. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 312 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS Reference: Biol Bull. 185: 312. (October. 1993) GABA Responses on Retinal Bipolar Cells Haohua Qian and John E. Dowling (The Biological Laboratories, Harvard University) GABA is the main inhibitory neurotransmitter in the central nervous system. Recently, a new type of GABA receptor, termed the GABAC receptor, has been reported (1-4). Unlike the well- characterized GABAA and GABAB receptors, GABAC receptors are insensitive to both bicuculline and baclofen, and are not modu
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 312 REPORTS FROM THE MBL GENERAL SCIENTIFIC MEETINGS Reference: Biol Bull. 185: 312. (October. 1993) GABA Responses on Retinal Bipolar Cells Haohua Qian and John E. Dowling (The Biological Laboratories, Harvard University) GABA is the main inhibitory neurotransmitter in the central nervous system. Recently, a new type of GABA receptor, termed the GABAC receptor, has been reported (1-4). Unlike the well- characterized GABAA and GABAB receptors, GABAC receptors are insensitive to both bicuculline and baclofen, and are not modulated by either the benzodiazepines or barbiturates. Al- though both GABAA and GABAC receptors are linked to chloride channels, a major difference between the responses of these two receptors is that GABAC responses are quite sustained, whereas GABAA responses desensitize substantially. Although GABAC receptors are especially prominent in retina (1-4), the distri- bution of these receptors on retinal neurons is largely unknown. The rod horizontal cells in perch retina possess only GABAC receptors, but bipolar cells in the same species appear to have both GABAA and GABAc receptors (1). In this study, the GABA responses of perch and bass bipolar cells were characterized, and the location of GABA receptors on the cells was determined. Solitary retinal neurons were enzymatically dissociated from both white perch (Roccus americana) and white bass (Morone chrysops)-stnped bass (Morone sa.\atilis) hybrid retinas. Bipolar cells were identified by their morphology. The membrane cur- rents were recorded using either conventional or amphotericin- perforated whole-cell voltage-clamp recordings. Application of 100 fiM GABA onto bipolar cells induced a chloride current that was blocked by picrotoxin. The GABA-induced currents had both transient and sustained components (Fig. la). The transient component was sensitive to bicuculline, whereas the more sustained component was resistant to bicuc
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