title: Dopamine and norepinephrine in the gastrointestinal tract of mice and the effects of neurotoxins.
abstract: Evidence is lacking for neurons containing dopamine and acting as a neurotransmitter in the gastrointestinal tract. The relative percentage of dopamine to norepinephrine in noradrenergically innervated tissues (e.g., spleen) is known to be relatively constant within a species, and an increased percentage in any given tissue supports the premise that dopaminergic cells are present. We measured levels of norepinephrine, dopamine and the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) from segments of the gastrointestinal tract of mice after injection of: 1) saline (control); 2) 6-hydroxydopamine (6-OHDA); or 3) 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. In control tissues the ratio of dopamine/norepinephrine was higher (P less than .001) than in the spleen; DOPAC was present and the DOPAC/dopamine ratios were similar to those in the central nervous system (where dopaminergic neurons are present). Dopamine and norepinephrine were decreased by 6-OHDA in most myenteric plexus/smooth muscle tissues compared with controls and DOPAC was unmeasurable in most samples after 6-OHDA. In contrast, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine decreased norepinephrine but not dopamine in the smooth muscle/myenteric plexus. High dopamine/norepinephrine percentages, 6-OHDA depletion of dopamine and presence of DOPAC together suggest the presence of dopamine-containing neurons in the myenteric plexus of the gastrointestinal tract of mice.
mesh_terms: D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D004064:Digestive System / Q000032:analysis* / Q000187:drug effects; D004298:Dopamine / Q000032:analysis*; D006892:Hydroxydopamines / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000032:analysis; D008297:Male; D051379:Mice; D009197:Myenteric Plexus / Q000032:analysis; D009498:Neurotoxins / Q000494:pharmacology*; D009638:Norepinephrine / Q000032:analysis*; D016627:Oxidopamine; D011725:Pyridines / Q000494:pharmacology
chemical_list: D006892:Hydroxydopamines; D009498:Neurotoxins; D011725:Pyridines; D015102:3,4-Dihydroxyphenylacetic Acid; D016627:Oxidopamine; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D004298:Dopamine; D009638:Norepinephrine