Stuart Ann E, Mekeel Harold E, Kempter Elizabeth
Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7545, USA.
Biol Bull. 2002 Feb;202(1):53-60. doi: 10.2307/1543222.
The photoreceptors of adult barnacles use histamine as their neurotransmitter and take up (3)H-histamine selectively from the extracellular medium. We assayed for the uptake of (3)H-histamine into the eyes of the free-swimming (nauplius) and settling (cyprid) larval stages of Balanus amphitrite. The extracellular space of nauplii proved permeable to dyes below about 800 molecular weight (MW), indicating that (3)H-histamine (MW 111) introduced into seawater would have access to internal structures. (3)H-Histamine was taken up into nauplii by a process with a K(D) of 0.32 microM. Uptake was antagonized by chlorpromazine, which also blocks uptake of (3)H-histamine into adult photoreceptors. In autoradiographs of serial sections of nauplii and cyprids incubated in (3)H-histamine, the ocelli and compound eyes were labeled; other structures in the animal were not. No eyes or other structures were labeled with (3)H-serotonin, a related amine whose transporter commonly transports histamine as well. These experiments show that a histamine-specific transporter similar to that found in the adult is expressed in all of the eyes of barnacle larvae. In the ocelli, where photoreceptors and pigment cells may be distinguished in the light microscope, label was unexpectedly concentrated far more over the pigment cells than over the photoreceptors.
成年藤壶的光感受器以组胺作为神经递质，并能从细胞外介质中选择性摄取³H-组胺。我们检测了³H-组胺在藤壶（Balanus amphitrite）自由游动的无节幼体和固着的腺介幼体阶段的眼睛中的摄取情况。结果表明，分子量低于约800的染料可透过无节幼体的细胞外间隙，这意味着引入海水中的³H-组胺（分子量111）能够进入内部结构。³H-组胺以KD为0.32微摩尔的过程被摄取到无节幼体中。氯丙嗪可拮抗摄取过程，它也能阻断³H-组胺进入成年光感受器。在³H-组胺中孵育的无节幼体和腺介幼体连续切片的放射自显影片中，单眼和复眼被标记；动物体内的其他结构未被标记。³H-5-羟色胺（一种相关胺类，其转运体通常也转运组胺）未标记任何眼睛或其他结构。这些实验表明，藤壶幼虫所有眼睛中都表达了一种与成年藤壶中发现的类似的组胺特异性转运体。在单眼中，在光学显微镜下可区分光感受器和色素细胞，出乎意料的是，标记物在色素细胞上的集中程度远高于光感受器。
