Neural mechanisms conroling adult diapause in insects

本研究旨在探讨飞蝇原荷尔蒙生殖滞育的神经机制。用放射化学方法测定了滞育雌虫和生殖雌虫体内保幼激素(JH)的体外合成活性。在滞育条件下饲养的雌虫的JH合成活性增加，而在滞育诱导条件下饲养的前期成虫的JH合成活性保持在较低的水平。JH产量的降低是诱导滞育的原因之一。去掉大脑间部(PI)和外侧部(PL)神经元后的JH合成速率表明，这些神经元并不直接介导JH合成速率的变化，而是与一些未知的抑止和促通便因子协同调节卵巢的发育。通过细胞内记录和染色观察PI和PL神经元的形态和电学特性。鉴定出三种PI神经元和两种PL神经元。在这些神经元中，1个PI神经元的峰时长和1个PL神经元的峰高在滞育诱导和滞育回避条件下有显著差异。免疫细胞化学显示PI或PL神经元内有FMRFamide、β-色素分散激素、科拉西林和缩胆囊素样多肽。FMRFamide和脑叶在体外对JH的生物合成速率有微弱的抑制作用。本研究对PI和PL神经元的形态和电生理学特征进行了研究，并提出了在土星天牛生殖滞育的神经机制中控制JH合成速率的候选因素。

The present study was performed with an aim to investigate neural mechanisms underlying reproductive diapause in the blow fly, Protophormia terraenovae. In vitro synthetic activities of juvenile hormones (JH) were examined using a radiochemical assay in diapause females and reproductive females. JH synthetic activities increased in females reared under diapause-averting conditions and remained low in previtellogenic females reared under diapause-inducing conditions. A decrease in the JH production rate is a cause of diapause induction. JH synthetic rate after removal of the pars intercerebralis (PI) and pars lateralis (PL) neurons suggested that these neurons do not directly mediate changes in the JH production rate, but regulate ovarian development cooperatively with some unknown allatostatic and allatotropic factors. Morphological and electrical properties of PI and PL neurons were examined by intracellular recording and staining. Three types of PI and two types of PL neurons were identified. Among these neurons, one PI neuron showed significant differences in spike durations and one PL neuron in spike heights between diapause-inducing and diapause-averting conditions. FMRFamide, β-pigment-dispersing hormone, corazonin and cholecystokinin-like peptides were immunocytochemically revealed in the PI or PL neurons. FMRFamide and cerebral lobes weakly suppressed JH biosynthetic rates in vitro. The present study morphologically and electrophysiologically characterized PI and PL neurons, and showed candidates for factors controlling JH synthetic rates in neural mechanisms for reproductive diapause in P.terraenovae.