Action of Juvenile Hormone on the Cerebral Neurosecretory Cells of Mamestra brassicae in vivo and in vitro

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Abstract
The action of juvenile hormone (JH) on the accumulation and release of neurosecretory material in the cerebral neurosecretory cells of the cabbage armyworm, M. brassicae, was investigated. When a JH analogue (JHA, ZR-515) was injected into a 6-day-old last instar larva immediately following removal of the prothoracic glands, which normally causes the release of neurosecretory material from type II cerebral neurosecretory cells (type II-NSC), release of this material was inhibited and accumulation was observed in the type II-NSC. When JHA was injected into the larva 24 h after removal of the prothoracic glands, stainable neurosecretory material did not accumulate in the type II-NSC. Brains from 0-, 8-day-old last instar larvae and 1-day-old pupae cultured in vitro in medium containing JHA accumulated neurosecretory material in the type II-NSC. JHA effects on prothoracicotropic hormone (PTTH) release from the brains was examined by implantation experiments. Release of PTTH from the brains of 0-, 6-and 8-day-old last instar larvae was inhibited by JHA application. Probably, in the limited stages, JH inhibits PTTH release which seems to be released from the type II-NSC in M. brassicae, but may not affect synthesis of neurosecretory material in these cells.