The molting gland of the cockroach Periplaneta americana: secretory activity and its regulation.

1. The prothoracic gland is the main source of ecdysteroids in larvae of the cockroach Periplaneta americana. 2. Besides ecdysone the molting gland of Periplaneta secretes 3-dehydroecdysone and proteins. 3. The molting gland of Periplaneta is regulated in different successive steps of cooperation of nervous and neuroendocrine activity. 4. Neurogenic effects on the molting gland via the prothoracic gland nerves are concentrated on the period of prepeak production of ecdysteroids. 5. Prior to the 17th day, the glands secretory activity is inhibited by GABA-ergic neuronal pathways from the subesophageal ganglion. 6. Neurogenic disinhibition by a peptidergic brain factor elicits the competence of the gland for prepeak activity, completed by the glandotropic effect of PTTH. 7. The 17th day of the larval stage is characterized as the head critical period, i.e., after this period the ecdysteroid secretion of the gland is independent of the prothoracicotropic hormone (PTTH) from the brain. 8. The main peak of ecdysteroid production is regulated by prothoracicotropic neuropeptids from the brain.