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1639 Plastic nature of apb-sensitive conductance-decreasing synaptic receptor in retinal horizontal cells
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1638
MARKED INCREASE IN [3H](R)ot-METHYLHISTAMINEBINDING IN THE SUPERIOR COLLICULUS OF VISUALLY DEPRIVED RATS AFTER UNILATERAL ENqJCLEATION. YOICHI NAKAGAWAI, KAZUHIKO YANAI2, MOTOHI RO KIYOSAWA3AND TAKEHtKO WATANABE2,
Department.qof JOphthalmology and.2PharmacologyI, Tohoku University School of Medicine, Sendai 980 and ~Departmentof Ophthalmolo~oy,Tokyo Medical and Dental University School of Medicine, Tokyo 113, Japan Using quantitative autoradiography, the binding of [3H](R)ot-methylhistamineto histamine Hfreceptors in visual structures of unilaterally enucleated rats was examined to clarify the involvement of histamine neurons in the visual system. Five, 15, 30 and 45 days after unilateral enucleation, [3H](R)ot-methylhistaminebinding in the visually deprived superior colliculus, contralateral to the enucleated eye, was significantly increased. Slight time-dependent increase in ligand binding were observed in the visual cortex, but the change was significant only 45 days after unilateral enucleation. Unilateral enucleation had no significant effect on the binding in the dorsal lateral geniculate nucleus at any time after enucleation. Continuous injection of (S)-ot-fluoromethylhistidine (FMH), a specific inhibitor of L-histidine de.carboxylase, attenuated the effect of unilateral enucleation in the superior colliculus. These results suggest that retinal deafferentation induced an increase in histamine H3receptor binding sites, probably by selective adjustment of histamine neurons in response to unilateral enucleation.
1639
PLASTIC NATURE OF APB-SENSITIVE CONDUCTANCE-DECREASING SYNAPTIC RECEPTOR IN RETINAL H O R I Z O N T A L CELLS. M A S A H I R O YAMADA and *SYOZO YASUI, Electrotech. Lab., Tsukuba. Ibaraki 305, Japan and *K'v'ushu Inst. ofTech., Iizuka. Fukuoka 820, Japan.
We have recently shmvTa in the carp retina that synaptie transmission to H1 horizontal cells (HCs) from short-wavelength sensitive cones is a conductance-decreasing, sign-inverting type with 2-amino-4-phosphonobutyrate (APB) as an agonist, unlike the conventional exitatory synapse made by red cones. In this study, receptive field (RF) to blue stimuli was found to be smaller than to red. During the course of dark adaptation, the RF size became bigger, but the chromatic difference decreased. The RF size was reduced significantly immediately after adaptation with bright light. 1 mM APB slowly but greatly expanded the RF, much more to blue stimulus, and suppressed chromatic difference both in the RF size and in input resistance to chromatic stimuli, and had no effect on dye diffusion through gap junctions (thus, no effect on gap junctional resistance, Rg). It is suggested that the expansion of the RF size (the space constant oc4 tOn/Rg ) brought about by APB was due to an increase in the resistance of the subsynaptic membrane (Rm), thus, closure of channels associated with APB-sensitive synapse. Chromatic differences in the RF size are generated when this receptor mechanism is active in the light-adapted retina. (Co-operative study with *TETSUO FURUKAWA and MUSTAFA B.A. DJAMGOZ, Dept. of Biol.,Imperial Coll., London SW7 2BB, U.K.)
1640
T H R E E DIMENSIONAL DENDRITIC S T R U C T U R E OF T H E LONG SURVIVED A X O T O M I Z E D R E T I N A L GANGLION CELLS IN T H E M A M M A L I A N RETINA MASAKI TAUCHI Dept. of Sensory_ Impairments, Res. Inst., Natl. Rehab. Center for the Disabled, Namiki, Tokorozawa 359, Japan To study dendritic structure of the axotomized, long-survived retinal ganglion ceils in the rat retina, lucifer dye and neurobiotin were injected into single cells. Optic nerve of the adult rat (Wister strain, 70 days) was sectioned 2-3 mm behind the eyeball and fluorescent tracers (granular blue or tetrametylrhodamine-dextran) were applied to the stump of the optic nerve to retrogradely label the whole ganglion cell population. Leaving animals for 3 months after the operation, retinas were removed and the fluorescently labeled survived cells were injected with lucifer or neurobiotin for three-dimensional analysis by confocal microscope as well as computerized video image reconstructing system. In those cells survived relatively long period after the optic nerve section, there were at least three morphologically distinctive cell type in respects to dendritic structure; (I) nomal, (2)-shrunken, and (3) supposedly outgrown processes. We have analyzed third type neurons threedimensionally and found that their dendrites run unusual manner going up and down, and back and forth mainly within the inner plexiform layer.
1638
MARKED INCREASE IN [3H](R)ot-METHYLHISTAMINEBINDING IN THE SUPERIOR COLLICULUS OF VISUALLY DEPRIVED RATS AFTER UNILATERAL ENqJCLEATION. YOICHI NAKAGAWAI, KAZUHIKO YANAI2, MOTOHI RO KIYOSAWA3AND TAKEHtKO WATANABE2,
Department.qof JOphthalmology and.2PharmacologyI, Tohoku University School of Medicine, Sendai 980 and ~Departmentof Ophthalmolo~oy,Tokyo Medical and Dental University School of Medicine, Tokyo 113, Japan Using quantitative autoradiography, the binding of [3H](R)ot-methylhistamineto histamine Hfreceptors in visual structures of unilaterally enucleated rats was examined to clarify the involvement of histamine neurons in the visual system. Five, 15, 30 and 45 days after unilateral enucleation, [3H](R)ot-methylhistaminebinding in the visually deprived superior colliculus, contralateral to the enucleated eye, was significantly increased. Slight time-dependent increase in ligand binding were observed in the visual cortex, but the change was significant only 45 days after unilateral enucleation. Unilateral enucleation had no significant effect on the binding in the dorsal lateral geniculate nucleus at any time after enucleation. Continuous injection of (S)-ot-fluoromethylhistidine (FMH), a specific inhibitor of L-histidine de.carboxylase, attenuated the effect of unilateral enucleation in the superior colliculus. These results suggest that retinal deafferentation induced an increase in histamine H3receptor binding sites, probably by selective adjustment of histamine neurons in response to unilateral enucleation.
1639
PLASTIC NATURE OF APB-SENSITIVE CONDUCTANCE-DECREASING SYNAPTIC RECEPTOR IN RETINAL H O R I Z O N T A L CELLS. M A S A H I R O YAMADA and *SYOZO YASUI, Electrotech. Lab., Tsukuba. Ibaraki 305, Japan and *K'v'ushu Inst. ofTech., Iizuka. Fukuoka 820, Japan.
We have recently shmvTa in the carp retina that synaptie transmission to H1 horizontal cells (HCs) from short-wavelength sensitive cones is a conductance-decreasing, sign-inverting type with 2-amino-4-phosphonobutyrate (APB) as an agonist, unlike the conventional exitatory synapse made by red cones. In this study, receptive field (RF) to blue stimuli was found to be smaller than to red. During the course of dark adaptation, the RF size became bigger, but the chromatic difference decreased. The RF size was reduced significantly immediately after adaptation with bright light. 1 mM APB slowly but greatly expanded the RF, much more to blue stimulus, and suppressed chromatic difference both in the RF size and in input resistance to chromatic stimuli, and had no effect on dye diffusion through gap junctions (thus, no effect on gap junctional resistance, Rg). It is suggested that the expansion of the RF size (the space constant oc4 tOn/Rg ) brought about by APB was due to an increase in the resistance of the subsynaptic membrane (Rm), thus, closure of channels associated with APB-sensitive synapse. Chromatic differences in the RF size are generated when this receptor mechanism is active in the light-adapted retina. (Co-operative study with *TETSUO FURUKAWA and MUSTAFA B.A. DJAMGOZ, Dept. of Biol.,Imperial Coll., London SW7 2BB, U.K.)
1640
T H R E E DIMENSIONAL DENDRITIC S T R U C T U R E OF T H E LONG SURVIVED A X O T O M I Z E D R E T I N A L GANGLION CELLS IN T H E M A M M A L I A N RETINA MASAKI TAUCHI Dept. of Sensory_ Impairments, Res. Inst., Natl. Rehab. Center for the Disabled, Namiki, Tokorozawa 359, Japan To study dendritic structure of the axotomized, long-survived retinal ganglion ceils in the rat retina, lucifer dye and neurobiotin were injected into single cells. Optic nerve of the adult rat (Wister strain, 70 days) was sectioned 2-3 mm behind the eyeball and fluorescent tracers (granular blue or tetrametylrhodamine-dextran) were applied to the stump of the optic nerve to retrogradely label the whole ganglion cell population. Leaving animals for 3 months after the operation, retinas were removed and the fluorescently labeled survived cells were injected with lucifer or neurobiotin for three-dimensional analysis by confocal microscope as well as computerized video image reconstructing system. In those cells survived relatively long period after the optic nerve section, there were at least three morphologically distinctive cell type in respects to dendritic structure; (I) nomal, (2)-shrunken, and (3) supposedly outgrown processes. We have analyzed third type neurons threedimensionally and found that their dendrites run unusual manner going up and down, and back and forth mainly within the inner plexiform layer.