The cholinergic system in insect diapause

Abstract

The presumed rôle of the cholinergic system in the regulation of pupal diapause was investigated by studying the spontaneous electrical activity in the brain and ventral ganglia of diapausing and developing H. cecropia, the activity of the cholinergic enzymes and the levels of cholinergic substance in brains and ganglia of different developmental stages of diapausing H. cecropia, A. polyphemus and A. pernyi; non-diapausing forms of A. polyphemus and A. pernyi, and of non-diapausing species G. mellonella and M. americanum. Electrical activity and cholinesterase and choline acetylase activity was demon-strated both in brains and ganglia, throughout diapause. On the termination of diapause and during adult development, the activity of the enzymes increased strikingly. Similar patterns of change in the cholinergic enzymes were also observed in the two non-diapausing forms of normally diapausing species and in the two non-diapausing species. The titer of the cholinergic substance was also very low during diapause but increased synchronously with the cholinergic enzymes during adult development. The DNA content, and total and soluble protein levels also remained constant during diapause but increased synchronously with the cholinergic enzymes during adult development. It is thus concluded that the observed changes in the cholinergic system are associated with the growth and development of the nervous system rather than with the mechanism of induction or termination of diapause.