Abstract
Axon processes of neurosecretory cells of the brain, distinguished by secretory granules with specific diameter, were investigated electron microscopically. Synapses from common neurone to neurosecretory axon were observed in the neuropile of the brain. Neurosecretory I cells and II cells in the pars intercerebralis, and neurosecretory IV cells in the dorso-lateral part of brain sent axons, through nervi corporis cardiaci I and II respectively, to the corpus cardiacum, and there they established axon terminals. Intrinsic neurosecretory cells with secretory granules with a diameter of 130-160mμ were also observed in the corpus cardiacum. The neurosecretory axon terminals at the corpus cardiacum were filled with secretory granules of various electron densities, and many synaptic vesicles (ca. 50mμ in diameter) also aggregated along the axon membranes. The appearance of these axon terminals, considered as for hormone release, were always observed from the prepupal to the earlier pupal stage of both diapause and non-diapause individuals. Characteristically, just after pupation of the non-diapause insect when neurosecretory materials were vigorously released, many vacuolated parts appeared in the axons of the neurosecretory II cell together with synaptic vesicles and secretory granules.
