Neural mechanisms conroling adult diapause in insects

本研究旨在探讨土原蝇（protophoria terraenovae）生殖滞育的神经机制。用放射化学法测定了滞育雌虫和育龄雌虫体内幼体激素（JH）的体外合成活性。在避育条件下饲养的雌虫JH合成活性增加，而在诱导滞育条件下饲养的前卵生雌虫JH合成活性保持在较低水平。JH产率的降低是滞育诱导的原因之一。脑间部（PI）和侧部（PL）神经元去除后的JH合成率表明，这些神经元不直接介导JH产生率的变化，而是与一些未知的异化因子和异化因子协同调节卵巢发育。采用细胞内记录和染色法观察PI和PL神经元的形态学和电特性。鉴定出3种PI神经元和2种PL神经元。在诱导和避免滞育条件下，1个PI神经元的峰值持续时间和1个PL神经元的峰值高度存在显著差异。FMRFamide、β-色素分散激素、corazonin和胆囊收缩素样肽在PI或PL神经元中被免疫细胞化学发现。FMRFamide和脑叶微弱抑制体外JH生物合成率。本研究从形态学和电生理上对PI和PL神经元进行了表征，并在地背拟虾生殖滞育的神经机制中发现了控制JH合成率的候选因素。

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.