The effect of propofol on the spontanous rhythmical respiratory discharges in the isolated medulla-spinal cord preparation of newborn rats / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effects of propofol on the spontanous rhythmical respiratory discharges (SRRDs) in the isolated medulla spinal cord preparation of newborn rats and its possible mechanism Methods Newborn SD rats (0 3 days) of either sex were used Isolated medulla spinal cord preparation was made according to the method of Suzue, et al Brain stem was severed between medulla and pons and spinal cord was severed between cervical and thoracic segments Efforts were made to keep the ventral root of the cervical spinal nerves of possible, while the medulla spinal cord preparation was being removed The medulla spinal cord preparation was placed with the ventral side facing up in the bath continuously perfused with modified Krebs solution (MKS)(3 4ml/min,T=27℃, pH=7 3 7 4, 95% O 2 5% CO 2) glass adsorb electrodes containing Ag AgCl needle were attached to the rentral root of C 4 or C 5 spinal nerve SRRD were recorded, Forty eitht isolated medulla spinal cord preparations were divided into 7 groups: groupⅠ: control group in which preparation was perfused with MKS only; groupⅡ Ⅳ: propofol groups in which preparation was perfused continuously for 3 min with different concentrations of propofol (5, 20, 50, 100, 250 ?mol/L); group Ⅶ: bicuculine propofol group in which preparation was continuously perfuse for 3min with a specific GABAA receptor blocker, bicuculine (20?mol/L) followed by perfusion of propofol(20?mol/L) for another 3 min SRRDs were recorded before and 1, 3, 5, 10, 15, and 30 min after propofol or bicuculine propofol perfusion Results 1) In control group, there was no significant change in SRRDs at the designated time internals 2) In group Ⅱ Ⅵ after propofol perfusion, the bursts of SRRDs were inhibited in a concentration dependent manner, but at 1 3 min SRRD showed a temporary excitation (frequency increased and expiratory time became shorter), at 5 min frequency began to slow down and expiratory time became prolonged, at 15 min in 7 out of preparations were stopped in group Ⅵ (propofol 250 ?mol/L) Inspiratory time did not change significantly after propofol in all propofol groups, but integral area of discharge (IAD) of SRRD showed some enlargement until SRRDs stopped 3) with bicuculine(20 ?mol/L) pretreatment, SRRDs did not change significantly after perfusion with propofol (20 ?mol/L) Conclusions Propofol inhibits SRRDs in a conecntration dependent manner as shown by prolongation of expiratory time GABAA receptor may play an important role in inhibitory action of propofol on the isolated medulla spinal cord preparation from newborn rats