%0 Journal Article
%T Sympathetic-correlated c-Fos expression in the neonatal rat spinal cord in vitro
%A Chun-Kuei Su
%A Chiu-Ming Ho
%A Hsiao-Hui Kuo
%A Yu-Chuan Wen
%A Chok-Yung Chai
%J Journal of Biomedical Science
%D 2009
%I BioMed Central
%R 10.1186/1423-0127-16-44
%X Autonomous generation of tonic sympathetic activity is fundamental to normal visceral functions. The primary source for sympathetic tone generation is the brain stem [1-4]. However, in neonatal rats, three or fewer thoracic spinal cord segments contain sufficient neural elements for spontaneous generation of sympathetic nerve discharge (SND; [5]). In vitro studies have reported that some sympathetic preganglionic neurons (SPNs) are spontaneously active in the absence of extraspinal inputs [6-9]. These in vitro observations are consistent with the in vivo observations that, being deprived of supraspinal inputs, isolated spinal cords generate substantial amounts of SND in adult animals [10-14]. Although an isolated spinal cord could generate SND under certain pathophysiological conditions, the spinal neurons responsible for SND genesis were largely unknown.Findings obtained from the studies of neural elements involved in sympathetic regulation at the level of the spinal cord could provide clues to elucidate the anatomical substrates underlying spinal SND genesis. It was found that peripheral visceral afferents project to the gray matter of the spinal cord at both superficial (lamina I and II) and deep layers (laminae V, VII, and X) [15-17], wherein sympathetic interneurons are concentrated in the deeper layers [18-20] and scattered in more dorsal laminae [21,22]. Moreover, a group of GABAergic sympathetic interneurons is located in the central gray matter or lamina X [23]. All these studies suggest that sympathetic-correlated neurons are mainly distributed in medial dorsal parts of the spinal cord.Using a reduced preparation that only retained splanchnic sympathetic nerve-thoracic spinal cord, we demonstrated that one prerequisite condition for in vitro SND genesis is to incubate the spinal cord at an ambient temperature ¡Ý 20¡ãC [24]. The optimal temperature for the cord to generate SND in the splanchnic nerves is 24.5 ¡À 1¡ãC [5,24]. However, because activities of diffe
%U http://www.jbiomedsci.com/content/16/1/44