Minoura Y, Onimaru H, Iigaya K, Homma I, Kobayashi Y
The electrophysiologic responses of sympathetic preganglionic neurons to angiotensin II and aldosterone. [JOURNAL ARTICLE]
Am J Physiol Regul Integr Comp Physiol 2009 Jun 24.
The intermediolateral cell column (IML) of the spinal cord is an important area where sympathetic impulses propagate to peripheral sympathetic organs. Angiotensin II (Ang II) and aldosterone are important components of the renin-angiotensin-aldosterone system (RAAS) which activate the sympathetic nervous system. Each is partly synthesized in the brain and plays a paracrine role in the regulation of blood pressure independently of RAAS in the periphery. Our purpose in the present study was to clarify the contributions of sympathetic preganglionic neurons in the IML (IML-neurons) and the effects of Ang II and aldosterone on the sympathetic nervous system. To examine responses to Ang II and aldosterone, we intracellularly recorded 104 IML-neurons using a whole-cell patch-clamp technique in spinal cord slice preparations. 1) IML-neurons were classified into two types: silent and firing. Both neuron types were significantly depolarized by Ang II, and candesartan inhibited this depolarization. 2) After pretreatment with tetrodotoxin (TTX), firing neurons (but not silent neurons) were significantly depolarized by Ang II. 3) Aldosterone significantly increased the number of excitatory postsynaptic potentials (EPSPs) in both neuron types, but this response disappeared after pretreatment with TTX. 4) Ang II and aldosterone had no synergistic effects on the IML-neurons. 5) The silent neurons had large cell soma, and many more dendrites than the firing neurons. These results suggest that Ang II acts pre/and post-synaptically in IML-neurons, while aldosterone acts mainly pre-synaptically. Thus, the physiological effects of these substances are likely to be transmitted via specific membrane receptors of IML and/or pre-synaptic neurons. Key words: sympathetic preganglionic neuron, intermediolateral cell column, angiotensin II, aldosterone.
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