Brain Research Bulletin, Vol. 24, pp. 839-842. 0 Pergamon Press plc, 1990. Printed in the U.S.A.
0361-9230/90 $3.00 + .OO
RAPID COMMUNICATION
Effects of Quisqualic Acid Nucleus Basalis Lesioning on Cortical EEG, Passive Avoidance and Water Maze Performance PAAVO RIEKKINEN, JR. ,*t’ JOUNI SIRVIij,* TUULA HANNILA,* RIITTA MIETTINEN*I_ AND PAAVO RIEKKINEN* Departments of *Neurology and ?Pathology, University of Kuopio, Kuopio, Finland Received 20 February 1990
RIEKKINEN, P., JR., J. SIRVIO, T. HANNILA, R. MIETTINEN AND P. RIEKKINEN. Effects ofquisquak acid nucleus basalis lesioning on corfical EEG, passive avoidance and water maze performance. BRAIN RES BULL 24(6) 839-842, 1990.-The study examines the effects of unilateral quisqualic acid nucleus basalis (NB) lesioning on cortical EEG and learning behavior. Lesions produced both gliosis in the ventral pallidum and a marked reduction in the cortical ChAT activity. Normal cortical EEG activity was abolished on the side of NB lesion, i.e., slow wave activity and the incidence of high voltage spindles was higher on the side of lesion compared with the control side. NB lesioning impaired passive avoidance retention, but not spatial learning ability. These results suggest that EEG and passive avoidance deficits induced by NB quisqualic acid lesion may result from the damage specifically to cholinergic neurons. Thus, the restoration of EEG and passive avoidance performance defects in quisqualic-lesioned rats may be used as an index of the efficacy of the cholinergic replacement therapies. Nucleus basalis
Spectral powers
High voltage spindles
Passive avoidance
to Paavo Riekkinen,
Quisqualic
acid
ing nuclei than ibotenic acid at doses that produces the same reduction in cortical choline acetyltransferase (ChAT) activity (5). Moreover, among the proliferated glial elements in the quisq&ate-infused area, some small noncholinergic neurons were spared (13). The chemical identity or connective patterns of these neurons is at present unknown. Also, recent studies have revealed that learning deficits induced by quisqualic acid NB lesion are much smaller than those induced by ibotenic acid NB lesion (5,13). Thus, it is reasonable to believe that the ibotenic acid-induced leaming deficits, although associated with cholinergic neuron loss, may partially result from nonspecific subcortical damage in the basal forebrain (5, 12, 13). The results of the previous studies which determine the role of cholinergic NB in the regulation of neocortical EEG are controversial. Electrolytic NB lesions produced a depression of EEG total amplitude whereas kainic acid NB lesioning increased EEG slow waves during waking-immobility (9,15). However, both the destruction of fibers of passage induced by electrolytic lesioning and large subcortical damage in surrounding nuclei induced by the
central nervous system cholinergic transmission has been proposed to be involved significantly in learning behavior and regulation of cortical electrical activity (3, 4, 11, 12). Secondly, the memory deficits and EEG slowing found in patients with Alzheimer’s disease may be attributable to degeneration of the nucleus basalis (NB) cholinergic neurons (2,14). Thus, animal models of AD have concentrated on the mnemonic and neurophysiological consequences of destruction of the NB, the major source of extrinsic cholinergic innervation of the neocortex and reticular nucleus of the thalamus (1,8). Several of the studies have used intracerebral ibotenic acid infusions to produce both a cholinergic cell loss and deficits of learning and memory. However, the specificity of this preparation as a model for experimental cholinergic denervation is debatable. Ibotenic acid infusions destroy magnocellular cholinergic cells as well as noncholinergic neurons located in the ventral pallidum, and also produce large nonspecific subcortical damage in adjacent structures (5). Quisqualic acid, another exicotoxin, infused into the ventral pallidum induces less nonspecific damage in surroundTHE
‘Requests for reprints should be addressed Finland.
Spatial learning
Jr., Department
839
of Neurology,
University
of Kuopio,
P.O.B.
6, SF-7021 1, Kuopio,
RIEKKINEN
840
ET AL..
”
NBL
NBC
C
NBC
C
60
8OT 2
k-
160
160 I
2a40 7 20 0 Ir
NBL
NBC
C
NBL
FIG. 2. Frontal waking-immobility-related EEG amplitude values (FV) recorded ipsilaterally to the intracerebral infusions. The values are expressed as mean?S.D. Frequency bands: 1.0-4 Hz (delta), 4-8 Hz (theta), 8-12 Hz (alpha), 12-20 Hz (beta). See group abbreviations from Table 2. *pO.O5 in all comparisons). Thus, the data obtained during the first recording session was used in all statistical analysis. Figure 2 shows frontal EEG values recorded from the side of brain ipsilateral to the intracerebral infusions during wakingimmobility. Movement and waking-immobility-related EEG recordings show that NB lesioning increased EEG slow waves [delta, F(2,33) = 3.2, pcO.05; Duncan, pO.O5 (Fig. 3), path length, F(42,196)=0.5, p>O.O5 (data not shown) or swim speed, F(42,196) =0.8, p>O.O5 (data not shown). Furthermore, Duncan’s test revealed no significant group differences either in these
250 ~200 T 150
TABLE 2 THE TOTAL DURATION (SECOND) OF HIGH VOLTAGE SPINDLES (HVS) Q)
Group
Total Duration
NB NBC C
145 2 36* 23 ” 13 18 ? 14
Values are expressed as mean f S.D. Abbreviations: NB = nucleus basalis-lesioned, NBC = nucleus basalis control-lesioned, C = controls. *pO.O5] or number of reentries [F(2,16)=0.4, pBO.05, Duncan, p>O.O5] during the PA training trial (Table 3). However, during the retention trial a significant main group effect on the entry latency was found, F(2,16) = 3.1, pcO.05 (Fig. 4). NB-lesioned rats were impaired (Duncan, pcO.05) compared with the other groups.
DISCUSSION The present results demonstrate that passive avoidance but not water maze acquisition is impaired following unilateral quisqualate NB lesioning. Moreover, cortical EEG slow wave activity and HVSs were increased on the side of lesion. Furthermore, no recovery of EEG activity occurred during the course of experiment (25 days). Our results further support the fact that NB cortical cholinergic system is not significantly involved in spatial navigation (5, 12, 13). It has been proposed that the learning deficits induced by ibotenic acid NB lesioning are not as a consequence of the cholinergic deafferentation of the cortex, but may result from a damage to frontostriatal system, the output of which courses
ET AL.
through the ventral and dorsal globus pallidus (13). Since previous studies have shown that the globus pallidus is damaged by ibotenate infusions, the spatial navigation impairments may result from the accidental lesioning of the frontostriatal system (5, 12, 13). Another possibility is that ibotenate-induced behavioral deficits result from damage to some other neurochemical system in the NB which is spared following quisqualate lesioning (13). We are presently investigating that possibility. Our result further supports the importance of the NB neurons in regulating the passive avoidance acquisition. Since scopolamine injections and cortical lesioning result in similar memory deficits (6). the passive avoidance impairment observed in the present study may result from the loss of cortical cholinergic fibers. Interestingly, the passive avoidance deficits were associated with neocortical electrical arousal deficits (increase of slow waves and HVSs), which further supports the importance of cholinergic deafferentation of the cortex in avoidance performance impairments. However, the contribution from noncholinergic NB neurons damaged to the passive avoidance impairments cannot be excluded. Our neurophysiological results demonstrating EEG slowing induced by restricted quisqualic acid NB lesioning further support the importance of the NB cholinergic neurons in direct cortical activation and suppression of the rhythmic activity of the nucleus reticularis thalamus. Previous studies support our conclusion. It has been shown that scopolamine, a muscarinic antagonist, produced smaller EEG change in ibotenate NB-lesioned rats than in controls (3). Moreover, the EEG slow wave activity correlated with the cortical ChAT activity in NB-lesioned rats. In our recent study we have shown that NB lesioning-induced EEG changes are partially reversed by either muscarinic agonist or cholinesterase inhibitor (10). In conclusion, the present results show for the first time that quisqualic acid NB lesioning abolishes both desynchronized EEG activity and impairs passive avoidance learning. Thus, our results suggest that these deficits may result from the loss of cholinergic neurons in the NB and furthermore that in future pharmacological studies quisqualate NB lesioning may be a suitable preparation for studying the effectiveness of cholinergic replacement therapies.
REFERENCES 1. Armstrong, D. M.; Saper, C. B.; Levey, A. I. Distribution of cholinergic neurons in rat brain: demonstrated by the immunohistochemical localisation of choline acetyltransferase. J. Comp. Neurol. 216:53-68; 1983. 2. Bartus, R. T.; Dean, R. L.; Beer, B.; Lippa, A. S. The cholinergic hypothesis of geriatric memory dysfunction. Science 217408417; 1982. 3. Buzsaki, G.; Bickford, R. G.; Ponomareff, Cl.; Thai, L. J.; Mandel, R.; Gage, F. H. Nucleus basalis and thalamic control of neocortical activity in the freely moving rat. J. Neurosci. 84007-4026; 1988. 4. Dunnett, S. B.; Low, W. C.; Iversen, S. D.; Stenevi, U.; Bjorklund, A. Septal transplants restore maze learning in rats with fomix-fimbria lesions. Brain Res. 251:335-348; 1982. 5. Dunnett, S. B.; Whishaw, I. Q.; Jones, G. H.; Bunch, S. T. Behavioural, biochemical and histochemical effects of different neurotoxic amino acids injected into nucleus basalis magnocellularis of rats. Neuroscience 20:653-669; 1987. 6. Flood, J.; Cherkin, A. Scopolamine effects on memory retention on mice: A model of dementia? Behav. Neural Biol. 45:169-184; 1986. 7. Fonnum, F. A rapid radiochemical method of the determination of choline acetyltransferase. J. Neurochem. 24:407X)9; 1975. 8. Levey, A. I.; Hallonger, A. E.; Wainer, B. H. Cholinergic nucleus basalis neurons may influence the cortex via the thalamus. Neurosci. Lea. 74:7-13; 1987. 9. Lo Conte, G.; Casamenti, F.; Bigl, V.; Milaneschi, E.; Pepeu, G. Effects of magnocellular forebrain nuclei lesions on acetylcholine output from the cerebral cortex, electmcorticogram and behavior.
Arch. Ital. Biol. 120:17&188; 1982. 10. Riekkinen, P., Jr.; JXkalB, P.; Sirvio, J.; Riekkinen, P. Effects of THA on scopolamine and nucleus basalis lesioning induced EEG slowing. Submitted. 11. Riekkinen, P., Jr.; Sin%, J.; Riekkinen, P. J. Relationship between the cortical ChAT content and EEG delta activity. Neurosci. Res.; in press. 12. Riekkinen, P., Jr.; Sirvio, J.; Riekkinen, P. Similar memory impairments found in medial septal-vertical diagonal band of Broca and nucleus basalis lesioned rats: are memory defects induced by nucleus basalis lesions related to the degree of non-specific subcortical cell loss? Behav. Brain Res. 37:81-88; 1990. 13. Robbins, T. W.; Eve&t, B. J.; Marston, H. M.; Wilkinson, J.; Jones, G. H.; Page, K. J. Comparative effects of ibotenic acid and quisqualic acid-induced lesions of the substantia innominata on attentional function in the rat: further implications for the role of the cholinergic neurons of the nucleus basalis in cognitive processes. Behav. Brain Res. 35:221-240; 1989. 14. Soininen, H.; Partanen, J.; Laulumaa, V.; HelkalaE.-L.; Laakso, M.; Riekkinen, P. J. Longitudinal EEG spectral analysis in early stage of Alzheimer’s disease. Electroencephalogr. Clin. Neurophysiol. 72: 290-297; 1989. 15. Stewart, D. J.; MacFabe, D. F.; Vanderwolf, C. H. Cholinergic activation of the electrocorticogram: Role of substantia innominata and effects of atropine and quinuclidinyl benzylate. Brain Res. 322:219-232; 1984.
0361-9230/90 $3.00 + .OO
RAPID COMMUNICATION
Effects of Quisqualic Acid Nucleus Basalis Lesioning on Cortical EEG, Passive Avoidance and Water Maze Performance PAAVO RIEKKINEN, JR. ,*t’ JOUNI SIRVIij,* TUULA HANNILA,* RIITTA MIETTINEN*I_ AND PAAVO RIEKKINEN* Departments of *Neurology and ?Pathology, University of Kuopio, Kuopio, Finland Received 20 February 1990
RIEKKINEN, P., JR., J. SIRVIO, T. HANNILA, R. MIETTINEN AND P. RIEKKINEN. Effects ofquisquak acid nucleus basalis lesioning on corfical EEG, passive avoidance and water maze performance. BRAIN RES BULL 24(6) 839-842, 1990.-The study examines the effects of unilateral quisqualic acid nucleus basalis (NB) lesioning on cortical EEG and learning behavior. Lesions produced both gliosis in the ventral pallidum and a marked reduction in the cortical ChAT activity. Normal cortical EEG activity was abolished on the side of NB lesion, i.e., slow wave activity and the incidence of high voltage spindles was higher on the side of lesion compared with the control side. NB lesioning impaired passive avoidance retention, but not spatial learning ability. These results suggest that EEG and passive avoidance deficits induced by NB quisqualic acid lesion may result from the damage specifically to cholinergic neurons. Thus, the restoration of EEG and passive avoidance performance defects in quisqualic-lesioned rats may be used as an index of the efficacy of the cholinergic replacement therapies. Nucleus basalis
Spectral powers
High voltage spindles
Passive avoidance
to Paavo Riekkinen,
Quisqualic
acid
ing nuclei than ibotenic acid at doses that produces the same reduction in cortical choline acetyltransferase (ChAT) activity (5). Moreover, among the proliferated glial elements in the quisq&ate-infused area, some small noncholinergic neurons were spared (13). The chemical identity or connective patterns of these neurons is at present unknown. Also, recent studies have revealed that learning deficits induced by quisqualic acid NB lesion are much smaller than those induced by ibotenic acid NB lesion (5,13). Thus, it is reasonable to believe that the ibotenic acid-induced leaming deficits, although associated with cholinergic neuron loss, may partially result from nonspecific subcortical damage in the basal forebrain (5, 12, 13). The results of the previous studies which determine the role of cholinergic NB in the regulation of neocortical EEG are controversial. Electrolytic NB lesions produced a depression of EEG total amplitude whereas kainic acid NB lesioning increased EEG slow waves during waking-immobility (9,15). However, both the destruction of fibers of passage induced by electrolytic lesioning and large subcortical damage in surrounding nuclei induced by the
central nervous system cholinergic transmission has been proposed to be involved significantly in learning behavior and regulation of cortical electrical activity (3, 4, 11, 12). Secondly, the memory deficits and EEG slowing found in patients with Alzheimer’s disease may be attributable to degeneration of the nucleus basalis (NB) cholinergic neurons (2,14). Thus, animal models of AD have concentrated on the mnemonic and neurophysiological consequences of destruction of the NB, the major source of extrinsic cholinergic innervation of the neocortex and reticular nucleus of the thalamus (1,8). Several of the studies have used intracerebral ibotenic acid infusions to produce both a cholinergic cell loss and deficits of learning and memory. However, the specificity of this preparation as a model for experimental cholinergic denervation is debatable. Ibotenic acid infusions destroy magnocellular cholinergic cells as well as noncholinergic neurons located in the ventral pallidum, and also produce large nonspecific subcortical damage in adjacent structures (5). Quisqualic acid, another exicotoxin, infused into the ventral pallidum induces less nonspecific damage in surroundTHE
‘Requests for reprints should be addressed Finland.
Spatial learning
Jr., Department
839
of Neurology,
University
of Kuopio,
P.O.B.
6, SF-7021 1, Kuopio,
RIEKKINEN
840
ET AL..
”
NBL
NBC
C
NBC
C
60
8OT 2
k-
160
160 I
2a40 7 20 0 Ir
NBL
NBC
C
NBL
FIG. 2. Frontal waking-immobility-related EEG amplitude values (FV) recorded ipsilaterally to the intracerebral infusions. The values are expressed as mean?S.D. Frequency bands: 1.0-4 Hz (delta), 4-8 Hz (theta), 8-12 Hz (alpha), 12-20 Hz (beta). See group abbreviations from Table 2. *pO.O5 in all comparisons). Thus, the data obtained during the first recording session was used in all statistical analysis. Figure 2 shows frontal EEG values recorded from the side of brain ipsilateral to the intracerebral infusions during wakingimmobility. Movement and waking-immobility-related EEG recordings show that NB lesioning increased EEG slow waves [delta, F(2,33) = 3.2, pcO.05; Duncan, pO.O5 (Fig. 3), path length, F(42,196)=0.5, p>O.O5 (data not shown) or swim speed, F(42,196) =0.8, p>O.O5 (data not shown). Furthermore, Duncan’s test revealed no significant group differences either in these
250 ~200 T 150
TABLE 2 THE TOTAL DURATION (SECOND) OF HIGH VOLTAGE SPINDLES (HVS) Q)
Group
Total Duration
NB NBC C
145 2 36* 23 ” 13 18 ? 14
Values are expressed as mean f S.D. Abbreviations: NB = nucleus basalis-lesioned, NBC = nucleus basalis control-lesioned, C = controls. *pO.O5] or number of reentries [F(2,16)=0.4, pBO.05, Duncan, p>O.O5] during the PA training trial (Table 3). However, during the retention trial a significant main group effect on the entry latency was found, F(2,16) = 3.1, pcO.05 (Fig. 4). NB-lesioned rats were impaired (Duncan, pcO.05) compared with the other groups.
DISCUSSION The present results demonstrate that passive avoidance but not water maze acquisition is impaired following unilateral quisqualate NB lesioning. Moreover, cortical EEG slow wave activity and HVSs were increased on the side of lesion. Furthermore, no recovery of EEG activity occurred during the course of experiment (25 days). Our results further support the fact that NB cortical cholinergic system is not significantly involved in spatial navigation (5, 12, 13). It has been proposed that the learning deficits induced by ibotenic acid NB lesioning are not as a consequence of the cholinergic deafferentation of the cortex, but may result from a damage to frontostriatal system, the output of which courses
ET AL.
through the ventral and dorsal globus pallidus (13). Since previous studies have shown that the globus pallidus is damaged by ibotenate infusions, the spatial navigation impairments may result from the accidental lesioning of the frontostriatal system (5, 12, 13). Another possibility is that ibotenate-induced behavioral deficits result from damage to some other neurochemical system in the NB which is spared following quisqualate lesioning (13). We are presently investigating that possibility. Our result further supports the importance of the NB neurons in regulating the passive avoidance acquisition. Since scopolamine injections and cortical lesioning result in similar memory deficits (6). the passive avoidance impairment observed in the present study may result from the loss of cortical cholinergic fibers. Interestingly, the passive avoidance deficits were associated with neocortical electrical arousal deficits (increase of slow waves and HVSs), which further supports the importance of cholinergic deafferentation of the cortex in avoidance performance impairments. However, the contribution from noncholinergic NB neurons damaged to the passive avoidance impairments cannot be excluded. Our neurophysiological results demonstrating EEG slowing induced by restricted quisqualic acid NB lesioning further support the importance of the NB cholinergic neurons in direct cortical activation and suppression of the rhythmic activity of the nucleus reticularis thalamus. Previous studies support our conclusion. It has been shown that scopolamine, a muscarinic antagonist, produced smaller EEG change in ibotenate NB-lesioned rats than in controls (3). Moreover, the EEG slow wave activity correlated with the cortical ChAT activity in NB-lesioned rats. In our recent study we have shown that NB lesioning-induced EEG changes are partially reversed by either muscarinic agonist or cholinesterase inhibitor (10). In conclusion, the present results show for the first time that quisqualic acid NB lesioning abolishes both desynchronized EEG activity and impairs passive avoidance learning. Thus, our results suggest that these deficits may result from the loss of cholinergic neurons in the NB and furthermore that in future pharmacological studies quisqualate NB lesioning may be a suitable preparation for studying the effectiveness of cholinergic replacement therapies.
REFERENCES 1. Armstrong, D. M.; Saper, C. B.; Levey, A. I. Distribution of cholinergic neurons in rat brain: demonstrated by the immunohistochemical localisation of choline acetyltransferase. J. Comp. Neurol. 216:53-68; 1983. 2. Bartus, R. T.; Dean, R. L.; Beer, B.; Lippa, A. S. The cholinergic hypothesis of geriatric memory dysfunction. Science 217408417; 1982. 3. Buzsaki, G.; Bickford, R. G.; Ponomareff, Cl.; Thai, L. J.; Mandel, R.; Gage, F. H. Nucleus basalis and thalamic control of neocortical activity in the freely moving rat. J. Neurosci. 84007-4026; 1988. 4. Dunnett, S. B.; Low, W. C.; Iversen, S. D.; Stenevi, U.; Bjorklund, A. Septal transplants restore maze learning in rats with fomix-fimbria lesions. Brain Res. 251:335-348; 1982. 5. Dunnett, S. B.; Whishaw, I. Q.; Jones, G. H.; Bunch, S. T. Behavioural, biochemical and histochemical effects of different neurotoxic amino acids injected into nucleus basalis magnocellularis of rats. Neuroscience 20:653-669; 1987. 6. Flood, J.; Cherkin, A. Scopolamine effects on memory retention on mice: A model of dementia? Behav. Neural Biol. 45:169-184; 1986. 7. Fonnum, F. A rapid radiochemical method of the determination of choline acetyltransferase. J. Neurochem. 24:407X)9; 1975. 8. Levey, A. I.; Hallonger, A. E.; Wainer, B. H. Cholinergic nucleus basalis neurons may influence the cortex via the thalamus. Neurosci. Lea. 74:7-13; 1987. 9. Lo Conte, G.; Casamenti, F.; Bigl, V.; Milaneschi, E.; Pepeu, G. Effects of magnocellular forebrain nuclei lesions on acetylcholine output from the cerebral cortex, electmcorticogram and behavior.
Arch. Ital. Biol. 120:17&188; 1982. 10. Riekkinen, P., Jr.; JXkalB, P.; Sirvio, J.; Riekkinen, P. Effects of THA on scopolamine and nucleus basalis lesioning induced EEG slowing. Submitted. 11. Riekkinen, P., Jr.; Sin%, J.; Riekkinen, P. J. Relationship between the cortical ChAT content and EEG delta activity. Neurosci. Res.; in press. 12. Riekkinen, P., Jr.; Sirvio, J.; Riekkinen, P. Similar memory impairments found in medial septal-vertical diagonal band of Broca and nucleus basalis lesioned rats: are memory defects induced by nucleus basalis lesions related to the degree of non-specific subcortical cell loss? Behav. Brain Res. 37:81-88; 1990. 13. Robbins, T. W.; Eve&t, B. J.; Marston, H. M.; Wilkinson, J.; Jones, G. H.; Page, K. J. Comparative effects of ibotenic acid and quisqualic acid-induced lesions of the substantia innominata on attentional function in the rat: further implications for the role of the cholinergic neurons of the nucleus basalis in cognitive processes. Behav. Brain Res. 35:221-240; 1989. 14. Soininen, H.; Partanen, J.; Laulumaa, V.; HelkalaE.-L.; Laakso, M.; Riekkinen, P. J. Longitudinal EEG spectral analysis in early stage of Alzheimer’s disease. Electroencephalogr. Clin. Neurophysiol. 72: 290-297; 1989. 15. Stewart, D. J.; MacFabe, D. F.; Vanderwolf, C. H. Cholinergic activation of the electrocorticogram: Role of substantia innominata and effects of atropine and quinuclidinyl benzylate. Brain Res. 322:219-232; 1984.
