[Effect of propofol on the electric discharge of inspiratory neurons in the brainstem of neonatal rats].

Objective: To investigate the effects of propofol on the electric discharge of the inspiratory neurons in the neonatal rat brainstem slices and its possible mechanism.

Methods: Experiments were performed on in vitro neonatal rat (of either sex, 0 to 30 d old) brainstem slices perfused with modified Kreb's solution (MKS), and the rhythmical discharge activity of the inspiratory neurons in the hypoglossal nerve was recorded by suction electrode. Thirty-six slices positive of respiratory-related rhythmic activity were randomly divided into 6 equal groups consisting of a control group (group I) with MKS perfusion, 4 propofol groups (groups II to V) with propofol treatment delivered via continuous MKS perfusion for 3 min at the doses of 5, 20, 50, 100 micromol/L respectively, and a bicuculline-propofol group (group VI) with the continuous perfusion of bicuculline (20 micromol/L) and propofol (20 micromol/L). The discharge time course of inspiratory, expiratory, peak inspiratory discharge and the frequency of respiration were recorded before and 1, 3, 5, 10, 15, 30 min after propofol or bicuculline-propofol perfusion.

Results: In control group, no significant changes took place in all Hreparameters in the whole course of the experiment. In groups II to IV, the discharge time was significantly reduced after propofol perfusion and at 5 min, and the discharge was arrested in 4 out of the 6 slices in group V, showing a concentration-dependent inhibition of the inspiratory discharge time by propofol. In contrast, the expiratory time course was prolonged and frequency of respiration decreased in the period of 3 to 30 min after propofol perfusion. Combined treatment of bicuculine and propofol produced no significant changes in the discharge time and expiratory time courses of the inspiratory neurons.

Conclusion: Propofol inhibits the discharge of inspiratory neurons in a concentration-dependent manner and GABA A receptor may play an important role in this process.