Study On Role Of Propofol On The Spontanous Rhythmical Respiratory Discharges In The Isolated Medulla-spinal Cord Preperation Of Mewborn Rats

Objects 1. To observe the effects of propofol on the spontanous rhythmical respiratory discharges (SRRD) in the isolated medulla-spinal cord preparation of newborn rats. 2. To investigate the possible mechanism of propofol on the basic respiratory center in the medulla of medulla-spinal cord preparation from newborn rats. 3. To study the possible region of the effects of propofol on the basic respiratory center using isolated medulla-spinal cord preparation of newborn rats. Methods The methods used in the present study were similar to that of Suzue抯 description to establish the modle of isolated medulla-spinal cord preparation from newborn rats. The one-way ANOVA analysis was applied to produce different experimental groups. Drugs were administrated by perfusion and local microinjection. The respiratory activities could be monitored by using suction electrodes to record the spontanous rhythmic respiratory discharges (SRRD) of the C4 or C5 ventral root. Results 1. Under normal perfusion conditions, the SRRDs were mainly regular .The average burst Freuency- amplitude and IAD(integral area of discharge ) of the SRRD were 6.57?.63 bursts/min 205.23?2.3O.tV and 46.85? 5.27kV*S respectively. 2. Propofol(5 to 250.Lmol/L) inhibited the SRRD in a concentration-dependent manner,but in the first 3 minutes SRRD shows a temporary xcitation?that Freuency increased and Te became shorter after applied propofol by perfused. In 5 minutes Ereuency begean to slow down and Te prolonged , and 7 of 8 cases SRRD were stoped in 1 Snin after Propofol perfused in group of 250 jimol/L (another were in 30mm) Ti had no significent change after applied propofol in all groups but Amp and lAD showed some degree enlarge Tonly in group of 250.mmol!L propofol both the Amp and lAD had significently decreased until SRRD stoped 3. Pretreatment with BIC(20.tmol/L) and then perfusion with propofol (2Opmol/L), SRRD had no significent changes. 4. The results of microinjection groups are: injection the modified Krebs solution MKS 0.25i.d/lateral, into bilateral mNRF , SRRD did not change significently . 0 injection into bilateral mNRE with different concentration Propofol(2050A00.200j.tmol/L ), SRRD shows concentration-dependent inhibition, that is Freuence reduce and Te dose-dependently prolong , but Freuency fasten and Te shorten only occurred in l00.tmol/L and 200kmmol/L propofol groups 1-3mm after propofol used ; No significent changs of Ti happened in all groups. Amp and lAD reduced in groups of 20. 50 and lOOj.tmol/L propofol in 5-10mm and recovered in follow ,but enhanced in 2001.tmol/L propofol group 1-3mm after propofol applied and reduced siginifcently in 10-30mm. 0 injection of S0ptmol/L Propofol into the bilateral candal nucleus ambignous(cNA) , as area control , made no significent changs in SRRD. ?injection of Propofol 50tmol/L after pretreatment with BIC 50i.tmol/L , SRRD had no significent changes. Conclusion: The present study shows that in the in vitro medulla-spinal cord preparation of neonatal rats: 1) propofol exerts actions on the spontanous respiratory rhythmical discharges(SRRD) with conecntration-dependent inhibition; 2) the action of propofol mainly mediated by GABAA receptor on inhibitory SRRD of the isolated medulla-spinal cord preparation from newborn rats, and indicated that GABAA receptor may be the primary target for this inhibitory action of propofol on basic respiratory cente...