N-Acetyl 5-Hydroxytryptamine and N-Acetyl Dopamine in the Cockroach (Periplaneta americana)

Abstract

N-acetyl 5-hydroxytryptamine (NA-5-HT) and N-acetyl dopamine appear to be the major metabolites of 5-hydroxytryptamine (5-HT) and dopamine (DA) in insects. N-acetylated amines are produced by a number of insect tissues including nervous tissue (Murdock and Omar, 1981; Sloley and Downer, 1984) and malpighian tubules (Sloley, 1985). In addition DA derivatives including dopamine-3-0-sulphate, β-alanyl dopamine and NADA are involved in the tanning of insect cuticle (Morgan et al., 1987; Sloley and Downer, 1987). N-acetyl transferase is the enzyme used for the metabolism of amines in the adult insect while monoamine oxidase activity is almost totally absent. However, when insects ecdyse the large amount of DA eventually required for cuticular tanning is stored or transported as dopamine-3-0-sulphate (Sloley and Downer, 1987) and NADA phosphate (Bodnaryk et al., 1974). These reserves are rapidly converted to NADA, β-alanyl dopamine and possibly other compounds which are then incorporated into the cuticle.