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Persistence and effects of α‐methyl‐substituted amino acids on 5‐hydroxytryptamine and dopamine concentrations in cockroach ( Periplaneta americana ) nervous tissue
Author(s) -
Sloley B. Duff
Publication year - 1989
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.940100207
Subject(s) - periplaneta , nervous tissue , biology , cockroach , dopamine , endocrinology , nervous system , medicine , biogenic amine , tryptophan , serotonin , central nervous system , tyrosine , biochemistry , neurotransmitter , amino acid , ecology , receptor , neuroscience
The α‐methylated derivatives of tryptophan, tyrosine, and dihydroxyphenylalanine were injected into cockroaches ( Periplaneta americana ). The levels of these compounds and those of dopamine, 5‐hydroxytryptamine, tyrosine, and tryptophan in the nervous tissue, hemolymph, and fat body were measured at various times after drug administration. Levels of 5‐hydroxytryptamine and tryptophan in the nervous tissue are significantly reduced by α‐methyltryptophan administration. Concentrations of dopamine in nervous tissue are reduced by α‐methyltyrosine administration. This effect also persists for several weeks, and α‐methyltyrosine is observed in the nervous tissue 3 weeks after injection. Levels of dopamine and 5‐hydroxytryptamine in the nervous tissue are unaffected by α‐methyldihydroxyphenylalanine, and this compound is less persistent in nervous tissue than α‐methyltyrosine or α‐methyltryptophan demonstrates that these compounds can be absorbed and affect amine levels in the nervous tissue when included in the diet. Inhibition of tryptophan hydroxylation by crude enzyme preparations of cockroach nervous tissue was demonstrated with both α‐methyltryptophan and α‐methyltyrosine, with α‐methyltryptophan being the more effective inhibitor. Aromatic amino acid decarboxylase activity toward dihydroxyphenylalanine in crude enzyme preparations of cockroach nervous tissue was strongly inhibited by α‐methyldihydroxyphenylalanine and monofluoromethyldihydroxyphenylalanine, slightly inhibited by α‐methyltyrosine and unaffected by α‐methyltryptophan at concentrations up to 10 −3 M. The results indicate that α‐methyltyrosine and α‐methyltryptophan, but not α‐methyldihydroxyphenylalanine, can selectively alter amine concentrations in insect nervous tissue and that insects are only poorly able to metabolize or excrete these compounds. The selective and long‐lasting depletion of dopamine or 5‐hydroxytryptamine by some of these compounds suggest that they may be useful in behavioral studies designed to elucidate the roles of these amines in insects.