The Effect Of Different Infusion Rate Of Propofol On S1 And S2 Somatosensory Cortex By Whisker Stimulation

Objective To observe the effect of different infusion rate of propofol on S1 and S2 somatosensory cortex by whisker stimulation and explore the general anesthesia mechanismMethods Seven Sprague Dawley rats (250--300 g) from Institution of Neron,Chinese Academy of Science were anaimals. Each animal was anesthetized with propofol 80mg/kg i.p.Until the rats losed righting reflex,we cathetered tail vein with 23-gauge metal needle and infused 20,40,80mg·kg-1·h-1 with pump respectively and devided into three groups accoding the infusion rate,each group was 7 cases. The rats were placed in a stereotaxic frame and we simutaneous recorded the brain activity in primary somatasensory and secondary somatosensory cortex by wisker stimulation. Each propofol infusion rate was recorded 40 min(for 20min spontaneous state and 20min whisker stimulation),then changed into initial infusion rate 10 min for balance,at last infused with the next dosage. The methode has described partly before but nobody simutaneously recorded the two somatosensory cortex by electrophysiology. We graded the sedation and analgesia effect of propofol and compared the difference of the both cortex brain activity and the somatosensory evoked potentials (SEP).Statistical Analysis As customary for the analysis of electroencephalographic data,7 all-band power and SEP parameters data in each experiment were using the means and SDs at the propofol infusion rate. The Bonferroni comparison was used to test for a significant difference in observations at different anesthesia depth from 20,40 to 80mg·kg-1·h-1. For the Bonferroni test, p<0.05 was accepted for statistical significance.Results 1) Sedation and analgeisa of propofol Compared with light anesthsia group(20 mg·kg-1·h-1),VOCR and TRP scores were reducing at the dosage of 40mg·kg-1·h-1 group and 80 mg·kg-1·h-1 group, the differenct had statistical significance,p<0.05.2) ERP The amplitude by whisker stimulation in S1 was stronger and the peak latency was shorter compared with S2;compared with the light anesthsia(20 mg·kg-1·h-1), theywave increased obviously at the dosage of 80 mg·kg-1·h-1,p< 0.05;in the same anesthesia depth,theθwave in S2 was more powerful than S1, p<0.05;the response latency of S1 caused by whisker stimulation was shorter than that in S2, p<0.05; Compared with the light anesthsia(20 mg·kg-1·h-1),the response latency of S1 in deep anesthesia80 mg·kg-1·h-1) was longer,and the differencce had statistical significance,p<0.05.3) The connectivity between S1 and S2 The neuronal activity cross-correlation between S1 and S2 was decreasing as we increased the dosage of propofol. Compared with the light anesthsia(20 mg·kg-1·h-1), the spontaneous neuronal activity cross-correlation beween S1 and S2 was descending at the dosage of 40 mg·kg-1·h-1 and 80 mg·kg-1·h-1,p< 0.05;while for the stimulation level,the neronal activity cross-correlation in 80 mg·kg-1·h-1 was descending than 20 mg·kg-1·h-1,and the differencce had statistical significance,p<0.05.Conclusion 1.The sedation and analgesia effect of propofol was stronger as increasing the dose.2 Propofol affected the different part of somatosensory cortex differently and the ERP response latency of S1 and S2 was longer as increasing propofol infusion rate.3 The different dosage of propofol affect not only the neron oscillation of somatosensory cortex but also dose-dependently affect the cross-correlation between S1 and S2.