB pure tone bursts at 5–26 kHz evoked AEPs from a recording site. (b) An amplificatory sample shown in a 17 kHz panel to demonstrate AEP waveforms and the extracted parameters, i.e., latency and amplitude. The AEP (red line) was average line for 10 samples (gray lines) to the same acoustic stimulus. (c) Definition of BF. (d) Summary of best frequencies of all recording sites in twenty-five mice.
Mentions: To identify the BF of a recording site, pure tone bursts of various frequencies at 80 dB SPL were delivered to the mice. For example, the AEP recorded with an electrode penetrated at 816 μm depth in ICC of a mouse M20110525, tuned to 5–26 kHz pure tone bursts (Fig. 1a). At each frequency, ten AEP waveforms (Fig. 1a, the gray lines) were averaged (Fig. 1a, the red line). Each average AEP waveform had P0, N1 and P1 waves (Fig. 1b, the red line). The time from the beginning of the acoustic stimulus to the N1 peak was defined as latency, and the voltage difference from the N1 peak to the P1 peak was defined as amplitude (Fig. 1b). From 5 to 26 kHz, the amplitudes to 80 dB acoustic stimuli (A80) first increased to a vertex at 14 kHz, and then decreased gradually (Fig. 1c). The frequency with the largest A80 was defined as BF. The mice were sorted by BF of the recording site. Mouse M20110525 is No. 9 with BF 14 kHz. The best frequencies of recording sites of twenty-five mice were 6–26 kHz (Fig. 1d), which were distributed in different locations of ICC. To obtain AEP latency and amplitude to different acoustic intensities, auditory evoked potentials to seven different acoustic intensities (from 30 to 90 dB in 10 dB steps) at BF in each recording session were recorded.

Bottom Line: Auditory evoked potential (AEP) is an effective index for the effects of general anesthetics.However, it's unknown if AEP can differentiate the effects of general anesthetics on nerve fibers and synapses.Therefore, we conclude that, AEP latency is superior to amplitude for the effects of general anesthetics, ∆L monitors the effect of hypothermia on nerve fibers, and ∆I monitors a combined effect of anesthesia and hypothermia on synapses.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, PR China [2] Department of Anesthesiology, Nanfang Hospital, Southern Medical University, Guangzhou 510515, PR China.

ABSTRACT
Auditory evoked potential (AEP) is an effective index for the effects of general anesthetics. However, it's unknown if AEP can differentiate the effects of general anesthetics on nerve fibers and synapses. Presently, we investigated AEP latency and amplitude changes to different acoustic intensities during pentobarbital anesthesia. Latency more regularly changed than amplitude during anesthesia. AEP Latency monotonically decreased with acoustic intensity increase (i.e., latency-intensity curve) and could be fitted to an exponential decay equation, which showed two components, the theoretical minimum latency and stimulus-dependent delay. From the latency-intensity curves, the changes of these two components (∆L and ∆I) were extracted during anesthesia. ∆L and ∆I monitored the effect of pentobarbital on nerve fibers and synapses. Pentobarbital can induce anesthesia, and two side effects, hypoxemia and hypothermia. The hypoxemia was not related with ∆L and ∆I. However, ∆L was changed by the hypothermia, whereas ∆I was changed by the hypothermia and anesthesia. Therefore, we conclude that, AEP latency is superior to amplitude for the effects of general anesthetics, ∆L monitors the effect of hypothermia on nerve fibers, and ∆I monitors a combined effect of anesthesia and hypothermia on synapses. When eliminating the temperature factor, ∆I monitors the anesthesia effect on synapses.

No MeSH data available.


Related in: MedlinePlus