STUDIES ON BIOGENIC-AMINES AND THEIR METABOLITES IN NERVOUS-TISSUE AND HEMOLYMPH OF MALE CABBAGE-LOOPER MOTHS .2. PHOTOPERIOD CHANGES RELATIVE TO RANDOM LOCOMOTOR-ACTIVITY AND PHEROMONE-RESPONSE THRESHOLDS

Levels of octopamine, 5-hydroxytryptamine, dopamine and their metabolites were measured in brain, corpora cardiaca/corpora allata complex, thoracic ganglia and optic lobes from individual male cabbage looper moths, Trichoplusia ni, using HPLC with electrochemical detection. Measurements were made from individuals in late photophase and compared with levels from individuals at mid-scotophase. Individuals at mid-scotophase had been observed for locomotor activity throughout the dark period and then assayed in the sustained-flight tunnel with a low, threshold, dose of sex pheromone prior to dissection. Individuals were selected for dissection if they exhibited a complete upwind flight to the pheromone source, or if they did not respond at all. Mid-scotophase levels of octopamine in the brain and thoracic ganglia, dopamine in the thoracic ganglia, and 5-hydroxytryptamine in the brain and thoracic ganglia were all significantly lower than photophase levels. Scotophase levels of octopamine in individuals that responded to a low dose of pheromone were significantly lower than levels from males that did not respond. Levels of random locomotor activity over the scotophase were not correlated with the probability of a male responding to the threshold dose of pheromone. There also was no correlation between brain mid-scotophase levels of amines and the degree of locomotor activity exhibited, but there was a strong correlation between decreased levels of octopamine and dopamine in the thoracic ganglia and high levels of locomotor activity. Decreased levels of octopamine in the brain and thoracic ganglia over the dark period were correlated with increased levels of N-acetyloctopamine, suggesting that utilization of the amines occurs within the tissues over this time period. Mid-scotophase levels of N-acetyldopamine were significantly greater than photophase levels, suggesting increased metabolism of this amine as well. Our results indicate that changes in amine levels within specific tissues can be correlated with behaviors exhibited by individual insects. The results support the hypothesis that octopamine, dopamine and 5-hydroxytryptamine exert modulatory or transmitter roles in the central nervous system of the cabbage looper moth.