Storage and release of neuropeptides from the corpus cardiacum of the Eastern lubber grasshopper,Romalea microptera

✍ Scribed by Spring, Jeffrey H. ;Gäde, Gerd

• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 1008 KB
• Volume: 258
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402580107

✦ Synopsis

Abstract

In this study, we describe a method for the separation of AKH/RPCH‐family peptides using isocratic high performance liquid chromatography (HPLC). This improved method is simple, rapid, and sensitive and bypasses many of the difficulties associated with gradient HPLC. We have previously shown that the lubber grasshopper, Romalea, accumulates large quantities of the native peptides Ro I and Ro II (Spring and Gäde, __Journal of Experimental Zoology 241:__41–50, 1987). In the present study, we used isocratic HPLC to follow the changes in the amount of Ro I and Ro II during development. Overall the amount of neuropeptide found in the corpora cardiaca (CC) increases 34‐fold from larval instar III to late adult, with the greatest quantitative increase (3,000 pmol total in males) occurring during the 6 weeks of adult life. The Ro I: Ro II ratio also changes during development, from 5.4 in larval instar III to 2.0 in late instar V and finally to 4.0 in mature adults. Under physiological conditions these neuropeptides can be released from Romalea CC isolated in vitro, when the CC are depolarized with high‐potassium saline. This release is calcium‐dependent and 10% to 15% of the total peptide stores are mobilized during a 1‐hour treatment with high‐potassium, plus calcium, saline. More than one‐third of the mobilized peptide is released within the first 5 min. In locusts, release of the AKH peptides is reported to be mediated by the neurotransmitter octopamine, acting via the adenylate cyclase pathway. In Romalea, however, we find no evidence for either octopamine or cAMP‐mediated release of neuropeptide.