抄録
Neurons in the rostral ventrolateral medulla (RVLM neurons) receive inputs from various sources, including baroreceptors, and then regulate activity of sympathetic preganglionic neurons. Though the RVLM neurons are assumed to mediate the viscero-sympathetic reflex, it has not been clarified yet. In the present study, we investigated the role of the RVLM neurons in the viscero-renal sympathetic reflex in anesthetized and vagotomized rabbits. Electrical stimulation of the greater splanchnic nerve (SPN) evoked reflex responses in the renal sympathetic nerve activity that were composed with inhibitory and/or excitatory components. Bilateral microinjection of muscimol, a GABA receptor agonist, into the RVLM, considerably blocked the reflex responses. Bilateral microinjection of bicuculline, a GABA receptor antagonist, attenuated largely inhibitory component, on the other hand, excitatory component was eliminated by kynurenic acid, the glutamate receptor antagonist. Activities of 21 RVLM neurons were recorded. Twenty neurons among them responded to the SPN stimulation. Responses of neurons also consisted of inhibitory and/or excitatory components. Excitatory component of these neurons preceded that of renal nerve activity by about 100 ms. This latency difference was almost same as that of the inhibitory responses evoked by the aortic nerve stimulation. In conclusion, the renal sympathetic reflex responses evoked by the SPN stimulation are mediated by the RVLM neurons, and GABA and glutamate are used as transmitters in this reflex at the RVLM. [J Physiol Sci. 2007;57 Suppl:S207]
