Title

Ionotropic glutamate receptors mediate juvenile hormone synthesis in the cockroach, Diploptera punctata

Abstract

By monitoring changes in the cytosolic [Ca ] and rates of juvenile hormone (JH) synthesis in response to L-glutamate agonists and antagonists, we identified and characterized glutamate receptor subtypes in corpus allatum (CA) cells of the cockroach, Diploptera punctata. During the first ovarian cycle, corpora allata exhibited a cycle of changes in sensitivity to L-glutamate correlated to cyclic changes in rates of JH synthesis. When exposed to 60 μM L-glutamate in vitro, the active corpora allata of day-4 mated females produced 60% more JH, while inactive corpora allata at other ages showed 10-20% stimulatory response. Pharmacological characterization using various L-glutamate receptor agonists and antagonists indicated that several ionotropic subtypes of L-glutamate receptors were present in the CA. The CA showed an increase in rates of JH synthesis in response to NMDA, kainate, and quisqualate, but not to AMPA in both L-15 medium and minimum incubation medium. In contrast, applications of the metabotropic receptor-specific agonist trans-ACPD failed to elicit a change in the cytosolic [Ca ] and JH production. An elevation of cytosolic calcium concentration, followed by 20-30% rise in JH production, was observed when active CA cells were exposed to 10-40 μM kainate. Kainate had no stimulatory effect on JH synthesis in calcium-free medium. The kainate-induced JH synthesis was blocked by 20 μM CNQX but was not affected by 20 μM NBQX. Kainate-stimulated JH production was not suppressed by MK-801 (a specific blocker of NMDA-receptor channel), nor was NMDA-stimulated JH production affected by CNQX (a specific antagonist of kainate receptor). These data suggest that active CA cells are stimulated to synthesize more JH by a glutamate-induced calciuin rise via NMDA-, kainate- and/or quisqualate-sensitive subtypes of ionotropic L-glutamate receptors. The metabotropic-subtype and ionotropic AMPA-subtype L-glutamate receptors are unlikely to be present on active CA cells. © 2002 Elsevier Science Ltd. All rights reserved. 2+ 2+ i i

Document Type

Article

DOI

https://doi.org/10.1016/S0965-1748(01)00146-1

Keywords

AMPA/kainate receptor, Calcium, Corpus allatum, Glutamate receptor, Juvenile hormone, L-Glutamate, NMDA receptor

Publication Date

6-15-2002

Journal Title

Insect Biochemistry and Molecular Biology

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