擺動美洲蟑螂觸角對其單眼神經巨大神經元訊息傳遞的影響

Effects on the Transmission of Ocellar L-neurons by Swinging the Antennae of American Cockroach Periplaneta americana

李明忠(Ming-Chung Lee) ； 李琦玫(Chi-Mei Lee) ； 柯孟昌(Meng-Chang Ko) ； 林金盾(Jin-Tun Lin) ； 童麗珠(Li-Chu Tung)

《台灣昆蟲》 28卷2期 (2008/10) Pp. 145-158

https://doi.org/10.6661/TESFE.2008012

摘要

觸角、單眼及複眼都是美洲蟑螂頭部重要的感覺器官。單眼及複眼都會對光照刺激產生反應，但就敏感度而言，單眼是複眼的數百倍。觸角則是頭部感受觸覺和嗅覺最主要的構造，表面分佈著許多形態各異的感覺毛。
單眼照光後，會產生一個過極化反應，藉由單眼神經內的巨大神經元將訊息從單眼傳入腦部；此時若再擺動蟑螂的觸角，則會誘發另一個明顯的去極化反應。此去極化反應會因灌流木防己苦毒素而受到抑制，且灌流濃度愈高，抑制的效果愈明顯；除此之外，產生反應所需的延遲時間也會隨著灌流藥物濃度的提高而逐漸增長。灌流高濃度的番木鱉鹼也會抑制上述去極化反應，但效果比灌流木防己苦毒素差，產生反應所需的延遲時間也沒有增長的現象。灌流其他化學藥品如bicuculline、bicucullin methiodide、beclofen、phaclofen 等，則對此因觸角擺動所引起的去極化反應無任何影響。
由上述結果可推測當觸角接受刺激後，除了將訊息送入中樞之外，還會另外再送一個訊息去抑制單眼訊息的輸入。這種抑制性的去極化反應可能是藉由活化單眼神經內巨大神經元上的伽馬氨基丁酸受器所產生；此種伽馬氨基丁酸受器的特性雖然較類似脊椎動物的伽馬氨基丁酸A型受器，但又不完全相同，可能是昆蟲所特有的一種受器。

關鍵字

觸角 ； 單眼 ； 木防己苦毒素 ； 番木鱉鹼 ； 伽馬氨基丁酸受器

並列摘要

The antennae, ocelli and compound eyes are all important sensors in the head of American cockroaches. Ocelli and compound eyes both react to illumination, but the ocelli are more sensitive than the compound eyes. Antennae are the main structures reacting to the stimulation of touch and smell, and there are many sensilla distributed on the surface of the antennae.
When the ocellus is being illuminated, it will induce a hyperpolarized membrane potential in the L-neuron of the ocellar nerves and sends a message from the ocellus to the brain. A swing of the antennae at that moment will induce another obviously depolarized membrane potential in the L-neurons. This depolarization will be inhibited by the perfusion of picrotoxin, and will be even more effective if perfused with a high concentration of picrotoxin. In addition, the delay in response time is prolonged according to the increase in concentration of the perfusion with picrotoxin. The depolarization will also be inhibited by perfusion with a high concentration of strychnine, but it is less effective than perfusion with picrotoxin and has no effect on the delaying time. There are no effects on the depolarization of the membrane potentials in the L-neurons induced by swinging the antennae after perfusion with other chemicals such as bicucullin, bicucullin methiodide, beclofen and phaclofen.
We conclude that besides sending messages to the brain, it induces another reaction to inhibit the message derived from the ocelli after the antennae are stimulated. This inhibited depolarization of the membrane potential might be induced by activating the GABA receptors in the ocellar L-neurons. The characters of these GABA receptors are similar to those of the GABA(subscript A) receptors in vertebrates, but both of them are not exactly the same. These GABA receptors might be peculiar to insects.

並列關鍵字

antenna ； ocellus ； picrotoxin ； strychnine ； GABA receptor