The protocerebral neurosecretory system and associated cerebral neurohemal area of Acheta domesticus

PubMed ID: 4130595Six principal types of neurons are recognized in the median neurosecretory-cell group of the pars intercerebralis in the house cricket, Acheta domesticus. Four of the six cell types are neurosecretory neurons. The majority of the 900 cells contain granules 1500-3000 Å in diameter and are designated as type I. These neurons, which are associated with the nervus corporis cardiaci I (NCCI), undergo asynchronous secretory cycles. Two cell types (II and IV), which contain 700-1600 Å granules, terminate in a neurohemal area on the ventral median surface of the brain, a site not previously recognized as neurohemal in insects. Neurosecretory axons that lie within and below the perineurial sheath in the cerebral neurohemal area contain typical synaptoid figures, but no evidence of exocytosis was found. A single pair of neurosecretory cells (type III) has been recognized only from light microscope sections. Two distinct types of vesicle-bearing axons occur in protocerebral neuropile. The majority contain electron-dense and dense-cored vesicles 600-1000 Å in diameter. Some axons contain granules of type I cells and may be collaterals or loops of NCCI axons. © 1973 Springer-Verlag