Ionotropic glutamate receptors mediate juvenile hormone synthesis in the cockroach, Diploptera punctata.
By monitoring changes in the cytosolic [Ca2+](i) 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 microM 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 [Ca2+](i) 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 microM kainate. Kainate had no stimulatory effect on JH synthesis in calcium-free medium. The kainate-induced JH synthesis was blocked by 20 microM CNQX but was not affected by 20 microM 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 calcium 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.
Chiang
Ann-Shyn
AS
Department of Life Science, National Tsing-Hua University, Hsinchu 300, Taiwan. aschiang@life.nthu.edu.tw
Pszczolkowski
Maciej A
MA
Liu
Hsin-Ping
HP
Lin
Shu-Chen
SC
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003058:Cockroaches / Q000187:drug effects / Q000378:metabolism*; D003335:Corpora Allata / Q000187:drug effects / Q000378:metabolism*; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005971:Glutamates; D007605:Juvenile Hormones / Q000096:biosynthesis*; D007608:Kainic Acid / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D016318:Quisqualic Acid / Q000494:pharmacology; D017470:Receptors, Glutamate / Q000378:metabolism*; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; D007605:Juvenile Hormones; D011810:Quinoxalines; D017470:Receptors, Glutamate; D018094:Receptors, Metabotropic Glutamate; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D016318:Quisqualic Acid; D007608:Kainic Acid; D002118:Calcium