ABSTRACT
Objective To analyze the activities of cultured neuronal network in response to electric pulses stimuli with different intervals. Method Pairs of electric pulses with different intervals were added to rat hippocampal neurons cultured on multi-electrode arrays (MEA) substrate. Result The second response duration of the network increased with the decrease of the interval between two pulses. It was typical that the second duration after pulses with 10 ms interval increased greatly and it could be divided into two stages, i.e. quick response (within 10 ms) and slow response (near or beyond 100 ms). However, following pulses with 100 ms interval,there is practically no relation between the two responses; the second response duration was shorter and the number of spikes was fewer and their amplitudes were lower, which is similar to the result of single electric pulse stimulus. Conclusion The activity of cultured neuronal network was different in response to different electric stimulation patterns. Compared with spontaneous firing, the activity of the network is potentiated or depressed respectively after different stimulations.
ABSTRACT
OBJECTIVE: In general, it is known that repetitive regular stimuli induce tolerance and repetitive irregular stimuli induce sensitization. We sought to determine the dopamine response in the rat prefrontal cortex under the repetitive regular and repetitive irregular stimuli. METHODS: After giving irregular and regular electrical stimuli repetitively to rats, we measured the dopamine levels of prefrontal cortex. We compared these results with the dopamine levels of prefrontal cortex of rats which were given just one electrical stimulus. Samples were obtained using in vivo brain microdialysis. Dopamine levels in the samples were measured by high pressure liquid chromatography with electrochemical detection. RESULTS: 1) Dopamine levels of prefrontal cortex of both repetitive regular stimuli group and repetitive irregular stimuli group increased after electrical stimuli. 2) Dopamine levels of prefrontal cortex also significantly increased after just one electrical stimulus. 3) Among the repetitive regular stimuli group, repetitive irregular stimuli group and one stimulus group, the dopamine response was most significant in the repetitive irregular stimuli group. CONCLUSIONS: Repetitive irregular electrical stimuli induce sensitization of prefrontal cortex and repetitive regular electrical stimuli don't induce tolerance of prefrontal cortex.
Subject(s)
Animals , Rats , Brain , Chromatography, Liquid , Dopamine , Microdialysis , Prefrontal CortexABSTRACT
Objective To investigate the pharmacodynamic interactions between remifentanil and sevoflurane during general anesthesia for laparoscopic operation.Methods Sixty-five ASA I patients undergoing selective laparoscopic operations at the Department of Gynecology and the Department of General Surgery in People's Hospital were enrolled in this study.Sevoflurane was used for anesthesia induction with its expired concentration being kept stable,and different dosages of remifentanil(0,1,2,4,6,and 8 ng/ml)being added during the operation.When the expired concentration of sevoflurane reached an expected level(pseuto-state),the block somatic and cardiovascular responses to electrical tetanus stimuli(ETS;100 Hz,60 mA,5 s)were measured.The data were analyzed using NONMEM software to establish concentration-effect curves.Logistic regression was used to calculate the minimal alveolar concentration of sevoflurane under ETS(MACETS).Results In the cases received sevoflurane only,the somatic response was inhibited when MACETS reached 1.52%;while the cardiovascular response was inhibited when MACETS reached 2.24%.The MACETS was decreased significantly by adding low-dosage remifentanil.When the target-controlled concentration of remifentanil was 8 ng/ml,the MACETS for the inhibition of somatic and cardiovascular responses decreased by 70.0% and 76.3%,respectively.Conclusions There is a synergic effect between remifentanil and sevoflurane on the suppression of somatic and cardiovascular responses to ETS.Remifentanil produces a dose-dependent decrease of MACETS of sevoflurane.The effect is especially strong in low-dosage remifentanil group,but shows ceiling effect characteristics.