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The effect of xylocaine injections on the rabbit's retina: Averaged ERG and etectronmicroscopy
1208
IUPS-ISCERG
Symposium Papers
the present investigation, isolate the receptor part of this component destroying the proximal part. The results might, however, indicate that P III in warm-blooded animals is merely generated by the receptors (BROW et al., 1965). To answer this question would require further investigation by means of microelectrode studies from the different retinal layers. REFERENCES AMES,A. III, TSUKADA,Y. and NESBE~, F. B. (1967). J. Neurochem. 14, 145. BROWN,K. T., WATANABE,K. and MURAKAMI, M. (1965). Cold Spring Ha&. Symp. Quunr. Biol. 30,457. HA-, R. and B~RN~CHUN, H. (1%5). Experientiu 21, 484. MURUCAMI, M. and KANHCO, A. (1966). Vision Res. 6,627. SILLMAN, A. J., ITO,H. and TOMITA, T. (1969). Vision Res. 9, 1443.
35 The effect of xylocaiw iqjecGcmson the rabbit’s retina: Avewed ERG ad ele&onmlcr~py N. STANGOS,P. REY, P. LEUENBERGER and S. KOROL. University Eye Clinic, Geneoa, Switzerland THE INJECTIONof O-01 g of xylocaine in the vitreous body is followed by a partial or total suppression of the b-wave. Recovery takes place and the b-wave displays the same amplitude after 5-8 hr. The quantitative analysis of the ERG (1) The average peak amplitude of the u-wave (20 rabbits) is slightly increased, but the difference is not statistically signi&tnt (p > 0.05). (2) The average latency of the u-wave is slightly increased. (3) The peak time of the a-wave is very much increased (p < 0.001). (4) The mean amplitude of the &wave is very much reduced (p < O*OOl). (5) The b-latency is increased Cp e 0401). (6) The oscillatory potentials are abolished when the b-wave is also suppressed. (7) In the first stage of recovery, the f&st oscillatory potential increases faster than the last two ones; the third one is the most sensitive to anesthesia. (8) There is a strong positive correlation, which is statistically certain, between the alatency and the peak times of the three oscillatory potentials; however, such a correlation is less and less strong from the first to the third oscillatory potential. (9) Implicit times of the first and second oscillatory potentials decrease with the increase of the stimulus brightness; such a relation is not found for the third oscillatory potential. (10) During recovery, oscillatory potentials are marked while the b-wave is still depressed. Electronmicroscopy gives the following results : (1) Neither the pigmentary epithelium, nor the horizontal and bipolar cells were destroyed by xylocaine injections. (2) In photoreceptors, external segment remained untouched and in two cases only, the internal segment showed an increased metabolic activity. (3) Systematic lesions were found only in the synapses between photoreceptors and bipolar and horizontal cells. Conclusion The averaged ERG can be thus interpreted as expressing a conduction blockage between photocells and inner nuclear layer:
IUPS-ISCERG SymposiumPapers
1209
(1) The a-wave corresponds to the activity of the photoreceptors;
the amplitude of the u-wave may be increased because of the slowing down of the b-wave. (2) The b-wave corresponds to the activity of the inner nuclear layer. (3) The oscillatory potentials originate from the same layer. (41 Oscillatory potentials originate from different cells groups and, according to DOWLING’S hypothesis (1970) the first two are more closely associated to the photoreceptors activity than the third one. (9 Concerning clinical purposes, a decreased amplitude of the b-wave should not be systematically interpreted as a destruction of the cells of the inner layer not as a lack of activity of these cells; when the a-wave is demonstrated as being normal, as it is the case here, a depression of the b-wave can be due to a lack in transmission fram the photoreceptors down. REFERENCE DOWLING,J. E. (1970). Organisation of vertebrate retina. Invest. Ophthal. 9, 655.
36 Proximal negative response in the pigeon retina A. L.
HOLDEN.
Institute of Ophthalmology, Judd St., London
THE PROXIMAL negative
response characterised by BURKHARDT (1970) in the frog retina has been investigated in the pigeon with intraretinal microelectrode recording. As in the frog it is localized in the retina proximal to the b-wave. It shows an area dependence different to that of the b-wave, and in its preference for small spots and its receptive field extent resembles the retinal ganglion cells. Two new findings are: (a) Its “on” and “off” transients show a differing depth distribution, with the “on” effect being localized vitreal to the “off” effect, (b) its threshold for large spots is higher than for small spots, suggesting the action of surround inhibition at or prior to the inner plexiform layer. REFERENCE BURKHARD~,D. A. (1970). J. Neurophysiol.
33,405-420.
37 Effect of barbiturates upon the ERG of mammalian retinas irr vitro Y. HONDA and M. NAGATA. Department of Ophthalmology, Faculty of Medicine, Kyoto
University, Sakyo-ku Kyoto, Japan IT IS known that barbiturates inhibit synaptic transmission in both the central and the autonomic nervous systems, resulting in anestheisa. This blocking effect of barbiturates has also been anticipated in some synapses between several kinds of retinal cells (NOELL, 1958; YONEMURA et al. 1966; BORNSCHEIN et al. 1966). The purpose of the present study is to explore the direct effect of phenobsrbit.Na. on the retinal action potential employing
IUPS-ISCERG
Symposium Papers
the present investigation, isolate the receptor part of this component destroying the proximal part. The results might, however, indicate that P III in warm-blooded animals is merely generated by the receptors (BROW et al., 1965). To answer this question would require further investigation by means of microelectrode studies from the different retinal layers. REFERENCES AMES,A. III, TSUKADA,Y. and NESBE~, F. B. (1967). J. Neurochem. 14, 145. BROWN,K. T., WATANABE,K. and MURAKAMI, M. (1965). Cold Spring Ha&. Symp. Quunr. Biol. 30,457. HA-, R. and B~RN~CHUN, H. (1%5). Experientiu 21, 484. MURUCAMI, M. and KANHCO, A. (1966). Vision Res. 6,627. SILLMAN, A. J., ITO,H. and TOMITA, T. (1969). Vision Res. 9, 1443.
35 The effect of xylocaiw iqjecGcmson the rabbit’s retina: Avewed ERG ad ele&onmlcr~py N. STANGOS,P. REY, P. LEUENBERGER and S. KOROL. University Eye Clinic, Geneoa, Switzerland THE INJECTIONof O-01 g of xylocaine in the vitreous body is followed by a partial or total suppression of the b-wave. Recovery takes place and the b-wave displays the same amplitude after 5-8 hr. The quantitative analysis of the ERG (1) The average peak amplitude of the u-wave (20 rabbits) is slightly increased, but the difference is not statistically signi&tnt (p > 0.05). (2) The average latency of the u-wave is slightly increased. (3) The peak time of the a-wave is very much increased (p < 0.001). (4) The mean amplitude of the &wave is very much reduced (p < O*OOl). (5) The b-latency is increased Cp e 0401). (6) The oscillatory potentials are abolished when the b-wave is also suppressed. (7) In the first stage of recovery, the f&st oscillatory potential increases faster than the last two ones; the third one is the most sensitive to anesthesia. (8) There is a strong positive correlation, which is statistically certain, between the alatency and the peak times of the three oscillatory potentials; however, such a correlation is less and less strong from the first to the third oscillatory potential. (9) Implicit times of the first and second oscillatory potentials decrease with the increase of the stimulus brightness; such a relation is not found for the third oscillatory potential. (10) During recovery, oscillatory potentials are marked while the b-wave is still depressed. Electronmicroscopy gives the following results : (1) Neither the pigmentary epithelium, nor the horizontal and bipolar cells were destroyed by xylocaine injections. (2) In photoreceptors, external segment remained untouched and in two cases only, the internal segment showed an increased metabolic activity. (3) Systematic lesions were found only in the synapses between photoreceptors and bipolar and horizontal cells. Conclusion The averaged ERG can be thus interpreted as expressing a conduction blockage between photocells and inner nuclear layer:
IUPS-ISCERG SymposiumPapers
1209
(1) The a-wave corresponds to the activity of the photoreceptors;
the amplitude of the u-wave may be increased because of the slowing down of the b-wave. (2) The b-wave corresponds to the activity of the inner nuclear layer. (3) The oscillatory potentials originate from the same layer. (41 Oscillatory potentials originate from different cells groups and, according to DOWLING’S hypothesis (1970) the first two are more closely associated to the photoreceptors activity than the third one. (9 Concerning clinical purposes, a decreased amplitude of the b-wave should not be systematically interpreted as a destruction of the cells of the inner layer not as a lack of activity of these cells; when the a-wave is demonstrated as being normal, as it is the case here, a depression of the b-wave can be due to a lack in transmission fram the photoreceptors down. REFERENCE DOWLING,J. E. (1970). Organisation of vertebrate retina. Invest. Ophthal. 9, 655.
36 Proximal negative response in the pigeon retina A. L.
HOLDEN.
Institute of Ophthalmology, Judd St., London
THE PROXIMAL negative
response characterised by BURKHARDT (1970) in the frog retina has been investigated in the pigeon with intraretinal microelectrode recording. As in the frog it is localized in the retina proximal to the b-wave. It shows an area dependence different to that of the b-wave, and in its preference for small spots and its receptive field extent resembles the retinal ganglion cells. Two new findings are: (a) Its “on” and “off” transients show a differing depth distribution, with the “on” effect being localized vitreal to the “off” effect, (b) its threshold for large spots is higher than for small spots, suggesting the action of surround inhibition at or prior to the inner plexiform layer. REFERENCE BURKHARD~,D. A. (1970). J. Neurophysiol.
33,405-420.
37 Effect of barbiturates upon the ERG of mammalian retinas irr vitro Y. HONDA and M. NAGATA. Department of Ophthalmology, Faculty of Medicine, Kyoto
University, Sakyo-ku Kyoto, Japan IT IS known that barbiturates inhibit synaptic transmission in both the central and the autonomic nervous systems, resulting in anestheisa. This blocking effect of barbiturates has also been anticipated in some synapses between several kinds of retinal cells (NOELL, 1958; YONEMURA et al. 1966; BORNSCHEIN et al. 1966). The purpose of the present study is to explore the direct effect of phenobsrbit.Na. on the retinal action potential employing