ABSTRACT
Objective To explore the modulation roles of gamma-aminobutyric acid A(GABAA) receptor on respiratory rhythmical discharge activity in brainstem slice of neonatal rats.Methods Experiments were performed on in vitro neonatal rats brainstem slices.The slices containing the medial region of the nucleus retrofacialis(mNRF)with the hypoglossal nerve rootlets retained was prepared in which the respira-tory-related rhythmic discharge activity(RRDA)were recorded from hypoglossal nerve rootlets by suction electrode.The possible role of GABAA receptor on RRDA was investigated by administration of GABA and its antagonist bicuculline in modified Kreb′s solution(MKS),for perfusion of the brainstem slices.Eighteen slices positive of RRDA were randomly divided into three equal groups:the first group of slices was perfused with different concentrations(10,20,40,60 ?mol/L) GABA and the most effective concentration was selected;the second group of slices was perfused with 10 ?mol/L bicuculline;the third group of slices was perfused with 10 ?mol/L bicuculline plus 40 ?mol/L GABA.The RRDA in 3 groups were observed.Results GABA decreased RRDA,40 ?mol/L was the most effective concentration.It shortened inspiratory time(TI),decreased integral amplitude(IA),prolonged respiratory cycle(RC) and expiratory time(TE) respectively.By contrast,10 ?mol/L bicuculline produced opposite effects on RRDA,it prolonged TI,increased IA,shortened RC and TE respectively.40 ?mol/L GABA plus 10 ?mol/L bicuculline had no significant effects on RRDA.Conclusion GABA plays an important role in modulate RRDA of neonatal rats via GABAA receptor.
ABSTRACT
Objective:To explore the role of reactive oxygen species(ROS,i.e,H_2O_2 and O_2-) in regulation of respiratory rhythm in the medial area of nucleus retrofacialis(mNRF).Methods: Medullary slices of neonatal SD rats,including hypoglossal nerve(Ⅻn) and mNRF,were made according to Suzue's method.Simultaneous recording of the Ⅻn respiratory rhythmic activity(RRA) with suction electrode and the respiratory neuronal discharge were performed with whole cell patch in the mNRF on the brainstem slice in vitro.The effect of t-butyl hydroperoxide(tBHP) and ?-lipoic acid(?-LA) on the respiratory pacemaker neurons and respiratory rhythm in the mNRF were observed.Results: tBHP significantly decreased respiratory cycle(RC) and increased respiratory amplitude;?-LA significantly increased RC and decreased its amplitude.Meanwhile,?-LA significantly prolonged the action potential of the respiratory cadmium-insensitive pacemaker neurons and reduced its amplitude,but it had no significant effect on the cadmium-sensitive respiratory pacemaker neurons.Voltage steps and ramps showed that ?-LA inhibited both the transient and persistent sodium current of cadmium-insensitive pacemaker neurons.Conclusion: ROS has an excitatory effect on the respiratory rhythm and the cadmium-insensitive respiratory pacemaker neurons through modulating sodium current.