title: 5,7-Dihydroxytryptamine identifies living dopaminergic neurons in mesencephalic cultures.
abstract: The autofluorescent serotonin analogue 5,7-dihydroxytryptamine (5,7-DHT) was used to identify living catecholaminergic neurons in monolayer cultures derived from the embryonic rat mesencephalon. A high correlation between 5,7-DHT accumulation and aldehyde-induced catecholamine fluorescence as well as tyrosine hydroxylase but not dopamine-beta-hydroxylase or phenylethanolamine-N-methyltransferase immunoreactivity was found. This indicates that these cells were dopamine-containing neurons. Whole-cell patch recordings showed that all mesencephalic neurons had resting membrane potentials of -50 mV or greater and input resistances ranging between 200 and 700 M omega and exhibited spontaneous action potentials and postsynaptic potentials. The duration of the action potential of the dopamine-containing neurons was characteristically longer than that of the non-dopamine-containing mesencephalic cells. In some dopamine-containing neurons, repolarization of the action potential was clearly biphasic, and the slow phase of repolarization was reversibly blocked by local application of Cd2+ or Co2+. This "shoulder" in the action potential was never observed in non-dopamine-containing neurons, where Cd2+ or Co2+ application was always without effect. It is concluded that 5,7-DHT can be used to identify living dopamine-containing neurons in dissociated mesencephalic cultures and these neurons express distinct electrical properties.
mesh_terms: D015116:5,7-Dihydroxytryptamine / Q000378:metabolism*; D000200:Action Potentials; D000818:Animals; D004102:Dihydroxytryptamines / Q000378:metabolism*; D004298:Dopamine; D006651:Histocytochemistry; D008636:Mesencephalon / Q000166:cytology*; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D009474:Neurons / Q000166:cytology*; D051381:Rats
chemical_list: D004102:Dihydroxytryptamines; D015116:5,7-Dihydroxytryptamine; D004298:Dopamine