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Serial changes in norepinephrine and dopamine in rat brain after locus coeruleus lesions
198
Brahl Research, 106 (1976) 198 203 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
Serial changes in norepinephrine and dopamine in rat brain after locus coeruleus lesions
W I L L I A M S. WORTH, J A N E T COLLINS, D O U B R A V K A KETT AND JAMES H. AUSTIN
Department of Neurology, University of Colorado Medical Center, Denver, Colo. 80220 (U.S.A.) (Accepted January 5th, 1976)
The locus coeruleus (LC) is the source of one of the major ascending norepinephrine (NE) pathways in the central nervous system 2,4. Each of the paired LC nuclei consists of a discrete collection of cell bodies in the dorsolaterat pontine tegmentum 1~. Axons from these LC neurons ascend, largely uncrossed, via the dorsal bundle to innervate the neo-, paleo-, meso-, and archicortex, and also project to the ipsilateraI cerebellum. The long-range effects that an LC lesion has on catecholamine levels still needs to be determined. Therefore, the goals of this study were: (1) to measure the effects of a unilateral LC lesion on N E and dopamine (DA) levels in pertinent areas of the brain; (2) to determine the serial changes that occur during the three months following such a lesion. The later changes should reflect the degree of compensation afforded by the contralateral LC, the dynamics of catecholamine storage, sprouting and regeneration within this lesioned neuronal pathway 8,18 and possibly other mechanisms still to be discovered. The methods are as follows. Male Sprague-Dawley rats (180-220 g) were housed 6 per cage, receiving standard food pellets and water ad lib. during a 12 h alternating light-dark cycle. Rats were anesthetized with 0.2 ml/kg s.c. of lnovar-Vet (PitmanMoore, Inc.), diluted 1/10. A discrete electrolytic lesion was placed stereotaxically in the left LC at a depth of 7.0 mm. The skull was first tilted forward 20 °, and the burr hole of entry was placed 4.0 mm occipital from the lambda and 1.2 mm lateral to the midline ~,15. The unipolar electrode was 250/tm in diameter, insulated except for 250 # m at the tip. A current of 1.5 mA was applied for 10 sec by a specifically designed direct constant current lesion maker 16. Lesions averaged 500 #m in diameter. To control for non-specific changes secondary to anesthesia or operation, the contralateral (right) side of the same rat was also 'sham' operated, but the electrode stopped in cerebellum at a depth of 5.5 mm and no current was applied. Bilateral 'sham' operations were also performed on some littermate controls (1 and 2 weeks before analysis), but again, no electrolytic lesion was made. 'Normal control' littermates received neither anesthesia nor operation. Rats were decapitated at the same time in the morning 3.7. 14. 21, 28, and 84 days post-operation. The brain was quickly removed and dissected. A thin slab from
199
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/1// Posterior,.////
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Anterior
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-iil
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21
Days Post Lesion
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84
t
0 3 7
14
21
28
84
Days Post Lesion
Fig. t. a, b, c, d: serial changes in NE and DA in rat brain regions after LC lesion. Asterisks represent significant difference from the control.
the LC region, fixed in 10 ~formalin, was stained with the Nissl technique to confirm the lesion histologically. After removing the hypothalamus, the right and left sides of the brain were next rapidly dissected into 4 discrete areas: anterior (0.5)cerebrum, posterior (0.5) cerebrum, cerebellum, and medulla. Wet weight of tissues was determined. Tissues were homogenized in 0.1 N perchloric acid (7.5 ml/g tissue) and centrifuged at 7000 × g for 10 min. Then 0.3 ml of the supernant was assayed in duplicate for N E and D A by a modification of the quantitative labeled O-methylation assay method 3. Histologic confirmation of a discrete lesion involving the LC, as illustrated by Ross and Reis t4 and Kobayashi et al. 7, was the primary basis for including a rat in the lesioned group. Only 17 ~ of lesioned rats met this criterion. Each point in Figs. I and 2 is the mean of data from 3 rats save at 84 days where n -- 5. Each vertical bar indicates the standard error of the means of the controls (n = 10). Table I summarizes the representative mean values for N E and DA in the 5 brain areas 3 and 21 days after LC lesions, together with 'normal control' and bilateral 'sham' values. Unilateral brain levels of N E and D A (ng/g wet weight) on the unilateral lesioned and unilateral sham-lesioned side of the same animal were expressed as
**
* C
0.22 0.14 ~, 36 0.14 ~ 36
650 (±164) 564 (±21)
617 ( ± 47) 657 ( ± 80)
90 (±21) 80 (£12)
128 (±10) 126 (±16)
0.39 59 0.98 2
0.96
167 ( i 38) 91 ( ± 58)
98 (±18) 97 (±17)
66 ( ± 17) 89 (i 4
103 (4-8) 111 (4- 17)
C
0.47 ~ 51 0.28 ,~ 70
153 ( ± 34) 189 ( i 64)
123 (±18) 89 (~12)
72 (4- 7) 54 ( ± 17)
110 (i9) 94 (±8)
1
Posterior cerebrum
- contralateral; I -- ipsilateral. 2 bilateral sham rats were studied at 1 week. 5 bilateral sham rats were studied at 2 weeks
0.18 ~, 18 0.22 0
2.12 ,~ 31 2.77 v9
NE/DA ratios NE/DA control value 3 day % change 21 day % change 3.04
566 (4-110) 600 ( ~ 109)
834 (4-234) 377 (±97)
3.01 ~, 1 2.78 ~9
572 ( ± 44) 651 ( ± 183)
102 ( ± t0) 130 (4-20)
1760 (±68) 1043 (±3~) 556 ( ± 76) 572 (4- 26)
141 (±1) 109 (±23)
1457 (4-64) 1582 ( ± 137)
Dopamine (ng/g wet wt.) Control (n -- 10) 438 (4- 17) Bilateral sham (n - 7) 495 (4- 17) Unilateral lesioned rats 3 day (n = 3) 579 (4-137) 21 d a y ( n = 3 ) 401 (±156)
Norepinephrine (ng/g wet wt.) Control (n - 10) 1561 (4-114) Bilateral sham (n -- 7)* * 1604 (4- 102) Unilateral lesioned rats 3 day (n = 3) 1730 ( ± 128) 21 day (n -- 3) 1113 (±166)
I
C
C*
I*
Anterior cerebrum
Hypothalamus
Values in parentheses are standard error of the means.
NOREPINEPHRINE A N D DOPAMINE LEVELS IN RAT BRAIN REGIONS AFTER LEFT LOCUS COERULEUS LESION
TABLE I
0.189 ~ 58 4.39 '~ I05
2.14
111 ( ± 56) 18 ( ± 5)
64 (±12) 37 (±9)
( i 15)
99 ( ± 15) 79
121 (4-13) 141 ( ~ 18)
C
Cerebellum
0.68 ~ 68 4.70 ~ 117
94 ( i 25) 10 ( ± 2)
51 (±10) 30 (12)
64 ( ± 21) 47 ( ~ 12)
124 (±14) 169 ( ± 19)
I
1.15 ~ 61 8.21 I' 176
2.97
237 ( ± 74) 33 ( ± 17)
123 (±29) 77 (±20)
272 ( ± 67) 271 ( ± 35)
345 ( i 35) 348 (±22)
C
Medulla
1.12 ,~ 62 7.51 ~ 153
225 ( ± 77) 33 ( ± 7)
111 (~26) 111 (~23)
252 (4- 36) 248 ( ± 36)
351 (±28) 338 ( ± 31)
1
to
201 +80
Hypothalamus
*60 +40 [ \ _6 .20 / ~ . . .
oZ~ '~
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Lesion - Dopamine • Nonlesinn- Dopamine --~-Lesion- Norepinephrine --e-- Nonlesion - Norepinephrine
"x~.~,,~ * p
7
I~, 21 2'8 DaysPostLesion
/"
84
Fig. 2. Changes of NE and DA in hypothalamus after LC lesion. Asterisks represent significant difference from the control.
per cent of 'normal control' for each corresponding brain area as seen in Figs. la-d and 2. Normal control values for right and left sides of the 5 brain areas did not differ statistically and were therefore averaged to give one value for each area. Unlike findings after unilateral LC lesions, bilateral sham operations (Table I) did not cause changes in N E or DA that differed statistically from results in the unoperated 'normal control' group, but were not combined with that group. Student's t test was used for significance. Figs. l a - d and 2 show how N E and DA levels changed over the 84 day period of each brain region when related to the mean control values. NE changed remarkably. At 3 days, N E was reduced an average of 31 ~ bilaterally in all regions except the hypothalamus. In the hypothalamus at 3 days, NE increased about 10 ~ over control values, but NE levels then decreased significantly to --50 ~ of controls by the 84th day (Fig. 2). Interestingly, at 7 days, both sides of the cerebrum (anterior, posterior) and medulla tended to increase up to 27 ~ above control (Fig. la-b), whereas N E in the cerebellum and hypothalamus was generally reduced 20-40 ~ below control (Figs. la and 2). By 21 days, NE levels in all brain regions were reduced an average of 32 ~ . By 84 days, NE in medulla and cerebellum was reduced about 5 0 ~ (Fig. la), whereas most NE levels in cerebrum (anterior and posterior) had returned toward normal (Fig. lb). In contrast to the fall in NE at 3 days, DA increased an average of 47 ~ in all brain regions at the third day; chiefly in cerebellum and medulla (Fig. lc, d). DA then fell gradually in hypothalamus, cerebellum, and medulla to less than 50 ~ of control levels at 21 days, remaining low through 84 days (Figs. lc and 2). In the anterior cerebrum, DA tended to return toward normal, but in posterior cerebrum DA
202 dropped 3 0 - 6 0 ~ , then increased over 100°/~ above normal at 84 days (Fig, ld). In general, both N E and DA were reduced more in brain regions ipsilateral to the lesion. The reduction of NE is significant both in cerebellum and cerebrum, consistent with its largely uncrossed pathway. D A is converted to NE by dopamine-fl-hydroxylase. This suggests that the data might be appropriately expressed in the form of a N E / D A ratio (Table I). The baseline control ratio is interesting: hypothalamus, cerebellum and medulla have 2-3 times more N E than dopamine, but anterior cerebrum has only one-fifth as much NE, reflecting its large striatal component. The dynamics of this relationship appear to change after the lesion, and the change differs from site to site. Thus, at 21 days, the ratio in cerebrum falls to about 0.5 on the lesioned side, whereas cerebellum and medulla rise to more than 2.0. In summary, these data give a longitudinal dimension to the dynamics of the change in N E and DA after an LC lesion. Although N E is reduced 30-50 ~ on the same side as a unilateral LC lesion, N E can also increase on the contralateral side of the brain. Reis and Ross 13 noted that dopamine-fl-hydroxylase increased in activity on the contralateral side of the brain 21 days after an hypothalamic lesion. In the present study, the increased DA on the third day (Fig. lc, d) might serve partially to compensate, at least initially, for the loss of N E caused by the LC lesion 12,16. The results of this study suggest that a unilateral LC lesion can affect both catecholamines on both sides of the brain. Precise mechanisms underlying all these changes are not separately identified here but could be predicted from the bilateral crossover of ascending NE pathways 13,t4, including those connecting one LC with the other. In corroboration of the gradual fall of N E in hypothalamus, even when a discrete LC lesion does not obviously involve the subcoeruleus, some histochemical and biochemical evidence indicates that terminals in certain hypothalamic nuclei are reduced after an LC lesion 7,9A°. Based on the prior studies of K o r f et al. s, the maximum impact of an LC lesion might be expected to be on NE. That this is not necessarily the case might reflect com, pensatory mechanisms within other N E pathways, such as the subcoeruleus 1~, and/or the amount of regeneration, sprouting, and storage or release of N E within the contralateral brain ~,6,12. The present data emphasize the need to consider dynamic changes within contralateral as well as ipsilateral brain regions when using one side of one animal as a control for the other side. Supported by Grants N I H No. NS-09199-05 and N I H No. NS-09760-05.
1 BJORKLUND, A., AND STENEVI, U., Nerve growth factor: stimulation of regenerative growth of
central noradrenergic neurons, Science, I75 (1972) 1251-1253. 2 CLARK,R. G., Clinical Neuroanatomy and Neurophysiology, 5th ed., Davis, Philadelphia, Pa. 1975, pp. 130-133. 3 COYLE, J. T., AND HENRY, D. T., Catecholamines in fetal and newborn rat brain, J. Neurochem., 21 (I973) 61-67. 4 DAFILSTROM, A., AND FUXE, K., Evidence for the existence of monoamine-containing neurons in
203
5 6
7
8
9 10 11 12 13
14 15 16
the central nervous system. I. Demonstration of monoamine in the cell bodies of brain stem neurons, Acta physiol, scand., 62, Suppl. 232 (1964) 1-55. FIFKOV~,, E., AND MARSALA, J., Stereotaxie Atlases for the Cat, Rabbit, and Rat. Electrophysiological Methods in Biological Research, Academic Press, New York, 1967, pp. 653-695. KATZMAN, R., BJORKLUND, A., OWMAN, C., STENEVI, U., AND WEST, K. A., Evidence for regenerative axon sprouting of central cateeholamine neurons in the rat mesencephalon following electrolytic lesions, Brain Research, 25 (1971) 579-596. KOBAYASH1,R. M., PALKOVITS, M., JACOaOWITZ, D. M., AND KOP1N, 1. J., Biochemical mapping of the noradrenergic projection from the locus coeruleus, Neurology (Minneap.), 25 0975) 223-233. KORF, J., AGHAJANIAN, G. K., AND ROTH, R. H., Stimulation and destruction of the locus coeruleus: opposite effects on 3-methoxy-4-hydroxyphenylglycol sulfate levels in the rat cerebral cortex, Europ. J. Pharmacol., 21 (1973) 305 310. Lolzou, L. A., Projections of the nucleus locus coeruleus in the albino rat, Brain Research, 15 (1969) 563-566. MAEDA, Z., ET SHIMIZU, N., Projections ascendentes du locus coeruleus et d'autres neurones aminergiques pontiques au niveau du prosenc6phale du rat, Brain Research, 36 (1972) 19 35. OLSON, L., AND FUXE, K., Further mapping out of noradrenaline central neuron systems: projections of the subcoeruleus area, Brain Research, 43 (1972) 289-295. PORCHER, W., AND HEELER, A., Regional development of catecholamine biosynthesis in rat brain, J. Neurochem., 19 (1972) 1917-1930. RElS, D. J., AND ROSS, R. A., Dynamic changes in brain dopamine-{Lhydroxylase activity during anterograde and retrograde reactions to injury of central noradrenergic axons, Brain Research, 57 (1973) 307-326. Ross, R. A., AND RElS, D. J., Effects of lesions of locus coeruleus on regional distribution of dopamine-/J-bydroxylase activity in rat brain, Brain Research, 73 (1974) 161-166. UYGERSTEDT, U., Stereotaxic mapping of the monoamine pathways in the rat brain, Acta physiol. scand., Suppl. 367 (1971) 1 48. WORTH, W. S., A new design constant direct current lesioning device with electronic timer, J. Neurosurg., Submitted.
Brahl Research, 106 (1976) 198 203 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
Serial changes in norepinephrine and dopamine in rat brain after locus coeruleus lesions
W I L L I A M S. WORTH, J A N E T COLLINS, D O U B R A V K A KETT AND JAMES H. AUSTIN
Department of Neurology, University of Colorado Medical Center, Denver, Colo. 80220 (U.S.A.) (Accepted January 5th, 1976)
The locus coeruleus (LC) is the source of one of the major ascending norepinephrine (NE) pathways in the central nervous system 2,4. Each of the paired LC nuclei consists of a discrete collection of cell bodies in the dorsolaterat pontine tegmentum 1~. Axons from these LC neurons ascend, largely uncrossed, via the dorsal bundle to innervate the neo-, paleo-, meso-, and archicortex, and also project to the ipsilateraI cerebellum. The long-range effects that an LC lesion has on catecholamine levels still needs to be determined. Therefore, the goals of this study were: (1) to measure the effects of a unilateral LC lesion on N E and dopamine (DA) levels in pertinent areas of the brain; (2) to determine the serial changes that occur during the three months following such a lesion. The later changes should reflect the degree of compensation afforded by the contralateral LC, the dynamics of catecholamine storage, sprouting and regeneration within this lesioned neuronal pathway 8,18 and possibly other mechanisms still to be discovered. The methods are as follows. Male Sprague-Dawley rats (180-220 g) were housed 6 per cage, receiving standard food pellets and water ad lib. during a 12 h alternating light-dark cycle. Rats were anesthetized with 0.2 ml/kg s.c. of lnovar-Vet (PitmanMoore, Inc.), diluted 1/10. A discrete electrolytic lesion was placed stereotaxically in the left LC at a depth of 7.0 mm. The skull was first tilted forward 20 °, and the burr hole of entry was placed 4.0 mm occipital from the lambda and 1.2 mm lateral to the midline ~,15. The unipolar electrode was 250/tm in diameter, insulated except for 250 # m at the tip. A current of 1.5 mA was applied for 10 sec by a specifically designed direct constant current lesion maker 16. Lesions averaged 500 #m in diameter. To control for non-specific changes secondary to anesthesia or operation, the contralateral (right) side of the same rat was also 'sham' operated, but the electrode stopped in cerebellum at a depth of 5.5 mm and no current was applied. Bilateral 'sham' operations were also performed on some littermate controls (1 and 2 weeks before analysis), but again, no electrolytic lesion was made. 'Normal control' littermates received neither anesthesia nor operation. Rats were decapitated at the same time in the morning 3.7. 14. 21, 28, and 84 days post-operation. The brain was quickly removed and dissected. A thin slab from
199
•601a •401~
+100 *SO *60 *40
~o RonlesionLesi°n
,201 / / ~
/ / / / / ~ MedulLa
-4-20 -
•
o,..
~ -20
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-,
• Lesion
Ij
Nonlesion
*20
.~
-
e
~
-
~
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100
'
-.12o
" p
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,401
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Z;;
Cerebrum
/1// Posterior,.////
+60
Anterior
+40
.,
O~0
//
**
t
-iil
0 3 7
14
21
Days Post Lesion
28
84
t
0 3 7
14
21
28
84
Days Post Lesion
Fig. t. a, b, c, d: serial changes in NE and DA in rat brain regions after LC lesion. Asterisks represent significant difference from the control.
the LC region, fixed in 10 ~formalin, was stained with the Nissl technique to confirm the lesion histologically. After removing the hypothalamus, the right and left sides of the brain were next rapidly dissected into 4 discrete areas: anterior (0.5)cerebrum, posterior (0.5) cerebrum, cerebellum, and medulla. Wet weight of tissues was determined. Tissues were homogenized in 0.1 N perchloric acid (7.5 ml/g tissue) and centrifuged at 7000 × g for 10 min. Then 0.3 ml of the supernant was assayed in duplicate for N E and D A by a modification of the quantitative labeled O-methylation assay method 3. Histologic confirmation of a discrete lesion involving the LC, as illustrated by Ross and Reis t4 and Kobayashi et al. 7, was the primary basis for including a rat in the lesioned group. Only 17 ~ of lesioned rats met this criterion. Each point in Figs. I and 2 is the mean of data from 3 rats save at 84 days where n -- 5. Each vertical bar indicates the standard error of the means of the controls (n = 10). Table I summarizes the representative mean values for N E and DA in the 5 brain areas 3 and 21 days after LC lesions, together with 'normal control' and bilateral 'sham' values. Unilateral brain levels of N E and D A (ng/g wet weight) on the unilateral lesioned and unilateral sham-lesioned side of the same animal were expressed as
**
* C
0.22 0.14 ~, 36 0.14 ~ 36
650 (±164) 564 (±21)
617 ( ± 47) 657 ( ± 80)
90 (±21) 80 (£12)
128 (±10) 126 (±16)
0.39 59 0.98 2
0.96
167 ( i 38) 91 ( ± 58)
98 (±18) 97 (±17)
66 ( ± 17) 89 (i 4
103 (4-8) 111 (4- 17)
C
0.47 ~ 51 0.28 ,~ 70
153 ( ± 34) 189 ( i 64)
123 (±18) 89 (~12)
72 (4- 7) 54 ( ± 17)
110 (i9) 94 (±8)
1
Posterior cerebrum
- contralateral; I -- ipsilateral. 2 bilateral sham rats were studied at 1 week. 5 bilateral sham rats were studied at 2 weeks
0.18 ~, 18 0.22 0
2.12 ,~ 31 2.77 v9
NE/DA ratios NE/DA control value 3 day % change 21 day % change 3.04
566 (4-110) 600 ( ~ 109)
834 (4-234) 377 (±97)
3.01 ~, 1 2.78 ~9
572 ( ± 44) 651 ( ± 183)
102 ( ± t0) 130 (4-20)
1760 (±68) 1043 (±3~) 556 ( ± 76) 572 (4- 26)
141 (±1) 109 (±23)
1457 (4-64) 1582 ( ± 137)
Dopamine (ng/g wet wt.) Control (n -- 10) 438 (4- 17) Bilateral sham (n - 7) 495 (4- 17) Unilateral lesioned rats 3 day (n = 3) 579 (4-137) 21 d a y ( n = 3 ) 401 (±156)
Norepinephrine (ng/g wet wt.) Control (n - 10) 1561 (4-114) Bilateral sham (n -- 7)* * 1604 (4- 102) Unilateral lesioned rats 3 day (n = 3) 1730 ( ± 128) 21 day (n -- 3) 1113 (±166)
I
C
C*
I*
Anterior cerebrum
Hypothalamus
Values in parentheses are standard error of the means.
NOREPINEPHRINE A N D DOPAMINE LEVELS IN RAT BRAIN REGIONS AFTER LEFT LOCUS COERULEUS LESION
TABLE I
0.189 ~ 58 4.39 '~ I05
2.14
111 ( ± 56) 18 ( ± 5)
64 (±12) 37 (±9)
( i 15)
99 ( ± 15) 79
121 (4-13) 141 ( ~ 18)
C
Cerebellum
0.68 ~ 68 4.70 ~ 117
94 ( i 25) 10 ( ± 2)
51 (±10) 30 (12)
64 ( ± 21) 47 ( ~ 12)
124 (±14) 169 ( ± 19)
I
1.15 ~ 61 8.21 I' 176
2.97
237 ( ± 74) 33 ( ± 17)
123 (±29) 77 (±20)
272 ( ± 67) 271 ( ± 35)
345 ( i 35) 348 (±22)
C
Medulla
1.12 ,~ 62 7.51 ~ 153
225 ( ± 77) 33 ( ± 7)
111 (~26) 111 (~23)
252 (4- 36) 248 ( ± 36)
351 (±28) 338 ( ± 31)
1
to
201 +80
Hypothalamus
*60 +40 [ \ _6 .20 / ~ . . .
oZ~ '~
-
I s
-80
-I°°0 3
"~-,,_
\
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T T
~-"~ ~x
-20
Lesion - Dopamine • Nonlesinn- Dopamine --~-Lesion- Norepinephrine --e-- Nonlesion - Norepinephrine
"x~.~,,~ * p
7
I~, 21 2'8 DaysPostLesion
/"
84
Fig. 2. Changes of NE and DA in hypothalamus after LC lesion. Asterisks represent significant difference from the control.
per cent of 'normal control' for each corresponding brain area as seen in Figs. la-d and 2. Normal control values for right and left sides of the 5 brain areas did not differ statistically and were therefore averaged to give one value for each area. Unlike findings after unilateral LC lesions, bilateral sham operations (Table I) did not cause changes in N E or DA that differed statistically from results in the unoperated 'normal control' group, but were not combined with that group. Student's t test was used for significance. Figs. l a - d and 2 show how N E and DA levels changed over the 84 day period of each brain region when related to the mean control values. NE changed remarkably. At 3 days, N E was reduced an average of 31 ~ bilaterally in all regions except the hypothalamus. In the hypothalamus at 3 days, NE increased about 10 ~ over control values, but NE levels then decreased significantly to --50 ~ of controls by the 84th day (Fig. 2). Interestingly, at 7 days, both sides of the cerebrum (anterior, posterior) and medulla tended to increase up to 27 ~ above control (Fig. la-b), whereas N E in the cerebellum and hypothalamus was generally reduced 20-40 ~ below control (Figs. la and 2). By 21 days, NE levels in all brain regions were reduced an average of 32 ~ . By 84 days, NE in medulla and cerebellum was reduced about 5 0 ~ (Fig. la), whereas most NE levels in cerebrum (anterior and posterior) had returned toward normal (Fig. lb). In contrast to the fall in NE at 3 days, DA increased an average of 47 ~ in all brain regions at the third day; chiefly in cerebellum and medulla (Fig. lc, d). DA then fell gradually in hypothalamus, cerebellum, and medulla to less than 50 ~ of control levels at 21 days, remaining low through 84 days (Figs. lc and 2). In the anterior cerebrum, DA tended to return toward normal, but in posterior cerebrum DA
202 dropped 3 0 - 6 0 ~ , then increased over 100°/~ above normal at 84 days (Fig, ld). In general, both N E and DA were reduced more in brain regions ipsilateral to the lesion. The reduction of NE is significant both in cerebellum and cerebrum, consistent with its largely uncrossed pathway. D A is converted to NE by dopamine-fl-hydroxylase. This suggests that the data might be appropriately expressed in the form of a N E / D A ratio (Table I). The baseline control ratio is interesting: hypothalamus, cerebellum and medulla have 2-3 times more N E than dopamine, but anterior cerebrum has only one-fifth as much NE, reflecting its large striatal component. The dynamics of this relationship appear to change after the lesion, and the change differs from site to site. Thus, at 21 days, the ratio in cerebrum falls to about 0.5 on the lesioned side, whereas cerebellum and medulla rise to more than 2.0. In summary, these data give a longitudinal dimension to the dynamics of the change in N E and DA after an LC lesion. Although N E is reduced 30-50 ~ on the same side as a unilateral LC lesion, N E can also increase on the contralateral side of the brain. Reis and Ross 13 noted that dopamine-fl-hydroxylase increased in activity on the contralateral side of the brain 21 days after an hypothalamic lesion. In the present study, the increased DA on the third day (Fig. lc, d) might serve partially to compensate, at least initially, for the loss of N E caused by the LC lesion 12,16. The results of this study suggest that a unilateral LC lesion can affect both catecholamines on both sides of the brain. Precise mechanisms underlying all these changes are not separately identified here but could be predicted from the bilateral crossover of ascending NE pathways 13,t4, including those connecting one LC with the other. In corroboration of the gradual fall of N E in hypothalamus, even when a discrete LC lesion does not obviously involve the subcoeruleus, some histochemical and biochemical evidence indicates that terminals in certain hypothalamic nuclei are reduced after an LC lesion 7,9A°. Based on the prior studies of K o r f et al. s, the maximum impact of an LC lesion might be expected to be on NE. That this is not necessarily the case might reflect com, pensatory mechanisms within other N E pathways, such as the subcoeruleus 1~, and/or the amount of regeneration, sprouting, and storage or release of N E within the contralateral brain ~,6,12. The present data emphasize the need to consider dynamic changes within contralateral as well as ipsilateral brain regions when using one side of one animal as a control for the other side. Supported by Grants N I H No. NS-09199-05 and N I H No. NS-09760-05.
1 BJORKLUND, A., AND STENEVI, U., Nerve growth factor: stimulation of regenerative growth of
central noradrenergic neurons, Science, I75 (1972) 1251-1253. 2 CLARK,R. G., Clinical Neuroanatomy and Neurophysiology, 5th ed., Davis, Philadelphia, Pa. 1975, pp. 130-133. 3 COYLE, J. T., AND HENRY, D. T., Catecholamines in fetal and newborn rat brain, J. Neurochem., 21 (I973) 61-67. 4 DAFILSTROM, A., AND FUXE, K., Evidence for the existence of monoamine-containing neurons in
203
5 6
7
8
9 10 11 12 13
14 15 16
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