延髄循環調節中枢による交感神経自発放電の発生機構;人工脳脊髄液灌流標本による研究

抄録

A major source of excitatory drive to the pre-ganglionic sympathetic neurons originates from the rostral ventrolateral medulla (RVLM). RVLM sympathetic premotor neurons (RVLM neurons) have spontaneous activity in vivo. For the generation of RVLM neuron activity, "Network theory" and "Pacemaker theory" have been suggested by in vivo and in vitro studies. However, it is still unclear which one is right. We studied how RVLM sympathetic premotor neurons generate their activity using an in situ arterially perfused preparation (the working heart-brainstem preparation). We recorded activities of the thoracic sympathetic chain and RVLM neurons. The firing response of RVLM neurons during hypoxic-induced gasping is heterogeneous with some inhibited and others persisting. The finding that some RVLM neurons continue to fire after blockade of fast synaptic transmission is consistent with the hypothesis that they may have intrinsic pacemaker activity. Since some RVLM neurons remained responsive to hypoxia after blockade of fast excitatory and inhibitory synaptic transmission, they may be directly sensitive to hypoxia. Some RVLM neurons may be central oxygen sensors and exhibit pacemaker activity during hypoxia to ensure high levels of sympathetic activity and hence maintenance of arterial pressure. [J Physiol Sci. 2006;56 Suppl:S26]