Analysis of spectral opponent mechanism in the optic lobe of the butterfly, Papilio xuthus

光谱对抗反应已在蝴蝶的光感受器水平上观察到。为了解释其机制，我提出了一个“组胺假说”：对抗性可能归因于光感受器之间通过激活组胺能通道的拮抗相互作用。组胺门控氯离子通道的免疫定位表明，蝶叶单极细胞（LMCs）和光感受器分别表达PxHCLA和PxHCLB。通过注射电流的微电极记录，当膜电位接近氯离子平衡电位时，lmc和光谱上对立的光感受器的响应都可以逆转。细胞内记录显示，lmc分为非谱对抗型和谱对抗型。前者包括三个光谱异构类，它们是与母型相关的。这表明lmc似乎通过PxHCLA整合来自同一小眼膜的光感受器的颜色信号。我还将LMC光谱类型与形态类型进行了关联。光谱上对立的lmc和可变光谱类别的发现为lmc在颜色信号通路中的作用提供了新的见解。此外，还记录了几种光谱上对立的光感受器。记录的对手反应可以很好地解释通过PxHCLB的ommatidial类型特异性光感受器间突触连接。本项目的研究结果将为进一步研究昆虫的早期着色加工提供一个跳板。

Spectral opponent responses have been observed at the level of photoreceptors in butterflies. To explain its mechanism, I proposed a “histamine hypothesis”: the opponency may be attributed to the antagonistic interaction between photoreceptors via the activation of histaminergic channels.Immunolocalization on histamine-gated chloride channels in Papilio xuthus suggested that the lamina monopolar cells (LMCs) and photoreceptors express PxHCLA and PxHCLB, respectively. Using sharp microelectrode recording with current injections, the responses of both LMCs and spectrally opponent photoreceptors could be reversed when the membrane potential was close to the equilibrium potential of chloride ions.Intracellular recording in the lamina showed that LMCs are divided into non-spectrally opponent and spectrally opponent ones. The former includes three spectrally heterogeneous classes, which are ommatidial type dependent. It suggests that LMCs seem to integrate chromatic signals from the photoreceptors in the same ommatidium via PxHCLA. I also correlated LMC spectral types with morphological types. The findings of spectrally opponent LMCs and variable spectral classes provide a new insight into the role of LMCs in color signaling circuitry. In addition, several classes of spectrally opponent photoreceptors were recorded. The recorded opponent responses can be well explained by the ommatidial type-specific inter-photoreceptor synaptic connections via PxHCLB. The results presented in this project will be a springboard for future studies of early chromatic processing in insects.