Sympathetic-correlated c-Fos expression in the neonatal rat spinal cord in vitro.
An isolated thoracic spinal cord of the neonatal rat in vitro spontaneously generates sympathetic nerve discharge (SND) at ~25 degrees C, but it fails in SND genesis at < or = 10 degrees C. Basal levels of the c-Fos expression in the spinal cords incubated at < or = 10 degrees C and ~25 degrees C were compared to determine the anatomical substrates that might participate in SND genesis. Cells that exhibited c-Fos immunoreactivity were virtually absent in the spinal cords incubated at < or = 10 degrees C. However, in the spinal cords incubated at ~25 degrees C, c-Fos-positive cells were found in the dorsal laminae, the white matter, lamina X, and the intermediolateral cell column (IML). Cell identities were verified by double labeling of c-Fos with neuron-specific nuclear protein (NeuN), glial fibrillary acidic protein (GFAP), or choline acetyltransferase (ChAT). The c-Fos-positive cells distributed in the white matter and lamina X were NeuN-negative or GFAP-positive and were glial cells. Endogenously active neurons showing c-Fos and NeuN double labeling were scattered in the dorsal laminae and concentrated in the IML. Double labeling of c-Fos and ChAT confirmed the presence of active sympathetic preganglionic neurons (SPNs) in the IML. Suppression of SND genesis by tetrodotoxin (TTX) or mecamylamine (MECA, nicotinic receptor blocker) almost abolished c-Fos expression in dorsal laminae, but only mildly affected c-Fos expression in the SPNs. Therefore, c-Fos expression in some SPNs does not require synaptic activation. Our results suggest that spinal SND genesis is initiated from some spontaneously active SPNs, which are capable of TTX- or MECA-resistant c-Fos expression.
Su
Chun-Kuei
CK
Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan. csu@ibms.sinica.edu.tw
Ho
Chiu-Ming
CM
Kuo
Hsiao-Hui
HH
Wen
Yu-Chuan
YC
Chai
Chok-Yung
CY
D000818:Animals; D000831:Animals, Newborn; D006651:Histocytochemistry; D008464:Mecamylamine / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000502:physiology*; D013696:Temperature; D013779:Tetrodotoxin / Q000494:pharmacology
D016760:Proto-Oncogene Proteins c-fos; D011978:Receptors, Nicotinic; D013779:Tetrodotoxin; D008464:Mecamylamine