title: Selective depletion of dopamine, octopamine, and 5-hydroxytryptamine in the nervous tissue of the cockroach (Periplaneta americana).
abstract: High-performance liquid chromatography with electrochemical detection was used to measure the concentrations of 3,4-dihydroxyphenylethylamine (dopamine), 5-hydroxytryptamine (5-HT), p-hydroxyphenylethanolamine (octopamine), alpha-methyl-p-tyrosine, and tryptophan in the cerebral ganglia of cockroaches (Periplaneta americana) after peripheral administration of alpha-methyl-p-tyrosine and alpha-methyltryptophan. In addition, the levels of dopamine, 5-HT, octopamine, alpha-methyl-p-tyrosine, and tryptophan were determined after injection of alpha-methyl-p-tyrosine, 6-hydroxydopamine, or 5,7-dihydroxytryptamine directly into the cerebral ganglia by means of microinjection needles. Peripheral administration of alpha-methyl-p-tyrosine (400-1,600 micrograms/insect) caused a reduction in dopamine and 5-HT concentrations in cockroach cerebral ganglia, although the reduction in dopamine concentrations was more pronounced. Peripheral injections of alpha-methyl-p-tyrosine also reduced octopamine levels in the cerebral ganglia. Peripheral injection of alpha-methyltryptophan (400-1,600 micrograms/insect) caused a marked reduction in 5-HT and tryptophan concentrations in cockroach cerebral ganglia without altering dopamine or octopamine concentrations. Central injections of alpha-methyl-p-tyrosine (80 micrograms/insect) reduced dopamine concentrations in the cerebral ganglia. However, neither 6-hydroxydopamine (20 micrograms/insect) nor 5,7-dihydroxytryptamine (20 micrograms/insect) caused reductions in amine levels when applied near or directly into the cerebral ganglia. The results suggest that specific lesions of aminergic neurons in insects by either 6-hydroxydopamine or 5,7-dihydroxytryptamine are impractical. The specific, long-lasting depletion of 5-HT by alpha-methyltryptophan suggests that this chemical may be useful in elucidating the functions of 5-HT in insects.
mesh_terms: D015116:5,7-Dihydroxytryptamine / Q000378:metabolism; D000818:Animals; D003058:Cockroaches / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D008297:Male; D008781:Methyltyrosines / Q000378:metabolism; D009420:Nervous System / Q000378:metabolism*; D009655:Octopamine / Q000378:metabolism*; D010526:Periplaneta / Q000378:metabolism*; D012016:Reference Values; D012701:Serotonin / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism; D019805:alpha-Methyltyrosine
chemical_list: D008781:Methyltyrosines; D009655:Octopamine; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D019805:alpha-Methyltyrosine; D014364:Tryptophan; C028435:2-octopamine; D004298:Dopamine