Connection Changes in Somatosensory Cortex Induced by Different Doses of Propofol

Zhaoduan Li,Xingkui Liu,Jinshan Shi,Peng Xie,Tian Yu,Yu Zhang,Yi Zhang,Zhongcong Xie

doi:10.1371/journal.pone.0087829

Abstract

BackgroundThe mechanism by which general anesthetics, widely used in clinical practice for over 160 years, effects on sensory responsiveness has been unclear until now. In the present study, the authors sought to explore the effect of different doses of propofol on somatosensory cortex by whisker stimulation in rats.MethodsIn a fixed cage, rats were anesthetized with propofol 80 mg/kg intraperitoneally and then cathetered tail vein with 23-gauge metal needle connected with a pump. Two holes (2 mm diameter) were drilled and recording electrodes implantated in the primary somatosensory cortex barrel field (S1BF) and secondary somatosensory cortex (S2). The extracellular (20 rats) and intracellular (8 rats) recordings were used to test the neuron activity in both cortices at different doses of propofol (20, 40 and 80 mg/kg/h) through tail vein by pump. Meantime, vibrissal, olfactory, corneal responses (VOCR, sedation), and tail-pinch response (TRP, analgesia) were tested every 10 min during the doses of propofol 20, 40 and 80 mg/kg/h.ResultsVOCR and TRP were depressed by propofol in a dose-dependent manner. The amplitude by whisker stimulation in S1BF was stronger and the peak latency was shorter compared with that of in S2. The response latency of S1BF and S2 was increased by raising infusion rate of propofol with the response latency in S2 being longer than that in S1BF at the same doses of propofol. The cross-correlation between S1BF and S2 decreased as the propofol infusion rate increased. The input resistance was higher by increasing infusion rate of propofol.ConclusionThe sedation and analgesia effects of propofol were dose-dependent. Both the connectivity and instinctive oscillation between S1BF and S2 were proportionally modulated by the different doses of propofol.

Highlights

General anesthesia has been used in clinical practice for more than 160 years, but the neurophysiological mechanisms of unconsciousness, amnesia, analgesia and immobility are still unclear, especially for the mysterious unconsciousness
The neuron activities of S1BF and S2 were recorded simultaneously and for convenience, group A, group B and group C were named to compare the changes between different doses of propofol 20, 40, 80 mg/kg/h
When the rats were infused with propofol 20 mg/kg/h, all the responses except vibrissal remained the same

Summary

Introduction

General anesthesia has been used in clinical practice for more than 160 years, but the neurophysiological mechanisms of unconsciousness, amnesia, analgesia and immobility are still unclear, especially for the mysterious unconsciousness. Scientific evidence suggests that various agents affect different, welldescribed regions of the central nervous system by acting on different receptors and receptor subunits [1,2], leading to highly agent-specific effects. Such different targets may result in various clinical effects of different anesthetics. Some investigators concluded that particular anesthetic has an effect on the evoked response and it is important to consider the agent-specific mechanisms that drive general anesthesia [3,4]. The authors sought to explore the effect of different doses of propofol on somatosensory cortex by whisker stimulation in rats

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