Neurophysiological events during larval diapause and metamorphosis of the European corn borer, Ostrinia nubilalis Hübner

Abstract

The suggested role of the cholinergic system in the induction and termination of diapause was examined in the larval diapause of Ostrinia nubilalis. Spontaneous electrical activity, and low levels of cholinesterase activity, choline acetylase activity, and a cholinergic substance were demonstrated throughout in the brains of the fifth-instar larvae, regardless of whether diapause intervened or was prevented. On the termination of diapause, activity of the enzymes remained unchanged in the prepupal and pupal brains. However, developing brains of pharate adults showed sharp increases of eight to eleven times in the components of the cholinergic system. It is thus concluded that the observed changes in the cholinergic system have no role in the mechanism of induction or termination of the larval diapause.