Monoamine oxidase in the intermediolateral nucleus of the thoracic spinal cord of the rat. A histochemical study.
We examined monoamine oxidase (MAO) activity in the intermediolateral nucleus (IML) of the rat thoracic spinal cord by histochemistry with tyramine as a common substrate for both MAO types A and B. Light microscopy showed MAO activity in neuronal cell bodies, processes, and varicosities. Electron microscopic examination showed both MAO-positive and -negative neuronal cell bodies. In the stained cell bodies, histochemical reaction products were localized in the cytoplasm showing a selective association with mitochondrial outer membranes. MAO-positive axon terminals were often found in contact with MAO-negative neurons but only occasionally with MAO-positive neurons. MAO histochemistry in the IML was also performed using serotonin (a MAO type A preferential substrate) and beta-phenylethylamine (a MAO type B preferential substrate). Light microscopy identified MAO activity for serotonin in a plexus of varicosities but not in any neuronal cell bodies. The activity for beta-phenylethylamine was detected frequently in neuronal cell bodies but rarely in varicosities. Our findings indicate that two groups of IML neurons can be chemically distinguished, one contains MAO type B while the other lacks both MAO types A and B. In addition, many axon terminals contain MAO type A but only a few fibers include MAO type B in the IML.
Yamada
H
H
Department of Anatomy, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan.
Hida
T
T
Arai
R
R
D000320:Adrenergic Fibers / Q000737:chemistry / Q000201:enzymology / Q000648:ultrastructure; D000818:Animals; D006651:Histocytochemistry; D008297:Male; D008854:Microscopy, Electron; D008995:Monoamine Oxidase / Q000032:analysis / Q000378:metabolism*; D009638:Norepinephrine / Q000502:physiology; D010300:Parkinson Disease / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000502:physiology; D013116:Spinal Cord / Q000737:chemistry / Q000201:enzymology*
D012701:Serotonin; D008995:Monoamine Oxidase; D009638:Norepinephrine