Neurosecretory cells in insect brain and production of hypoglycaemic hormone

Abstract

INSECTS have a hyperglycaemic hormone, produced by neurosecretory cells of the corpus cardiacum (CC). This hormone stimulates the production of the major blood carbohydrate trehalose from glycogen stored in fat body cells¹. No hypotrehalosaemic hormone has so far been reported and the level of blood trehalose has been thought to depend on: the secretory activity of the CC neurosecretory cells controlled by nerves from the brain^2,3; the relationship between production and consumption of trehalose, which in many insects, including flies, serves as fuel for flight. Also, in vitro experiments indicate that medium containing trehalose can inhibit the synthesis or liberation of trehalose from fat body cells, and it has been suggested that such feedback control is an important factor in the natural regulation of trehalose formation^4,5. It was therefore surprising to find that seven decapitated 6-d-old blowflies, Calliphora erythrocephala, not only remained alive for 30 h, during which locomotion and heart beat continued, but that their blood trehalose level had increased from 21.9 g l⁻¹ (± 4.09 s.e.m.) to 113.2 g l⁻¹ (± 9.07 s.e.m.).