Effects of the NMDA receptor antagonist MK-801 on female reproduction and juvenile hormone biosynthesis in the cricket Gryllus bimaculatus and the butterfly Bicyclus anynana
Thorin L. Geister1,*,
Matthias W. Lorenz1,
Klaus H. Hoffmann1, and
Klaus Fischer1,2
1 Department of Animal Ecology I, University of Bayreuth, D-95440 Bayreuth,
Germany
2 Zoological Institute and Museum, University of Greifswald, D-17487 Greifswald,
Germany
*
Author for correspondence (e-mail:
thorin.geister{at}uni-bayreuth.de)
Accepted for publication 10 March 2008.
Abstract:
Apart from regulating insect development, juvenile hormones (JHs) play an
important role in insect reproduction, where they initiate vitellogenin
synthesis and regulate the uptake of yolk by the ovary. JH synthesis is a
tightly regulated process controlled by neurons and peptidergic neurosecretory
cells. One of the known stimulatory regulators of JH biosynthesis is
glutamate, and its N-methyl-D-aspartate (NMDA) receptor
has been recently found in the cockroach Diploptera punctata. In this
study we demonstrate a strong reduction in reproductive output in the tropical
butterfly Bicyclus anynana and the Mediterranean field cricket
Gryllus bimaculatus caused by the NMDA receptor antagonist MK-801.
Such inhibiting effects on reproduction could be overruled by the application
of JH mimics. In G. bimaculatus, MK-801 inhibits in vitro JH
biosynthesis in the corpora allata and reduces in vivo JH haemolymph
titres in a dose-dependent manner. These results suggest that JH biosynthesis
in the corpora allata is at least in part controlled by an NMDA receptor with
Ca2+ as a second level messenger. Based on our findings we consider
NMDA receptor antagonists as important tools for manipulating juvenile hormone
biosynthesis and therefore for gaining a better understanding of the
mechanistic basis of reproduction.
Key Words: fecundity • Corpora allata • glutamate receptor • insects
