Aim: To observe the effects of sustained electrical stimulation at Bötzinger complex (Böt. c) on phrenic nerve discharges.
Methods: Sustained electrical stimulation (10--50 microA, 40-100 Hz, 0.3 ms, for 15-30 s) of Böt. C on 30 urethane anaesthetized, vagotomized, paralyzed and artificially ventilated rabbits.
Results: Sustained electrical stimulation of Bot. C produced the inhibition or "inspiratory off-switch" of phrenic discharge during the stimulation. The inhibition of the phrenic discharges showed intensity and frequency dependence. Habituation was shown during the stimulation, showing the magnitude of the phrenic nerve discharge increased gradually. Post-stimulus rebound exhibited upon the cessation of the stimulation, showing the magnitude of the phrenic activity increased significantly. Short-term memory was shown in the habituation of the phrenic activity.
Conclusion: Non-associative learning is involved in the central control of respiratory modulation in the Böt. C and synaptic plasticity may exist in the respiratory neurons of Böt. C.