QUANTITATIVE-DETERMINATION OF MYOTROPIC NEUROPEPTIDE IN THE NERVOUS-SYSTEM OF THE COCKROACH LEUCOPHAEA-MADERAE - DISTRIBUTION AND RELEASE OF LEUCOKININS

Being interested in the distribution and function of insect myotropic peptides, we developed a sensitive radioimmunoassay (RIA) using an ant iserum directed against the cockroach neuropeptide leucokinin 1. The l evels of leucokinin immunoreactivity were measured in extracts of diff erent portions of the nervous system, in the retrocerebral complex and in the hemolymph of the cockroach Leucophaea maderae. The brain conta ins about 1.9 pmol of immunoreactive material while the ganglia of the ventral nerve cord each contain less than 10% of this amount. Large a mounts of leucokinin immunoreactivity (6.6 pmol per tissue) were found in the corpora cardiaca-corpora allata (CC-CA) complex and in the hem olymph the titer was in the nanomolar range. When levels of leucokinin s were compared in male and female cockroaches, no differences could b e detected in any of the sample tissues. A calcium-dependent release o f leucokinin-immunoreactive material could be induced from isolated CC -CA complexes by high-potassium depolarization. The amount of released immunoreactivity, as measured in the bathing saline by RIA, was about 2% of the extractable leucokinin immunoreactivity in the CC-CA comple x. In Leucophaea maderae, the leucokinins apparently act both as neuro active substances in the central nervous system and as neurohormones r eleased into the circulation.