Ecdysteroids Regulate the Release and Action of Eclosion Hormone in the Moth Manduca sexta

Abstract

The regulation of hormone secretion often involves a complex interaction between neuroendocrine and endocrine centers. The classic example of such an interaction is between the vertebrate anterior pituitary and hypothalamus in which the cells of the former are regulated by peptides and amines that are released from neurosecretory cells in the latter [1,2]. These influences, however, are not unidirectional since the hormones released from endocrine glands may also act back on the central nervous system (CNS) to influence neurosecretory activity [2]. In insects, the existence of neurosecretory cells that release tropic hormones which then affect the activity of endocrine glands is well established. The best known example is the role of brain neurosecretory cells in regulating the secretory activity of the prothoracic glands [3]. There is now also a growing interest in insect endocrinology in how endocrine glands may in turn regulate neurosecretory centers in the CNS. One such example is the recent report that circulating ecdysteroids regulate the release of a myotropic peptide from the brain of female Rhodnius [4]. This paper will focus on another example in which ecdysteroids may control neuroendocrine function; in this case it involves the hormones involved in bringing a molt to its successful completion.