| Objective:1.To investigate the effects of propofol on the discharge of inspiratory neurons in the brainstem slices from neonatal rats2.To study the mechanism of propofol on the discharge of inspiratory neurons in the brainstem slices from neonatal rats. Methods:Experiments were performed on in vitro brainstem slices from neonatal rats. Newborn SD rats (0-3days) of either sex were used. Respiratory rhythmical discharge activity of the hypoglossal nerve was recorded by suction electrode. Extracellular recordings were made from 42 neuronal units with respiratory-related rhythmical activity. The effects of propofol on the inspiratory neurons were recorded by adding these drugs into the perfused modified Kreb's solution (MKS). Forty two neuronal units were divided into 7 groups: group 1 : control group in which neuronal units were perfused with MKS only, group II ~ V: propofol groups in which neuronal units were perfused continuously for 3 min with different concentrations of propofol(5,20,50,100μmol/L). group VI: bicuculline-propofol group in which neuronal units were continuously perfused with a specific GABAA receptor blocker, bicuculline(Bic, 20nmol/L)and propofol(20umol/L). group VII: strychnine-propofol group in which neuronal units were continuously perfused with a specific Gly receptor blocker, strychnine(STR, 100μmol/L)and propofol(20μmol/L).The discharge time of inspiratory, expiratory, the peak value of inspiratory discharge and the frequency of respiration were recorded before and 1, 3, 5, 10, 15, 30min after propofol or bicuculline-propofol or strychnine-propofol perfusion. Results:1. In control group, there was no significant change in all parameters at the designated time internals.2. In group II ~IV, at Imin to 30min after propofol perfusion, the dischargetime significantly became shorter and at 5min, 4 out of 6 neuronal units were stopped in group V (propofol 100μmol/L). The inspiratory discharge time was inhibited in a concentration-dependent manner in 11 ~IV group. At 3min to 30min, the expiratory times become prolonged and frequency of respiration showed decrease.3. With the application of bicuculine(20μmol/L) and propofol(20μmol/L), the discharge time of inspiratory neurons and expiratory time did not change significantly after perfusion.4. With the application of strychnine(100μmol/L) and propofol(20μmol L). the discharge time of inspiratory neurons did not change significantly after perfusion and expiratory time still become prolonged significantly at 10min, 15min. 30min after perfusion.Conclusion:1. Propofol inhibits the discharge of inspiratory neurons in a concentration-dependent manner as shown by short of discharge time of inspiratory neurons and prolongation of the times of expiration.2. GABAA receptor may play an important 'role in inhibitory action of propofol on inspiratory neuron in the isolated brainstem slices from neonatal rats.3. Gly receptor may take part in the role in inhibitory action of propofol on the isolated brainstem slices from neonatal rats. |
