Quantification of periviscerokinin-1 in the nervous system of the Americancockroach, Periplaneta americana: An insect neuropeptide with unusual distribution

This study was undertaken to reveal the quantitative distribution of the in sect neuropeptide periviscerokinin-1 (Pea-PVK-1) in the central nervous sys tem of Periplaneta americana and to demonstrate that neurons stained in a p revious immunohistochemical study contain authentic Pea-PVK-1. For this, we combined ELISA, HPLC, and MALDI-TOF mass spectrometry. The high specificit y of the used antiserum enabled the quantification of Pea-PVK-1 in unsepara ted tissue extracts. No crossreactivities with other insect neuropeptides w ere detected in ELISA. Only two immunoreactive fractions, coeluting with sy nthetic Pea-PVK-1 in its oxidized and nonoxidized form, were found in HPLC- separated extracts of the brain, suboesophageal ganglion, metathoracic gang lion, second abdominal ganglion with or without perisympathetic organ, and terminal ganglion. By using MALDI-TOF mass spectrometry, we were able to co nfirm the existence of authentic Pea-PVK-1 in these fractions. The abdomina l perisympathetic organs contained 6.3 pmol Pea-PVK-1 per animal; another 1 .3 pmol were found in the abdominal ganglia. More than 90% of the total 8.2 pmol in the central nervous system was found in the abdominal ganglia and their perisympathetic organs. The corpora cardiaca and corpora allata did n ot contain immunoreactive material, suggesting that Pea-PVK-1 is not releas ed by the cephalic neurohaemal system. The quantitative distribution of Pea -PVK-1 differs considerably from that of other known insect neuropeptides, Arch. Insect Biochem. Physiol. 40:203-211, 1999. (C) 1999 Wiley-Liss, Inc.