Voltage-Dependent Sodium and Calcium Channels of the Corpora Allata of the Cockroach Diploptera Punctata

Abstract

The corpora allata (CA) of Diploptera punctata are endocrine glands that synthesize and release juvenile hormone (JH). In mated females, cyclical changes in JH biosynthesis and titre have been correlated with the gonotrophic cycle (Tobe et al., 1985). Calcium ions (Ca2+) appear to contribute to control of JH biosynthesis in this species (Kikukawa et al., 1987). For example, an optimal concentration (3–5mM) of extracellular Ca2+ is required for maximal rates o JH biosynthesis and in the absence of extracellular Ca2+, JH biosynthesis is totally inhibited (Kikukawa et al., 1987). Thus, it seems likely that Ca2+ modulates JH biosynthesis, in part by transport of Ca2+ across the plasma membrane of the CA cells. This paper describes types of ion channels that may be involved in Ca2+ transport into the cells of the CA. Previous work (Thompson and Tobe, 1986) has provided evidence for the existence of voltage-dependent Ca2+ channels in the CA. The following work has employed an experimental protocol modified from Thompson and Tobe (1986); the results confirm and extend previous observations.