Zoological Studies

Vol. 42 No. 2, 2003

Pharmacological Effects of Calcium Channel Antagonists on Juvenile Hormone Acid Release and Intracellular Calcium Level in the Corpora Allata of Adult Male Mythimna loreyi (Lepidoptera: Noctuidae)

Yi-Chung Hsieh1, Ying-Ru Chen2, Err-Lieh Hsu1 and Rong Kou2,*

1Department of Entomology, National Taiwan University, Taipei, Taiwan 106
2Institute of Zoology, Academia Sinica, Taipei, Taiwan 115

Yi-Chung Hsieh, Ying-Ru Chen, Err-Lieh Hsu and Rong Kou (2003) The pharmacological effects of calcium channel antagonists on the in vitro release of juvenile hormone acids (JHAs) and the intracellular calcium concentration ([Ca2+]i ) in corpora allata (CA) of Mythimna loreyi adult males were investigated in this study. Newly dissected CA were first incubated in medium 199 for 1 h for equilibration, CA were then transferred to fresh medium containing Ca2+ channel antagonists for another 3-h incubation. Most antagonists of the voltage-dependent calcium channel (VDCC) subtypes ( L-, N-, P-, Q-, R-, and T-types), at physiological doses, were unable to inhibit JHA release, except for diazoxide. Among the non-specific calcium channel antagonists, cadmium (Cd2+), cobalt (Co2+), and lanthanum (La3+) were effective inhibitors of JHA release. The effects of VDCC antagonists (i.e., diazoxide and verapamil) and non-specific calcium channel antagonists on [Ca2+]i were also measured in individual CA cells with Fura-2. Excised glands were first loaded with 20 M fura-2/AM in lepidopteran saline for 45 min at 28C in the dark. After hydrolysis, the [Ca2+]i was observed for 30 min. Diazoxide (10-4 M) initially caused a significant depression of [Ca2+]i , which then gradually increased to a normal level. Among the non-specific calcium channel antagonists, both Cd2+ and La3+ caused a significant depression of [Ca2+]i . Our results suggest the possible existence of some kind of calcium channel in the plasma membrane of CA cells.

Key words: Mythimna loreyi, Calcium channel antagonist, Corpora allata, Juvenile hormone acid, Intracellular calcium concentration.

*Correspondence: Tel: 886-2-27899541. Fax: 886-2-27858059. E-mail: kourong@gate.sinica.edu.tw