Studies on biogenic amines and metabolites in nervous tissue and hemolymph of male cabbage looper moths—III. Fate of injected octopamine, 5-hydroxytryptamine and dopamine

Abstract

Adult male cabbage looper moths, Trichoplusia ni, were injected with two dosages of octopamine, or 5-hydroxytryptamine, or dopamine. The dosages were 1 and 10 μg, the latter a dosage that was previously shown to induce changes in nocturnal locomotor activity (5-hydroxytryptamine) and sensitivity to sex pheromone (octopamine). Injections were made into the hemolymph in the head capsule dorsal to the supraesophageal ganglion. Males were injected 1 hr prior to the onset of scotophase, and then brains + optic lobes, thoracic ganglia and hemolymph were analyzed at five time intervals over the following 6 hr. Levels of the three amines and their N-acetylated metabolites were quantified using HPLC with electrochemical detection. With the 1 μg dosage of the three amines, there was a significant increase in hemolymph values, but no changes in levels in the nervous system. With the 10 μg dosage, significant increases in each amine were found in the hemolymph, thoracic ganglia and brain + optic lobes. Levels of injected amines then rapidly decreased from hemolymph and nervous tissue. Within 2.5 hr following injections, levels of octopamine and dopamine in the brain + optic lobes and thoracic ganglia stabilized at twice the level in saline injected controls, 5-hydroxytryptamine levels were below control levels and hemolymph levels of each amine were not significantly different from controls. Decreases in amine levels were accompanied by significant increases in the N-acetylated form of each amine. In no instance did we observe a measurable peak for metabolites that would suggest the presence of MAO activity.