PNMT-containing catecholaminergic neurons are not necessarily adrenergic.
The intermediolateral cell column (IML) in the spinal cord is densely innervated by the phenylethanolamine-N-methyltransferase (PNMT)-containing neurons of the ventrolateral medulla (C1 cell group). The present study used a sensitive HPLC-EC assay for catecholamines to quantitate epinephrine levels in the region of the spinal cord containing the IML. In dissections of thoracic cord enriched in IML, as well as total thoracic cord, epinephrine levels were below the limit of sensitivity of the assay, indicating that epinephrine levels were less than 0.2 pg/mg tissue. In the region of the IML, epinephrine levels were less than 0.05% of the norepinephrine content. Thus, no epinephrine could be detected in the IML even though the IML contains a dense network of nerve terminals that stain immunohistochemically for PNMT and the other enzymes required for epinephrine biosynthesis. These results suggest that nerve terminals that contain all the enzymes required for epinephrine biosynthesis are not necessarily adrenergic.
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Department of Behavioral Neuroscience, University of Pittsburgh, PA 15260.
D000320:Adrenergic Fibers / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004837:Epinephrine / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000145:classification / Q000201:enzymology*; D010625:Phenylethanolamine N-Methyltransferase / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000166:cytology* / Q000201:enzymology
D010625:Phenylethanolamine N-Methyltransferase; D004837:Epinephrine