The Effects of Propofol on Neural Responses in the Mouse Primary Auditory Cortex.

Abstract

Two-photon laser-scanning microscopy allows for the monitoring of all brain neurons with single-cell and single-action potential accuracy. This study aimed to investigate the neural responses of the primary auditory cortex to sound stimuli in awake and propofol-anesthetized mice using 2-photon laser-scanning microscopy. Twelve healthy adult male C57BL/6 mice were used in the present study. In each mouse, the scalp was removed over the entire dorsal skull, and the right primary auditory cortex (A1) located. The test stimulus, used in the awake and propofol-induced anesthetic state, was a group of tones with a random combination of 3 sound intensities and 8 sound frequencies. The calcium indicator GCaMP6s was virally expressed in cortical neurons and neuronal activity was recorded using 2-photon imaging. Calcium responses to sound stimuli in two thirds of the neuronal population of the A1 layer were significantly inhibited by propofol anesthesia. In a single neuron, the calcium responses were also inhibited by propofol anesthesia. In the waking state, △F/F (where F is the time series of fluorescence intensity) of all single neurons was significantly higher than that in the propofol-induced anesthetic state (n=669, P<0.001). Finally, in one example session and averaged across different fields of views (n=6 sessions), the response events to sound stimuli were also inhibited by propofol anesthesia. Anesthetic doses of propofol inhibited calcium transients and neuronal activity in the primary auditory cortex of mice.