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Strain differences and kainic acid neurotoxicity
Brain Research, 166 (1979) 431-435
431
© Elsevier/North-Holland Biomedical Press
Strain differences and kainic acid neurotoxicity
PAUL R. SANBERG, MICHELE PISA and EDITH G. McGEER Kinsmen Laboratory of Neurological Research, Department of Psychiatry, University of British Columbia, Vancouver, B.C. V6T IW5 (Canada)
(Accepted December 21st, 1978)
Since Olney's original report 10 on the specific toxic effects of kainic acid (KA) on neuronal perikarya, several studies have been conducted in different laboratories on the anatomical1-3,5,16 and biochemical1,6,7,12,15 effects of KA injections into the neostriatum (CP). Much of the variability in the magnitude of the resulting lesions can be undoubtedly attributed to the use of different doses, volumes and rates of injections of the KA solution. It has in fact been shown that each of these injection parameters can remarkably affect the extent of neuronal loss in the CP 7. Recent observations, however, suggested that a genetic factor may also influence the neurotoxic effectiveness of KA. Thus, it was noted that identical neostriatal injections resulted in a more severe aphagia and adipsia, and in a higher mortality rate in hooded than in Wistar rats (Sanberg and Corcoran, unpublished data). It also appeared that different litters of rats of the same Wistar strain might show considerable differences in the extent of CP damage after identical injections of KA (Pisa, Sanberg and Fibiger, unpublished data). Also, investigators using Wistar rats3, 5-7 have reported CP lesions of similar extent to that found by other investigators using Sprague-Dawley rats 1,2, 15,16, even though widely different injection parameters were used. Here we report biochemical data indicating that strain differences in sensitivity to KA are indeed another factor to be considered in comparing data of various laboratories. Male Wistar albino rats (Woodlyn Farms, Guelph, Ontario), SpragueDawley albino rats (Biobreeding Labs, Ottawa, Ontario), and Chester-Beatty hooded rats (Biobreeding Labs, Ottawa, Ontario) weighing approximately 300 g at the time of surgery were included in the study. After anesthesia with pentobarbital (50 mg/kg i.p.) the rats were given unilateral intrastriatal injections of either 2.5 or 5.0 nmol of KA (Sigma Chemical Co.) dissolved in 1.0 #1 of phosphate buffered saline solution, pH 7.2, through a 34 gauge cannula over a 5-min period. The cannula was left in place for a further 1 min to allow diffusion of the drug solution. With the incisor bar at 4.2 mm below the interaural line, coordinates used were AP +9.6 and DV +4.5, with reference to the interaural line; and ML --2.8, with reference to the sagittal suture. The rats were operated in two series and an interval of either I0 or 18 days separated surgery from sacrifice. Rats were killed by cervical fracture, and the CP was bilaterally dissected, weighed, and homogenized in 10 vol of either 0.25 M or (for uptake assays)
432 TABLE I
Neurochemical parameters in the control, noninjected neostriatum of rats of 3 different strains The contralateral side was injected with either 2.5 or 5 nmol of kainic acid at least 10 days prior to sacrifice. Values represent means ± S,E.M. Protein content was measured on a wet tissue weight basis. Enzymes and glutamate uptake were measured on a protein content basis.
Dose
Strain Sprague-Dawley (n)
Wistar (n)
Chester Beatty (n)
10.54 31.28 12.89 3012
i 0.20 ± 0.36 -4- 0.59 5- 204
(10) (10) (10) (5)
10.52 34.96 14.68 2999
± i 5:k
0.28 1.66 0.26 202
(10) (10) (10) (5)
10.25 5- 0.26 35.21 5- 0.96 13.58 5- 0.24 --
(5) (5) (5)
9.85 31.33 13.48 2761
5± ± ±
(8) (8) (8) (3)
10.52 32.99 14.83 3067
5± :k ~
0.42 1.45 0.36 154
(10) (10) (10) (5)
10.68 4- 0.30 34.66 ± 0.93 13.46 5- 0.36 --
(4) (4) (4)
2.5 nmole KA Protein mg/g CAT*,** GAD*,** Glutamate uptake**
5.0 nmole K,4 Protein mg/g CAT*,** GAD*,** Glutamate uptake**
0.35 0.57 0.41 152
* Significant strain differences, P < 0.01. ** in/Lmol'h-l'100 mg.protein-I.
0.32 M of sucrose. The activities of the two neurotransmitter synthesizing enzymes choline acetyltransferase (CAT) and glutamic acid decarboxylase (GAD), commonly considered as functional indicators of cholinergic and GABAergic neurons respectively, were measured by previously reported radioenzymatic assay methods s. Protein content was measured according to Lowry et al ~. In the rats of the second series high affinity glutamate uptake, a functional indicator of presumably glutamatergic corticostriatal afferent terminals 9, was also measured as previously reported 9, using samples of a homogenate of the P2 pellet fraction and sodium-free blanks. Since the trend of the results was similar in both series, the data of the two series combined are reported. For rats of the Chester-Beatty hooded strain only data from the first series are available, since 8 out of 10 rats operated in the second series died within a few days after surgery. Data were analyzed with two-way analyses of variance, with Strains and Dose as main Factors, using an unweighted means solution. Multiple comparisons between strains were conducted using Scheff6's F test. Since this test is more rigorous than other methods of multiple comparisons a 10 ~ significance level was accepted 14. Data for non-injected CP are shown in Table I. There were no significant effects of strains on either protein content, F < 1, or glutamate uptake, F < 1. However, rats of different strains significantly differed in both CAT and G A D activities, F = 4.4 and 8.6 respectively, df = 2,44; P < 0.01. Multiple comparisons between strains revealed that Sprague-Dawley rats had significantly less CAT activity than either Wistar or Chester-Beatty rats. Also, both Sprague-Dawley and Chester-Beatty rats had less G A D activity than Wistar rats. Neither the main effect of dose nor the interaction term were significant for any of the indices measured, F's < 1.
433 TABLE II Neurochemical parameters in the kahlic acid injected neostriatum of rats of 3 different strains
Values are expressed as mean percentages ± S.E.M. of the related values in the contralateral noninjected neostriatum. Dose
Strain Sprague-Dawley (n)
Wistar (n)
Chester-Beatty (n)
2.5 nmole KA
Protein mg/g CAT**,*** GAD**,*** Glutamate uptake
101.8 ± 3.6 73.9 ± 2.9 75.9 zk 3.1 88.2 4, 6.2
(10) (10) (10) (5)
97.6 4. 59.3 4, 65.1 4. 102.0 4,
(8) (8) (8) (3)
96.8 ± 4.0 (10) 59.7 ± 2.1 (10) 61.4 4. 2.3 (10) 95.8 4, 7.83 (5)
101.7 ± 5.5 (5) 54.6 4. 1.9 (5) 57.7 4. 1.6 (5) --
5.0 nmole KA
Protein mg/g* CAT**,*** GAD**,*** Glutamate uptake
4.9 3.7 3.2 2.2
85.9 4- 3.5 40.2 4, 3.6 47.9 4, 3.3 103.3 4. 1.8
(10) (10) (10) (5)
104.7 4, 1.0 (4) 47.9 4- 1.3 (4) 51.8 4. 3.3 (4) --
* significant strain differences, P < 0.05. significant strain differences, P < 0.005. *** significantly different from lower dose, P < 0.005. **
Table II shows data in the injected CP, expressed as percentages o f the related values in the noninjected CP. Analysis of variance o f the protein data revealed a significant effect o f strain, F = 3.8; df = 2,41; p < 0.05. Multiple comparisons between strains indicated a significantly greater decrease of protein content in the Wistar than in the Chester-Beatty rats. N o other comparison attained the 1 0 ~ level of significance. Both the main effect o f dose and the interaction term were not significant, F ' s < 1. There were no significant differences in protein content between the injected CP and their corresponding control CP in either strain. The difference in the injected CP protein content between the Wistar strain and the Chester-Beatty strain rats m a y reflect greater edema in the injected CP o f the Wistar rats during the acute stages following the K A injections. There were no reliable differences between Sprague-Dawley and Wistar rats in glutamate uptake in the injected CP, F < 1, at either dose, F = 3.07; df = 1,14. Indeed, in agreement with previous findings 7, K A injections did not affect glutamate uptake, as shown by the lack o f substantial differences between control and injected CP in uptake values. As expected1,5-7,12,15, the rats o f all groups revealed a marked decrease in both C A T and G A D activities in the injected CP. The main finding was a significant effect o f strain on the decrease o f b o t h C A T and G A D activities, F = 18.9 and 18.7 respectively, df = 2,41 ; P < 0.0005. Multiple comparisons between strains indicated that this effect mainly resulted f r o m a significantly smaller decrease of both enzymes in S p r a g u e - D a w l e y rats c o m p a r e d with rats o f the other two strains. Both C A T and G A D decreased significantly more in the rats treated with the higher dose o f K A ,
434 F = 32.7 and 17.6 respectively, df = 2,41, P < 0.0005, with no significant interaction of strain with dose for either measure. It should be noted that the enzymatic activities were measured on a protein basis. Because of the relatively low protein content found in the injected CP of Wistar rats, enzyme differences between Sprague-Dawley and Wistar rats would have been even more marked if the data were expressed relative to tissue weight, rather than protein content. In fact, no reliable differences in tissue weight were found between control and injected CP in either strain. It is apparent that in addition to the methods used to inject K A 7 into the neostriatum, genetic differences also play a role on the magnitude of the resulting biochemical alterations. This genetic factor should be carefully considered in quantitative comparisons of the effects of K A injections reported by different laboratories. The present finding of genetic influences on the neurodegenerative effects of K A extend the previously reported biochemicap,6,7,12,15, histological 2,3,5,16, pharmacological 5,13, and behavioral3,11,1~ similarities between striatal lesions resulting from K A in animals and those resulting from Huntington's disease in man 1. The present data show that the neostriatum of Wistar rats is more sensitive to the neurotoxic effects of K A than that of Sprague-Dawley rats. On the other hand, Chester-Beatty hooded rats did not substantially differ in this respect, inspite of previous and present observations indicating especially marked behavioral and regulatory disorders, and an unusually high mortality rate in hooded rats after K A intrastriatal injections. The mechanisms responsible for the latter effects in ChesterBeatty hooded rats remain to be studied. Strain effects were also found on the enzymatic activities of the non-injected neostriatum. It is unlikely that these differences resulted from spread of K A to the control neostriatum of the Sprague-Dawley and the Chester-Beatty rats, since there was no significant effect of dose on the enzymatic activities. To our knowledge this is the first report of strain differences in neostriatal CAT and G A D activities. Whether these differences are related to the effect of strain on the neurotoxic effectiveness of K A remains to be determined. This work was supported by grants from the Medical Research Council of Canada and the Huntington's Chorea Foundation. We wish to express our sincerest thanks to K. Singh, U. Scherer and D. Money for excellent technical assistance, and Drs. M. E. Corcoran and H. C. Fibiger for helpful comments during the course of this study.
1 Coyle, J. T., Schwarcz, R., Bennett, J. P. and Campochiaro, P., Clinical, neuropathologic and pharmacologic aspects of Huntington's disease: correlates with a new animal model, Prog. Neuro-Psychopharmacol., I (1977) 13-30. 2 Coyle, J. T., Molliver, M. E. and Kuhar, M. J., In situ injection of kainic acid: a new method for selectively lesioning neuronal cell bodies while sparing axons of passage, J. comp. NeuroL, 180 (1978) 301-324. 3 Divac, I., Markowitsch, H. J. and Pritzel, M., Behavioral and anatomical consequences of small intrastriatal injections of kainic acid in the rat, Brain Research, 151 (1978) 523-532.
435 4 Lowry, O. H., Rosebrough, N. J., Farr, A. L. and Randall, R. J., Protein measurement with the Folin phenol reagent, J. biol. Chem., 193 (1951) 265-275. 5 Mason, S. T., Sanberg, P. R. and Fibiger, H. C., Kainic acid lesions of the striatum dissociate amphetamine and apomorphine stereotypy: similarities to Huntington's chorea, Science, 201 (1978) 352-355. 6 McGeer, E. G., and McGeer, P. L., Duplication of biochemical changes of Huntington's chorea by intrastriatal injections of glutamic and kainic acids, Nature (Lond.), 263 (1976) 517-519. 7 McGeer, E. G. and McGeer, P. L., Some factors influencing the neurotoxicity of intrastriatal injections of kainic acid, Neurochem. Res., 3 (1978) 501-517. 8 McGeer, P. L. and McGeer, E. G., Enzymes associated with the metabolism of catecholamines, acetylcholine and GABA in human controls and patients with Parkinson's disease and Huntington's chorea, J. Neurochem., 26 (1976) 65-76. 9 McGeer, P. L., McGeer, E. G., Scherer, U. and Singh, K., A glutamatergic cortico-striatal path? Brain Research, 128 (1977) 369-373. 10 Olney, J. W:, Sharpe, L. G. and de Gubareff, T., Excitotoxic amino acids, Neurosci. Abstr., 1 (1975) 371. 11 Pisa, M., Sanberg, P. R. and Fibiger, H. C., Learning impairments in rats with experimental degeneration of the neostriatal neuropil, Neurosci. Abstr., 4 (1978) 48. 12 Sanberg, P. R., Lehmann, J. and Fibiger, H. C., Impaired learning and memory after kainic acid lesions of the striatum: a behavioral model of Huntington's disease, Brain Resecrch, 149 (1978) 546-551. 13 Sanberg, P. R.,, Lehmann, J. and Fibiger, H. C., The sedative action of apomorphine and an animal model of Huntington's disease, Arch. Neurol (Chic.), in press. 14 Scheff6, H., The Analysis of Variance, John Wiley, New York, 1959. 15 Schwarcz, R. and Coyle, J. T., Striatal lesions with kainic acid: neurochemical characteristics, Brain Research, 127 (1977) 235-249. 16 Wuerthele, S. M., Lovell, K. L., Jones, M. Z. and Moore, K. E., A histological study of kainic acid-induced lesions in rat brain, Brain Research, 149 (1978) 489--497
431
© Elsevier/North-Holland Biomedical Press
Strain differences and kainic acid neurotoxicity
PAUL R. SANBERG, MICHELE PISA and EDITH G. McGEER Kinsmen Laboratory of Neurological Research, Department of Psychiatry, University of British Columbia, Vancouver, B.C. V6T IW5 (Canada)
(Accepted December 21st, 1978)
Since Olney's original report 10 on the specific toxic effects of kainic acid (KA) on neuronal perikarya, several studies have been conducted in different laboratories on the anatomical1-3,5,16 and biochemical1,6,7,12,15 effects of KA injections into the neostriatum (CP). Much of the variability in the magnitude of the resulting lesions can be undoubtedly attributed to the use of different doses, volumes and rates of injections of the KA solution. It has in fact been shown that each of these injection parameters can remarkably affect the extent of neuronal loss in the CP 7. Recent observations, however, suggested that a genetic factor may also influence the neurotoxic effectiveness of KA. Thus, it was noted that identical neostriatal injections resulted in a more severe aphagia and adipsia, and in a higher mortality rate in hooded than in Wistar rats (Sanberg and Corcoran, unpublished data). It also appeared that different litters of rats of the same Wistar strain might show considerable differences in the extent of CP damage after identical injections of KA (Pisa, Sanberg and Fibiger, unpublished data). Also, investigators using Wistar rats3, 5-7 have reported CP lesions of similar extent to that found by other investigators using Sprague-Dawley rats 1,2, 15,16, even though widely different injection parameters were used. Here we report biochemical data indicating that strain differences in sensitivity to KA are indeed another factor to be considered in comparing data of various laboratories. Male Wistar albino rats (Woodlyn Farms, Guelph, Ontario), SpragueDawley albino rats (Biobreeding Labs, Ottawa, Ontario), and Chester-Beatty hooded rats (Biobreeding Labs, Ottawa, Ontario) weighing approximately 300 g at the time of surgery were included in the study. After anesthesia with pentobarbital (50 mg/kg i.p.) the rats were given unilateral intrastriatal injections of either 2.5 or 5.0 nmol of KA (Sigma Chemical Co.) dissolved in 1.0 #1 of phosphate buffered saline solution, pH 7.2, through a 34 gauge cannula over a 5-min period. The cannula was left in place for a further 1 min to allow diffusion of the drug solution. With the incisor bar at 4.2 mm below the interaural line, coordinates used were AP +9.6 and DV +4.5, with reference to the interaural line; and ML --2.8, with reference to the sagittal suture. The rats were operated in two series and an interval of either I0 or 18 days separated surgery from sacrifice. Rats were killed by cervical fracture, and the CP was bilaterally dissected, weighed, and homogenized in 10 vol of either 0.25 M or (for uptake assays)
432 TABLE I
Neurochemical parameters in the control, noninjected neostriatum of rats of 3 different strains The contralateral side was injected with either 2.5 or 5 nmol of kainic acid at least 10 days prior to sacrifice. Values represent means ± S,E.M. Protein content was measured on a wet tissue weight basis. Enzymes and glutamate uptake were measured on a protein content basis.
Dose
Strain Sprague-Dawley (n)
Wistar (n)
Chester Beatty (n)
10.54 31.28 12.89 3012
i 0.20 ± 0.36 -4- 0.59 5- 204
(10) (10) (10) (5)
10.52 34.96 14.68 2999
± i 5:k
0.28 1.66 0.26 202
(10) (10) (10) (5)
10.25 5- 0.26 35.21 5- 0.96 13.58 5- 0.24 --
(5) (5) (5)
9.85 31.33 13.48 2761
5± ± ±
(8) (8) (8) (3)
10.52 32.99 14.83 3067
5± :k ~
0.42 1.45 0.36 154
(10) (10) (10) (5)
10.68 4- 0.30 34.66 ± 0.93 13.46 5- 0.36 --
(4) (4) (4)
2.5 nmole KA Protein mg/g CAT*,** GAD*,** Glutamate uptake**
5.0 nmole K,4 Protein mg/g CAT*,** GAD*,** Glutamate uptake**
0.35 0.57 0.41 152
* Significant strain differences, P < 0.01. ** in/Lmol'h-l'100 mg.protein-I.
0.32 M of sucrose. The activities of the two neurotransmitter synthesizing enzymes choline acetyltransferase (CAT) and glutamic acid decarboxylase (GAD), commonly considered as functional indicators of cholinergic and GABAergic neurons respectively, were measured by previously reported radioenzymatic assay methods s. Protein content was measured according to Lowry et al ~. In the rats of the second series high affinity glutamate uptake, a functional indicator of presumably glutamatergic corticostriatal afferent terminals 9, was also measured as previously reported 9, using samples of a homogenate of the P2 pellet fraction and sodium-free blanks. Since the trend of the results was similar in both series, the data of the two series combined are reported. For rats of the Chester-Beatty hooded strain only data from the first series are available, since 8 out of 10 rats operated in the second series died within a few days after surgery. Data were analyzed with two-way analyses of variance, with Strains and Dose as main Factors, using an unweighted means solution. Multiple comparisons between strains were conducted using Scheff6's F test. Since this test is more rigorous than other methods of multiple comparisons a 10 ~ significance level was accepted 14. Data for non-injected CP are shown in Table I. There were no significant effects of strains on either protein content, F < 1, or glutamate uptake, F < 1. However, rats of different strains significantly differed in both CAT and G A D activities, F = 4.4 and 8.6 respectively, df = 2,44; P < 0.01. Multiple comparisons between strains revealed that Sprague-Dawley rats had significantly less CAT activity than either Wistar or Chester-Beatty rats. Also, both Sprague-Dawley and Chester-Beatty rats had less G A D activity than Wistar rats. Neither the main effect of dose nor the interaction term were significant for any of the indices measured, F's < 1.
433 TABLE II Neurochemical parameters in the kahlic acid injected neostriatum of rats of 3 different strains
Values are expressed as mean percentages ± S.E.M. of the related values in the contralateral noninjected neostriatum. Dose
Strain Sprague-Dawley (n)
Wistar (n)
Chester-Beatty (n)
2.5 nmole KA
Protein mg/g CAT**,*** GAD**,*** Glutamate uptake
101.8 ± 3.6 73.9 ± 2.9 75.9 zk 3.1 88.2 4, 6.2
(10) (10) (10) (5)
97.6 4. 59.3 4, 65.1 4. 102.0 4,
(8) (8) (8) (3)
96.8 ± 4.0 (10) 59.7 ± 2.1 (10) 61.4 4. 2.3 (10) 95.8 4, 7.83 (5)
101.7 ± 5.5 (5) 54.6 4. 1.9 (5) 57.7 4. 1.6 (5) --
5.0 nmole KA
Protein mg/g* CAT**,*** GAD**,*** Glutamate uptake
4.9 3.7 3.2 2.2
85.9 4- 3.5 40.2 4, 3.6 47.9 4, 3.3 103.3 4. 1.8
(10) (10) (10) (5)
104.7 4, 1.0 (4) 47.9 4- 1.3 (4) 51.8 4. 3.3 (4) --
* significant strain differences, P < 0.05. significant strain differences, P < 0.005. *** significantly different from lower dose, P < 0.005. **
Table II shows data in the injected CP, expressed as percentages o f the related values in the noninjected CP. Analysis of variance o f the protein data revealed a significant effect o f strain, F = 3.8; df = 2,41; p < 0.05. Multiple comparisons between strains indicated a significantly greater decrease of protein content in the Wistar than in the Chester-Beatty rats. N o other comparison attained the 1 0 ~ level of significance. Both the main effect o f dose and the interaction term were not significant, F ' s < 1. There were no significant differences in protein content between the injected CP and their corresponding control CP in either strain. The difference in the injected CP protein content between the Wistar strain and the Chester-Beatty strain rats m a y reflect greater edema in the injected CP o f the Wistar rats during the acute stages following the K A injections. There were no reliable differences between Sprague-Dawley and Wistar rats in glutamate uptake in the injected CP, F < 1, at either dose, F = 3.07; df = 1,14. Indeed, in agreement with previous findings 7, K A injections did not affect glutamate uptake, as shown by the lack o f substantial differences between control and injected CP in uptake values. As expected1,5-7,12,15, the rats o f all groups revealed a marked decrease in both C A T and G A D activities in the injected CP. The main finding was a significant effect o f strain on the decrease o f b o t h C A T and G A D activities, F = 18.9 and 18.7 respectively, df = 2,41 ; P < 0.0005. Multiple comparisons between strains indicated that this effect mainly resulted f r o m a significantly smaller decrease of both enzymes in S p r a g u e - D a w l e y rats c o m p a r e d with rats o f the other two strains. Both C A T and G A D decreased significantly more in the rats treated with the higher dose o f K A ,
434 F = 32.7 and 17.6 respectively, df = 2,41, P < 0.0005, with no significant interaction of strain with dose for either measure. It should be noted that the enzymatic activities were measured on a protein basis. Because of the relatively low protein content found in the injected CP of Wistar rats, enzyme differences between Sprague-Dawley and Wistar rats would have been even more marked if the data were expressed relative to tissue weight, rather than protein content. In fact, no reliable differences in tissue weight were found between control and injected CP in either strain. It is apparent that in addition to the methods used to inject K A 7 into the neostriatum, genetic differences also play a role on the magnitude of the resulting biochemical alterations. This genetic factor should be carefully considered in quantitative comparisons of the effects of K A injections reported by different laboratories. The present finding of genetic influences on the neurodegenerative effects of K A extend the previously reported biochemicap,6,7,12,15, histological 2,3,5,16, pharmacological 5,13, and behavioral3,11,1~ similarities between striatal lesions resulting from K A in animals and those resulting from Huntington's disease in man 1. The present data show that the neostriatum of Wistar rats is more sensitive to the neurotoxic effects of K A than that of Sprague-Dawley rats. On the other hand, Chester-Beatty hooded rats did not substantially differ in this respect, inspite of previous and present observations indicating especially marked behavioral and regulatory disorders, and an unusually high mortality rate in hooded rats after K A intrastriatal injections. The mechanisms responsible for the latter effects in ChesterBeatty hooded rats remain to be studied. Strain effects were also found on the enzymatic activities of the non-injected neostriatum. It is unlikely that these differences resulted from spread of K A to the control neostriatum of the Sprague-Dawley and the Chester-Beatty rats, since there was no significant effect of dose on the enzymatic activities. To our knowledge this is the first report of strain differences in neostriatal CAT and G A D activities. Whether these differences are related to the effect of strain on the neurotoxic effectiveness of K A remains to be determined. This work was supported by grants from the Medical Research Council of Canada and the Huntington's Chorea Foundation. We wish to express our sincerest thanks to K. Singh, U. Scherer and D. Money for excellent technical assistance, and Drs. M. E. Corcoran and H. C. Fibiger for helpful comments during the course of this study.
1 Coyle, J. T., Schwarcz, R., Bennett, J. P. and Campochiaro, P., Clinical, neuropathologic and pharmacologic aspects of Huntington's disease: correlates with a new animal model, Prog. Neuro-Psychopharmacol., I (1977) 13-30. 2 Coyle, J. T., Molliver, M. E. and Kuhar, M. J., In situ injection of kainic acid: a new method for selectively lesioning neuronal cell bodies while sparing axons of passage, J. comp. NeuroL, 180 (1978) 301-324. 3 Divac, I., Markowitsch, H. J. and Pritzel, M., Behavioral and anatomical consequences of small intrastriatal injections of kainic acid in the rat, Brain Research, 151 (1978) 523-532.
435 4 Lowry, O. H., Rosebrough, N. J., Farr, A. L. and Randall, R. J., Protein measurement with the Folin phenol reagent, J. biol. Chem., 193 (1951) 265-275. 5 Mason, S. T., Sanberg, P. R. and Fibiger, H. C., Kainic acid lesions of the striatum dissociate amphetamine and apomorphine stereotypy: similarities to Huntington's chorea, Science, 201 (1978) 352-355. 6 McGeer, E. G., and McGeer, P. L., Duplication of biochemical changes of Huntington's chorea by intrastriatal injections of glutamic and kainic acids, Nature (Lond.), 263 (1976) 517-519. 7 McGeer, E. G. and McGeer, P. L., Some factors influencing the neurotoxicity of intrastriatal injections of kainic acid, Neurochem. Res., 3 (1978) 501-517. 8 McGeer, P. L. and McGeer, E. G., Enzymes associated with the metabolism of catecholamines, acetylcholine and GABA in human controls and patients with Parkinson's disease and Huntington's chorea, J. Neurochem., 26 (1976) 65-76. 9 McGeer, P. L., McGeer, E. G., Scherer, U. and Singh, K., A glutamatergic cortico-striatal path? Brain Research, 128 (1977) 369-373. 10 Olney, J. W:, Sharpe, L. G. and de Gubareff, T., Excitotoxic amino acids, Neurosci. Abstr., 1 (1975) 371. 11 Pisa, M., Sanberg, P. R. and Fibiger, H. C., Learning impairments in rats with experimental degeneration of the neostriatal neuropil, Neurosci. Abstr., 4 (1978) 48. 12 Sanberg, P. R., Lehmann, J. and Fibiger, H. C., Impaired learning and memory after kainic acid lesions of the striatum: a behavioral model of Huntington's disease, Brain Resecrch, 149 (1978) 546-551. 13 Sanberg, P. R.,, Lehmann, J. and Fibiger, H. C., The sedative action of apomorphine and an animal model of Huntington's disease, Arch. Neurol (Chic.), in press. 14 Scheff6, H., The Analysis of Variance, John Wiley, New York, 1959. 15 Schwarcz, R. and Coyle, J. T., Striatal lesions with kainic acid: neurochemical characteristics, Brain Research, 127 (1977) 235-249. 16 Wuerthele, S. M., Lovell, K. L., Jones, M. Z. and Moore, K. E., A histological study of kainic acid-induced lesions in rat brain, Brain Research, 149 (1978) 489--497