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 metaboli tes were measured in brain, corpora cardiaca/corpora allata complex, t horacic ganglia and optic lobes from individual male cabbage looper mo ths, Trichoplusia ni, using HPLC with electrochemical detection. Measu rements were made from individuals in late photophase and compared wit h levels from individuals at mid-scotophase. Individuals at mid-scotop hase had been observed for locomotor activity throughout the dark peri od and then assayed in the sustained-flight tunnel with a low, thresho ld, dose of sex pheromone prior to dissection. Individuals were select ed for dissection if they exhibited a complete upwind flight to the ph eromone source, or if they did not respond at all. Mid-scotophase leve ls of octopamine in the brain and thoracic ganglia, dopamine in the th oracic ganglia, and 5-hydroxytryptamine in the brain and thoracic gang lia were all significantly lower than photophase levels. Scotophase le vels of octopamine in individuals that responded to a low dose of pher omone were significantly lower than levels from males that did not res pond. 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-sc otophase levels of amines and the degree of locomotor activity exhibit ed, but there was a strong correlation between decreased levels of oct opamine and dopamine in the thoracic ganglia and high levels of locomo tor 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-a cetyldopamine were significantly greater than photophase levels, sugge sting increased metabolism of this amine as well. Our results indicate that changes in amine levels within specific tissues can be correlate d 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.