Effects Of Propofol And Ketamine On Middle Latency Auditory Evoked Potentials By Neurons In The Ventral Partition Of The Medial Geniculate Body In Rats And Its Possible Mechanisms

Part One The effects of propofol and ketamine on middle latency auditory evoked potentials by neurons in the ventral partition of the medial geniculate body in ratsObjective To investigate the effects of propofol and ketamine on middle latency auditory evoked potentials(MLAEP) by neurons in the ventral partition of the medial geniculate body(MGBv) in rats.Methods Seventy-two SD rats were divided into 4 groups randomly:propofol group(P group),ketamine group(K group),intralipid group(â… group),saline group (NS group).Propofol group included 5.6μmol/L(P1 group),16.8μmol/L(P2 group),56μmol/L(P3 group),168μmol/L(P4 group) and 560μmol/L(P5 group). Ketamine group(K group) included 18μmol/L(K1 group),54μmol/L(K2 group),180μmol/L(K3 group),540μmol/L(K4 group),1800μmol/L(KS group).With the method of micromedicine injection,injecting into MGBv in rats with 5.6μmol/L(P1 group),16.8μmol/L(P2 group),56μmol/L(P3 group),168μmol/L(P4 group),560μmol/L(P5 group) propofol,18μmol/L(K1 group),54μmol/L(K2 group),180μmol/L(K3 group),540μmol/L(K4 group),1800μmol/L(K5 group) ketamine,intralipid or saline 0.2μl.Auditory stimuli was delivered by earphone.The change of every wave on middle latency auditory evoked potentials by neurons in MGBv was recorded.Results 56μmol/L(P3 group),168μmol/L(P4 group),560μmol/L(P5 group) propofol all made obvious increased latency and decreased amplitude,especially in wave Na,Pa and Nb(P＜0.05).5.6μmol/L(P1 group),16.8μmol/L(P2 group)propofol and 18μmol/L(K1 group),54μmol/L(K2 group),180μmol/L(K3 group),540μmol/L(K4 group),1800μmol/L(K5 group) ketamine had no effect. Intralipid group(â… group) and saline group(NS group) had no effect.Conclusions 56μmol/L(P3 group),168μmol/L(P4 group),560μmol/L(P5 group) propofol inhibited MLAEP in MGBv in rats and had concentration dependence effects,but ketamine had not.Part Two The effects of propofol and ketamine on ion channels in the ventral partitionof the medial geniculate body in ratsObjective To investigate the effects of propofol and ketamine on ion channels in the ventral partition of the medial geniculate body(MGBv) in rats,and study their mechanisms.Methods 48 SD rats were divided into 8 groups randomly:Ni²⁺ plus propofol group(A1 group),Cd²⁺ plus propofol group(B1 group),4-AP plus propofol group (C1 group),TTX plus propofol group(D1 group),Ni²⁺ plus ketamine group(A2 group),Cd²⁺ plus ketamine group(B2 group),4-AP plus ketamine group(C2 group), TTX plus ketamine group(D2 group),With the method of micromedicine injection,injecting into the MGBv in rats with Ni²⁺,Cd²⁺,4-AP and TTX 0.2μl, observing the change of every wave of middle latency auditory evoked potentials (MLAEP) in the ventral partiotion of the medial geniculate body in rats.And then given the 56μmol propofol or 180μmol ketamine 0.2μl,observing the the change of every wave of MLAEP in the MGBv in rats.Results With Ni²⁺ or 4-AP,every wave of MLAEP(A1 or C1 group) in the MGBv in rats had no change.Then given propofol,amplitudes were decreased in wave Na-Pa and latency was increased in wave Na,Pa and Nb(p＜0.05).With Cdcl₂, latency(B1 group) was increased in wave Na,Pa and Nb(P＜0.05).Then given propofol,latency was unchanged in wave Na,Pa and Nb and amplitudes were decreased in wave Na-Pa(P＜0.05).With TTX,amplitudes(D1 group) were decreased in wave Na-Pa(P＜0.05).Then given propofol,amplitudes were unchanged in wave Na-Pa and latency was increased in wave Na,Pa and Nb(P＜0.05).With Ni²⁺ or 4-AP,every wave of MLAEP(A2 or C2 group) in the MGBv in rats had no change.Then given ketamine,every wave of MLAEP still had no change.With Cdcl₂,latency(B2 group) was increased in wave Na,Pa and Nb (P＜0.05).Then given ketamine,every wave of MLAEP had no change.With TTX, amplitudes(D2 group) were decreased in wave Na-Pa(P＜0.05).Then given ketamine,every wave of MLAEP had no change.Conclusions Propofol influnced MLAEP in the MGBv in rats by inhibting sodium and calcium channel.Amplitudes were decreased in wave Na-Pa in the MGBv in rats by inhibting sodium channel.Latency was unchanged in wave Na,Pa and Nb in the MGBv in rats by inhibting calcium channel.Part three The effects of propofol and ketamine on persistent sodium currents and high voltaged activated calcium currents by neurons in the ventral partition of the medial geniculate body in ratsObjective To testify the effects of propofol and ketamine on persistent sodium currents and high voltaged activated calcium currents by neurons in the ventral partition of the medial geniculate body(MGBv) in rats.Methods SD rats aged two or three weeks were divided into 4 groups randomly: propofol group,ketamine group,intralipid group and saline group.Propofol group included 5.6μmol/L,16.8μmol/L,56μmol/L,168μmol/L and 560μmol/L propofol.Ketamine group included 18μmol/L,54μmol/L,180μmol/L,540 mol/L and 1800μmol/L ketamine.With the whole-cell patch clamp recording method,observing and recording the effects of propofol and ketamine on persistent sodium currents and high voltaged activated calcium currents in the MGBv in rats.Results 16.8μmol,56μmol,168μmol,560μmol propofol and 1800μmol ketamine inhibited persistent sodium currents and currents.5.6μmol propofol,18μmol,54μmol,180μmol,540μmol ketamine,saline and intralipid had no effect.Conclusions Propofol inhibited the persistent sodium currents and high voltaged activated calcium currents by neurons in the MGBv in rats,and have concentration dependences effects.Ketamine only inhibited the persistent sodium currents and high voltaged activated calcium currents by neurons in the MGBv in rats with very high concentration.