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1611 Visual accommodation reflex in a filefish, navodon modestus
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1611
V I S U A L A C C O M M O D A T I O N R E F L E X IN A F I L E F I S ! I, N:lvodon H I R O A K I S O M I Y A I, M A S A M I Y O S H I M O T O 2 A N D H I R O N O B U ~_Lab. o f Develop. Biotech., School o f Vet. Med., A z a b u University, S a g a m i h a m 2Dept. o f Anat. Nippon Medical School, Sendagi 1-1-5, B t m k y o - k u , T o k v o 1 13.
modestus. I T O 2, 229, Japan and Japan
Many teleosts have an intraocular lens muscle which causes lens movement for visual accommodation (Somiya 1987). Central pathways for visual accommodation were traced in the filefish (Navodon modestus) using horseradish peroxidase (HRP) [racing method. Following HRP injection into the lens muscle, large cells were labelled in the ciliary ganglion. After HRP injections into the ciliary ganglion, a compact cell group was retrogradely labelled in an area rostrodorsal to the somatic oculomotor nuclei in the midbrain. This nucleus was considered to be homologous with the mammalian Edinger-Westphal nucleus. Following injections of HRP into the Edinger-Westphal nucleus, cells in the nucleus of the posterior commissure were retrogradely labelled. Furthermore, injection of HRP into the nucleus of the posterior commissure, labelled fibers and terminals were observed in the Edinger-Westphal nucleus. Since the nucleus of the posterior commissure receives retinal projections (Ito et al. 1984), it is considered that" the cells in the nucleus of the posterior commissure are the first central neurons in the pathway for visual accommodation in teleosts.
1612
INPUT-OUTPUT RELATIONSHIPS OF THE AVIAN RETINOPETAL SYSTEM. HIROYUKI UCHIYAMA 1, NAOYUKI YAMAMOTO 1, MASAKI TAUCHI2 AND IIIRONOBU ITO I lDepartment of Anatomv and Laboratory for Comparative Neuromorphologv, Nippon Medical School, Tokvo 1 t3 and 2Research Institute, National Rehabilitation Center for the Disabled, Tokorozawa, 369, Japan. The isthmo-optic nucleus (ION) is the predominant origin of the centrifllgal fibers projecting to the avian retina. Stereotaxic injections of tracers (e.g. biocytin and tetramethylrhodamine-dextran) into the ION were performed in adult Japanese quail (Coturnix coturnix japonica) in order to investigate input-output relationships of the nucleus. The main input to the ION originate in the ipsilateral optic tectum I 1 I. The somata of the tectal neurons projecting to the ION (rectoION neurons) were located in lamina 9 of Ramrn y Cajal [21 (sublamina h of the stratum griseum et fibrosum superficiale (SGFS) of Cowan et al. [31). The tecto-ION neurons were distributed evenly throughout the optic rectum. The total cell number of tecto-lON neurons was estimated by counting the neurons in tangentially cut sections. The total cell number of the tecto-ION neurons was approximately the same as the total cell number of their targets, the ION neurons. Single ION neurons synapse with single target cells in the inner nuclear layer of the contralateral retina. These resuhs suggest that the avian retinopetal system may have parallel and discrete modules that are organized with a strict topography. [11 Uchiyama & Watanabe, Nettrosci. Left. 58, 381-385, 1985. 121 Ramrn y Cajal, tlistologei dtt Systeme NervetLr de 171omme et des Vertebres, Maloine. Paris, 191 I. [31 Cowan, Adamson & Powell, .I. Attar. 95, 545-563, 1961.
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MUSCARINIC CHOLINERGIC SUPPRESSION OF SYNAPTIC RESPONSES IN CULTURED VISUAL CORTICAL NEURONS. FUMITAKA KIMURA AND ROBERT W. BAUGHMAN, Department of Neurobiology, Harvard Medical School, Boston MA 02115 U.S.A.
Mammalian visual cortex receives a dense cholinergic innervation from nucleus basalis magnocellularis in the basal forebrain. Recent bz vivo studies demonstrated that acetylcholine (ACh) has a facilitatory effect on visually driven responses in a majority of cells. To better understand the mechanism of this modulatory effect of ACh, we decided to characterize the ACh effect on synaptic responses elicited by single neurorts and found that ACh has a strong suppressive effect on both EPSPs and IPSPs. Experiments were performed with cultured visual cortical neurons plated on glial islands. Recordings were made with two whole-cell patch pipettes in current clamp mode from a pair of neighboring cells after at least 1 week in culture. ACh suppressed 96% (n=70) of EPSPs and 73% (n=56) of IPSPs. This suppressive effect was dependent on the applied doses. From the dose response curve, ECs0 values for the suppression were 65nM and 700rim for EPSP znd IPSP, respectively. We then attempted to determine what types of ACh receptors are invol¢~d in this effect. By comparing ratios of displacement caused by three partially selective muscarinic antagonists (pirenzepine, methoctramine and 4-DAMP) against lt.tm of ACh, we concluded that suppression of EPSPs is mediated by m4 receptors and that of 1PSPs by ml receptors. This observation was further supported by an experiment using pertussis toxin, which blocks m2 and m4 pathways, where 7 of the ffEPSPs became insensitive to ACh. Furthermore, when cells are treated with 1-Oleoyl-2-acetylrac-glycerol (OAG), an activator of protein kinase C which is generally involved in ml responses, all IPSPs (n=4) were reduced, suggesting ml participation in ACh suppression of IPSPs.
1611
V I S U A L A C C O M M O D A T I O N R E F L E X IN A F I L E F I S ! I, N:lvodon H I R O A K I S O M I Y A I, M A S A M I Y O S H I M O T O 2 A N D H I R O N O B U ~_Lab. o f Develop. Biotech., School o f Vet. Med., A z a b u University, S a g a m i h a m 2Dept. o f Anat. Nippon Medical School, Sendagi 1-1-5, B t m k y o - k u , T o k v o 1 13.
modestus. I T O 2, 229, Japan and Japan
Many teleosts have an intraocular lens muscle which causes lens movement for visual accommodation (Somiya 1987). Central pathways for visual accommodation were traced in the filefish (Navodon modestus) using horseradish peroxidase (HRP) [racing method. Following HRP injection into the lens muscle, large cells were labelled in the ciliary ganglion. After HRP injections into the ciliary ganglion, a compact cell group was retrogradely labelled in an area rostrodorsal to the somatic oculomotor nuclei in the midbrain. This nucleus was considered to be homologous with the mammalian Edinger-Westphal nucleus. Following injections of HRP into the Edinger-Westphal nucleus, cells in the nucleus of the posterior commissure were retrogradely labelled. Furthermore, injection of HRP into the nucleus of the posterior commissure, labelled fibers and terminals were observed in the Edinger-Westphal nucleus. Since the nucleus of the posterior commissure receives retinal projections (Ito et al. 1984), it is considered that" the cells in the nucleus of the posterior commissure are the first central neurons in the pathway for visual accommodation in teleosts.
1612
INPUT-OUTPUT RELATIONSHIPS OF THE AVIAN RETINOPETAL SYSTEM. HIROYUKI UCHIYAMA 1, NAOYUKI YAMAMOTO 1, MASAKI TAUCHI2 AND IIIRONOBU ITO I lDepartment of Anatomv and Laboratory for Comparative Neuromorphologv, Nippon Medical School, Tokvo 1 t3 and 2Research Institute, National Rehabilitation Center for the Disabled, Tokorozawa, 369, Japan. The isthmo-optic nucleus (ION) is the predominant origin of the centrifllgal fibers projecting to the avian retina. Stereotaxic injections of tracers (e.g. biocytin and tetramethylrhodamine-dextran) into the ION were performed in adult Japanese quail (Coturnix coturnix japonica) in order to investigate input-output relationships of the nucleus. The main input to the ION originate in the ipsilateral optic tectum I 1 I. The somata of the tectal neurons projecting to the ION (rectoION neurons) were located in lamina 9 of Ramrn y Cajal [21 (sublamina h of the stratum griseum et fibrosum superficiale (SGFS) of Cowan et al. [31). The tecto-ION neurons were distributed evenly throughout the optic rectum. The total cell number of tecto-lON neurons was estimated by counting the neurons in tangentially cut sections. The total cell number of the tecto-ION neurons was approximately the same as the total cell number of their targets, the ION neurons. Single ION neurons synapse with single target cells in the inner nuclear layer of the contralateral retina. These resuhs suggest that the avian retinopetal system may have parallel and discrete modules that are organized with a strict topography. [11 Uchiyama & Watanabe, Nettrosci. Left. 58, 381-385, 1985. 121 Ramrn y Cajal, tlistologei dtt Systeme NervetLr de 171omme et des Vertebres, Maloine. Paris, 191 I. [31 Cowan, Adamson & Powell, .I. Attar. 95, 545-563, 1961.
1613
MUSCARINIC CHOLINERGIC SUPPRESSION OF SYNAPTIC RESPONSES IN CULTURED VISUAL CORTICAL NEURONS. FUMITAKA KIMURA AND ROBERT W. BAUGHMAN, Department of Neurobiology, Harvard Medical School, Boston MA 02115 U.S.A.
Mammalian visual cortex receives a dense cholinergic innervation from nucleus basalis magnocellularis in the basal forebrain. Recent bz vivo studies demonstrated that acetylcholine (ACh) has a facilitatory effect on visually driven responses in a majority of cells. To better understand the mechanism of this modulatory effect of ACh, we decided to characterize the ACh effect on synaptic responses elicited by single neurorts and found that ACh has a strong suppressive effect on both EPSPs and IPSPs. Experiments were performed with cultured visual cortical neurons plated on glial islands. Recordings were made with two whole-cell patch pipettes in current clamp mode from a pair of neighboring cells after at least 1 week in culture. ACh suppressed 96% (n=70) of EPSPs and 73% (n=56) of IPSPs. This suppressive effect was dependent on the applied doses. From the dose response curve, ECs0 values for the suppression were 65nM and 700rim for EPSP znd IPSP, respectively. We then attempted to determine what types of ACh receptors are invol¢~d in this effect. By comparing ratios of displacement caused by three partially selective muscarinic antagonists (pirenzepine, methoctramine and 4-DAMP) against lt.tm of ACh, we concluded that suppression of EPSPs is mediated by m4 receptors and that of 1PSPs by ml receptors. This observation was further supported by an experiment using pertussis toxin, which blocks m2 and m4 pathways, where 7 of the ffEPSPs became insensitive to ACh. Furthermore, when cells are treated with 1-Oleoyl-2-acetylrac-glycerol (OAG), an activator of protein kinase C which is generally involved in ml responses, all IPSPs (n=4) were reduced, suggesting ml participation in ACh suppression of IPSPs.