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Regional distribution of dopamine D1 and D2 receptors in the nucleus accumbens of the rat
Brain Research, 501 (1989) 389-391 Elsevier
389
BRES 23775
Regional distribution of dopamine D 1 and D= receptors in the nucleus accurnbens of the rat Rosemary Allin, Vivienne Russell, Mania Lamm and Joshua Taljaard MRC Research Unit for the Neurochemistry of Mental Diseases, Department of Chemical Pathology, University of Stellenbosch, Tygerberg Hospital, Tygerberg (South Africa)
(Accepted 11 July 1989) Key words: Dopamine; Receptor, D1-; Receptor, D2-; Nucleus accumbens; Dopamine uptake
Doparnine (DA) D~ receptor density was found to be significantly lower in the rostral than in the medial and caudal areas of the nucleus accumbens. This roughly followed the distribution of DA terminals. The distribution of DAD 2 receptors did not follow the DA terminal distribution. DAD 2 receptor number was lower in the ventrorostral and higher in the dorsomedial area than in
any other area of the nucleus accumbens. Depression has been suggested to be associated with hypoactivity of a reward system in which the mesolimbic dopaminergic neurons are involved 1L13. The nucleus accumbens is a major terminal area for t h e s e neurons which originate in the ventral tegmental area of the midbrain 8"9. There has been histological evidence that the nucleus accumbens is not a homogeneously organized structure 3"4 and we have previously reported regional differences in monoamine content 1. D A receptors have been classified into two major subtypes: D A D~ and D 2 receptors 7. Both of these receptor subtypes have been demonstrated to be present in the nucleus accumbens 2"5"~2. The aim of this study was to investigate the distribution of D A D 1 and D 2 receptors within the nucleus accumbens, and to determine whether their distribution correlated with D A content or uptake. [3H]DA and [14C]choline uptake were used as an indication of the number of D A and acetylcholine (ACh) terminals within different regions of the nucleus accumbens. Male Wistar rats (250-280 g) were sacrificed by decapitation, the brains rapidly removed and the nucleus accumbens dissected into 6 areas as described previously ~. The dorsomedial area of the nucleus accumbens was further subdivided into
medial and lateral regions for D A D 2 receptor binding assays. Tissue pooled from 4-15 rats was thawed and D A D 1 and D 2 receptor assays w e r e performed, as described previously 1°, using [3H]SCH23390 80 Ci/mmol (Amersham International; 0.02-3.0 nM) and [3H]spiperone 85 Ci/mmol (Amersham International; 0.04-2.0 nM) with 1/~M c/s-flupenthixol (Lundbeck) and 10 /~M sulpiride (Sigma), respectively, to define non-specific binding. Ketanserin (Janssen; 3 or 30 nM) was included throughout to mask binding to serotonin $2 sites. Uptake studies were performed on freshly prepared tissue slices as described previously I except that dorsal and ventral areas of the rostral and medial parts of the nucleus accumbens were used. Specific 3,4-[7-3H]dopamine (38 Ci/mmol; 0.1 /~M) and [methyl-lac]choline chloride (52 mCi/mmol; 4/~M) (both from New England Nuclear) uptake was defined as the difference between the radioactivity taken up by the slices at 37 °C and 0 °C. Bma x and K d values for dopamine D 1 and D2 receptors in the 6 areas of the nucleus accumbens are shown in Table I and provide evidence for the heterogeneity of distribution of both D A D1 and D 2 receptors within the nucleus accumbens of the rat. The D A Dt receptor density was 3-9 times higher
Correspondence: R. Allin, Department of Chemical Pathology, Tygerberg Hospital, P.O. Box 113, Tygerberg 7505, South Africa.
0006-8993/89/$03.50 © 1989 Elsevier Science Publishers B.V. (Biomedical Division)
390 TABLE I Distribution of DA D 1and D 2 receptor density (Bin,=) and affinity (K a) in the nucleus accumbens of the rat
Results are the mean + S.E.M. of 5-6 observations. Nucleus accumbens area
[3H] S CH23390 binding
[3H] Spiperone binding
Bmax (fmol/mg protein)
K a (nM)
Bmax (fmol/mg protein)
K d (nM)
Dorsorostral Ventrorostral
124.7 + 18.9a 137.1 + 21.0a
0.125 + 0.028b 0.294 + 0.041
101.1 + 7.1 15.3 + 1.1c
0.054 + 0.013 0.024 + 0.013c
Dorsomedial Ventromedial
593.8 + 45.4 498.6 + 40.8
0.377 + 0.026 0.360 + 0.026
195.8 + 10.4d 104.1 + 5.7
0.054 + 0.005 0.041 + 0.003
Dorsocaudal Ventrocaudal
706.8 + 82.2 681.6 + 104.8
0.364 + 0.052 0.419 + 0.067
102.8 + 6.2 116.3 + 4.4
0.049 + 0.007 0.053 + 0.009
Significant difference: avs dorsomedial, ventromedial, dorsocaudal and ventrocaudal areas; bVS ventrorostral, dorsomedial, ventromedial, dorsocaudal, and ventrocaudal areas; Cvs dorsorostral, dorsomediai, ventromedial, dorsocaudal, and ventrocaudal areas; %s dorsorostral, ventrorostral, ventromedial, dorsocaudal, and ventrocaudal areas (P < 0.05, Tukey's studentized range test).
than the D A D 2 receptor density in the nucleus accumbens. This is consistent with a previous
pmol/mg protein/15 min, respectively) and D A content I were 2-2.5 times lower ventrally than
report 6. The dopamine D 1 receptor n u m b e r was significantly lower in the rostral area than in the medial and caudal areas (Table I; Fig. 1). There
dorsally whereas D A D1 receptors were evenly distributed dorsoventrally. D A turnover has previ-
were no dorsoventral differences. This roughly followed the D A innervation as measured by content and [3H]DA uptake 1. In the rostral accumbens D A uptake which was significantly lower in the ventrorostral (2.79 + 0.17 pmol/mg protein/15 min) than in the dorsorostral, dorsomedial and ventromedial areas (5.59 + 0.75, 7.88 + 0.80 and 8.10 + 0.56
Brnax (Imol/mg'
protein)
CAUDAL =~ I
MEDIAL
•600
DORSAL•400 ---0
•
200
ROSTRAL ~
.
.
1
.
t
.
,200
VENTRAL' 400 '600
I~IDA
DIReceptor|
BDA
D2 Receptors
+ I
t l
Fig. 1. Distribution of DA D 1 and D2 receptors (Bmax) in the nucleus accumbens. Results are the mean + S.E.M. of 5-6 observations.
ously been shown to be significantly higher in the ventrorostral area of the nucleus accumbens than in the dorsorostral area 1, suggesting that although there are fewer D A terminals in the ventrorostral area, these n e u r o n s are more active than in the dorsorostral area and can therefore activate a similar n u m b e r of postsynaptic D A D 1 receptors. The K d value for D A D1 receptors in the dorsorostral area and for D A D 2 receptors in the ventrorostral area of the nucleus accumbens was significantly lower than in any other area. This could be due to reduced accuracy in m e a s u r e m e n t of K d when the receptor n u m b e r is low. The dopamine D 2 receptor n u m b e r was significantly lower in the ventrorostral area, significantly higher in the dorsomedial area and similar in the remaining areas of the nucleus accumbens (Table I, Fig. 1). There were no significant differences in Bmax (179.7 + 4.6 and 177.5 + 10.2 fmol/mg protein) or K d (0.039 + 0.007 and 0.038 + 0.007 nM) between medial and lateral regions of the dorsomedial area of the nucleus accumbens thus localizing the highest density of D A D 2 receptors to this area. Although twice as m a n y D A D 2 receptors were present in the dorsomedial nucleus accumbens as in the ventrome-
391 dial area, D A and cholinergic innervation of these areas a p p e a r e d to be quite similar. Like [3H]DA, [14C]choline u p t a k e was significantly lower in the ventrorostral (204 + 11 pmol/mg protein/15 rain) than in the dorsorostral (277 + 27 pmol/mg protein/ 15 rain) a r e a of the nucleus accumbens but similar in the dorso- and v e n t r o m e d i a l areas (360 + 23 and 376 + 16 p m o l / m g protein/15 min, respectively). O n e e x p l a n a t i o n for the difference could be that there are m o r e D A D 2 a u t o r e c e p t o r s on the dopaminergic terminals in the d o r s o m e d i a l area; however, this does not seem likely since D A turnover was not lower in the d o r s o m e d i a l a r e a 1. A n o t h e r could be
that there are m o r e D A D 2 receptors situated postsynaptically, for e x a m p l e , on cholinergic terminals. E v i d e n c e supporting this possibility has recently b e e n o b t a i n e d (Russell et al., unpublished).
1 Allin, R., Russell, V.A., Lamm, M.C.L. and Taljaard, J.J.F., Regional distribution of monoamines in the nucleus accumbens of the rat, Neurochem. Res., 13 (1988) 937-942. 2 Camus, A., Javoy-Agid, F., Dubois, A. and Scatton, B., Autoradiographic localization and quantification of dopamine D 2 receptors in normal human brain with [3n]Nn-propylnorapomorphine, Brain Research, 375 (1986) 135149. 3 De France, J.F., Sikes, R.W. and Gottesfeld, Z., Regional distribution of catecholamines in nucleus accumbens of the rabbit, J. Neurochem., 40 (1983) 291-293. 4 Herkenham, M., Edley, S.M. and Stuart, J., Cell clusters in" the nucleus accumbens of the rat, and the mosaic relationship of receptors, acetylchohnesterase and subcortical afferent terminations, Neuroscience, 11 (1984) 561593. 5 Hyttel, J. and Arnt, J., Characterization of binding of 3H-SCH 23390 to dopamine D-1 receptors. Correlation to other D-1 and D-2 measures and effect of selective lesions, J. Neural Transm., 68 (1987) 171-189. 6 Hyttel, J. and Arnt, J., Characterization of dopamine D1 and D2 receptors, Adv. Exp. Med. Biol., 204 (1986) 15-28.
7 Kebabian, J.W. and Calne, D.B., Multiple receptors for dopamine, Nature (Lond.), 277 (1979) 93-96. 8 Lindvall, O. an~l Bj6rklund, A., The organization of the ascending catecholamine neuron systems in the rat brain, Acta Physiol. Scand., Suppl., 412 (1974) 1-48. 9 Oades, R.D. and Halliday, G.M., Ventral tegmental (A10) system: neurobiology. 1. Anatomy and connectivity, Brain Research, 6 (1987) 225-236. 10 Reyneke, L., Allin, R., Russell, V.A. and Taljaard, J.J.E, Lack of effect of chronic desipramine treatment on dopaminergic activity in the nucleus accumbens of the rat, Neurochem. Res., in press. 11 Spyraki, C., Fibiger, H.C. and Phillips, A.G., Dopaminergic substrates of amphetamine-induced place preference conditioning, Brain Research, 253 (1982) 185-193. 12 White, F.J. and Wang, R.Y., Electrophysiologicalevidence for the existence of both D-1 and D-2 dopamine receptors in the rat nucleus accumbens, J. Neurosci., 6 (1986) 274-280. 13 Willner, P., Dopamine and depression: a review of recent evidence. II. Theoretical approaches, Brain Research, 6 (1983) 225-236.
This research was s u p p o r t e d by the South African Medical R e s e a r c h Council and the C a p e Provincial A d m i n i s t r a t i o n . T h e authors wish to t h a n k Dr. R. Schall of the M R C Institute for Biostatistics for statistical analysis of the data. This w o r k forms p a r t of the P h . D . thesis of R . A . , c o m p l e t e d at the University of Stellenbosch.
389
BRES 23775
Regional distribution of dopamine D 1 and D= receptors in the nucleus accurnbens of the rat Rosemary Allin, Vivienne Russell, Mania Lamm and Joshua Taljaard MRC Research Unit for the Neurochemistry of Mental Diseases, Department of Chemical Pathology, University of Stellenbosch, Tygerberg Hospital, Tygerberg (South Africa)
(Accepted 11 July 1989) Key words: Dopamine; Receptor, D1-; Receptor, D2-; Nucleus accumbens; Dopamine uptake
Doparnine (DA) D~ receptor density was found to be significantly lower in the rostral than in the medial and caudal areas of the nucleus accumbens. This roughly followed the distribution of DA terminals. The distribution of DAD 2 receptors did not follow the DA terminal distribution. DAD 2 receptor number was lower in the ventrorostral and higher in the dorsomedial area than in
any other area of the nucleus accumbens. Depression has been suggested to be associated with hypoactivity of a reward system in which the mesolimbic dopaminergic neurons are involved 1L13. The nucleus accumbens is a major terminal area for t h e s e neurons which originate in the ventral tegmental area of the midbrain 8"9. There has been histological evidence that the nucleus accumbens is not a homogeneously organized structure 3"4 and we have previously reported regional differences in monoamine content 1. D A receptors have been classified into two major subtypes: D A D~ and D 2 receptors 7. Both of these receptor subtypes have been demonstrated to be present in the nucleus accumbens 2"5"~2. The aim of this study was to investigate the distribution of D A D 1 and D 2 receptors within the nucleus accumbens, and to determine whether their distribution correlated with D A content or uptake. [3H]DA and [14C]choline uptake were used as an indication of the number of D A and acetylcholine (ACh) terminals within different regions of the nucleus accumbens. Male Wistar rats (250-280 g) were sacrificed by decapitation, the brains rapidly removed and the nucleus accumbens dissected into 6 areas as described previously ~. The dorsomedial area of the nucleus accumbens was further subdivided into
medial and lateral regions for D A D 2 receptor binding assays. Tissue pooled from 4-15 rats was thawed and D A D 1 and D 2 receptor assays w e r e performed, as described previously 1°, using [3H]SCH23390 80 Ci/mmol (Amersham International; 0.02-3.0 nM) and [3H]spiperone 85 Ci/mmol (Amersham International; 0.04-2.0 nM) with 1/~M c/s-flupenthixol (Lundbeck) and 10 /~M sulpiride (Sigma), respectively, to define non-specific binding. Ketanserin (Janssen; 3 or 30 nM) was included throughout to mask binding to serotonin $2 sites. Uptake studies were performed on freshly prepared tissue slices as described previously I except that dorsal and ventral areas of the rostral and medial parts of the nucleus accumbens were used. Specific 3,4-[7-3H]dopamine (38 Ci/mmol; 0.1 /~M) and [methyl-lac]choline chloride (52 mCi/mmol; 4/~M) (both from New England Nuclear) uptake was defined as the difference between the radioactivity taken up by the slices at 37 °C and 0 °C. Bma x and K d values for dopamine D 1 and D2 receptors in the 6 areas of the nucleus accumbens are shown in Table I and provide evidence for the heterogeneity of distribution of both D A D1 and D 2 receptors within the nucleus accumbens of the rat. The D A Dt receptor density was 3-9 times higher
Correspondence: R. Allin, Department of Chemical Pathology, Tygerberg Hospital, P.O. Box 113, Tygerberg 7505, South Africa.
0006-8993/89/$03.50 © 1989 Elsevier Science Publishers B.V. (Biomedical Division)
390 TABLE I Distribution of DA D 1and D 2 receptor density (Bin,=) and affinity (K a) in the nucleus accumbens of the rat
Results are the mean + S.E.M. of 5-6 observations. Nucleus accumbens area
[3H] S CH23390 binding
[3H] Spiperone binding
Bmax (fmol/mg protein)
K a (nM)
Bmax (fmol/mg protein)
K d (nM)
Dorsorostral Ventrorostral
124.7 + 18.9a 137.1 + 21.0a
0.125 + 0.028b 0.294 + 0.041
101.1 + 7.1 15.3 + 1.1c
0.054 + 0.013 0.024 + 0.013c
Dorsomedial Ventromedial
593.8 + 45.4 498.6 + 40.8
0.377 + 0.026 0.360 + 0.026
195.8 + 10.4d 104.1 + 5.7
0.054 + 0.005 0.041 + 0.003
Dorsocaudal Ventrocaudal
706.8 + 82.2 681.6 + 104.8
0.364 + 0.052 0.419 + 0.067
102.8 + 6.2 116.3 + 4.4
0.049 + 0.007 0.053 + 0.009
Significant difference: avs dorsomedial, ventromedial, dorsocaudal and ventrocaudal areas; bVS ventrorostral, dorsomedial, ventromedial, dorsocaudal, and ventrocaudal areas; Cvs dorsorostral, dorsomediai, ventromedial, dorsocaudal, and ventrocaudal areas; %s dorsorostral, ventrorostral, ventromedial, dorsocaudal, and ventrocaudal areas (P < 0.05, Tukey's studentized range test).
than the D A D 2 receptor density in the nucleus accumbens. This is consistent with a previous
pmol/mg protein/15 min, respectively) and D A content I were 2-2.5 times lower ventrally than
report 6. The dopamine D 1 receptor n u m b e r was significantly lower in the rostral area than in the medial and caudal areas (Table I; Fig. 1). There
dorsally whereas D A D1 receptors were evenly distributed dorsoventrally. D A turnover has previ-
were no dorsoventral differences. This roughly followed the D A innervation as measured by content and [3H]DA uptake 1. In the rostral accumbens D A uptake which was significantly lower in the ventrorostral (2.79 + 0.17 pmol/mg protein/15 min) than in the dorsorostral, dorsomedial and ventromedial areas (5.59 + 0.75, 7.88 + 0.80 and 8.10 + 0.56
Brnax (Imol/mg'
protein)
CAUDAL =~ I
MEDIAL
•600
DORSAL•400 ---0
•
200
ROSTRAL ~
.
.
1
.
t
.
,200
VENTRAL' 400 '600
I~IDA
DIReceptor|
BDA
D2 Receptors
+ I
t l
Fig. 1. Distribution of DA D 1 and D2 receptors (Bmax) in the nucleus accumbens. Results are the mean + S.E.M. of 5-6 observations.
ously been shown to be significantly higher in the ventrorostral area of the nucleus accumbens than in the dorsorostral area 1, suggesting that although there are fewer D A terminals in the ventrorostral area, these n e u r o n s are more active than in the dorsorostral area and can therefore activate a similar n u m b e r of postsynaptic D A D 1 receptors. The K d value for D A D1 receptors in the dorsorostral area and for D A D 2 receptors in the ventrorostral area of the nucleus accumbens was significantly lower than in any other area. This could be due to reduced accuracy in m e a s u r e m e n t of K d when the receptor n u m b e r is low. The dopamine D 2 receptor n u m b e r was significantly lower in the ventrorostral area, significantly higher in the dorsomedial area and similar in the remaining areas of the nucleus accumbens (Table I, Fig. 1). There were no significant differences in Bmax (179.7 + 4.6 and 177.5 + 10.2 fmol/mg protein) or K d (0.039 + 0.007 and 0.038 + 0.007 nM) between medial and lateral regions of the dorsomedial area of the nucleus accumbens thus localizing the highest density of D A D 2 receptors to this area. Although twice as m a n y D A D 2 receptors were present in the dorsomedial nucleus accumbens as in the ventrome-
391 dial area, D A and cholinergic innervation of these areas a p p e a r e d to be quite similar. Like [3H]DA, [14C]choline u p t a k e was significantly lower in the ventrorostral (204 + 11 pmol/mg protein/15 rain) than in the dorsorostral (277 + 27 pmol/mg protein/ 15 rain) a r e a of the nucleus accumbens but similar in the dorso- and v e n t r o m e d i a l areas (360 + 23 and 376 + 16 p m o l / m g protein/15 min, respectively). O n e e x p l a n a t i o n for the difference could be that there are m o r e D A D 2 a u t o r e c e p t o r s on the dopaminergic terminals in the d o r s o m e d i a l area; however, this does not seem likely since D A turnover was not lower in the d o r s o m e d i a l a r e a 1. A n o t h e r could be
that there are m o r e D A D 2 receptors situated postsynaptically, for e x a m p l e , on cholinergic terminals. E v i d e n c e supporting this possibility has recently b e e n o b t a i n e d (Russell et al., unpublished).
1 Allin, R., Russell, V.A., Lamm, M.C.L. and Taljaard, J.J.F., Regional distribution of monoamines in the nucleus accumbens of the rat, Neurochem. Res., 13 (1988) 937-942. 2 Camus, A., Javoy-Agid, F., Dubois, A. and Scatton, B., Autoradiographic localization and quantification of dopamine D 2 receptors in normal human brain with [3n]Nn-propylnorapomorphine, Brain Research, 375 (1986) 135149. 3 De France, J.F., Sikes, R.W. and Gottesfeld, Z., Regional distribution of catecholamines in nucleus accumbens of the rabbit, J. Neurochem., 40 (1983) 291-293. 4 Herkenham, M., Edley, S.M. and Stuart, J., Cell clusters in" the nucleus accumbens of the rat, and the mosaic relationship of receptors, acetylchohnesterase and subcortical afferent terminations, Neuroscience, 11 (1984) 561593. 5 Hyttel, J. and Arnt, J., Characterization of binding of 3H-SCH 23390 to dopamine D-1 receptors. Correlation to other D-1 and D-2 measures and effect of selective lesions, J. Neural Transm., 68 (1987) 171-189. 6 Hyttel, J. and Arnt, J., Characterization of dopamine D1 and D2 receptors, Adv. Exp. Med. Biol., 204 (1986) 15-28.
7 Kebabian, J.W. and Calne, D.B., Multiple receptors for dopamine, Nature (Lond.), 277 (1979) 93-96. 8 Lindvall, O. an~l Bj6rklund, A., The organization of the ascending catecholamine neuron systems in the rat brain, Acta Physiol. Scand., Suppl., 412 (1974) 1-48. 9 Oades, R.D. and Halliday, G.M., Ventral tegmental (A10) system: neurobiology. 1. Anatomy and connectivity, Brain Research, 6 (1987) 225-236. 10 Reyneke, L., Allin, R., Russell, V.A. and Taljaard, J.J.E, Lack of effect of chronic desipramine treatment on dopaminergic activity in the nucleus accumbens of the rat, Neurochem. Res., in press. 11 Spyraki, C., Fibiger, H.C. and Phillips, A.G., Dopaminergic substrates of amphetamine-induced place preference conditioning, Brain Research, 253 (1982) 185-193. 12 White, F.J. and Wang, R.Y., Electrophysiologicalevidence for the existence of both D-1 and D-2 dopamine receptors in the rat nucleus accumbens, J. Neurosci., 6 (1986) 274-280. 13 Willner, P., Dopamine and depression: a review of recent evidence. II. Theoretical approaches, Brain Research, 6 (1983) 225-236.
This research was s u p p o r t e d by the South African Medical R e s e a r c h Council and the C a p e Provincial A d m i n i s t r a t i o n . T h e authors wish to t h a n k Dr. R. Schall of the M R C Institute for Biostatistics for statistical analysis of the data. This w o r k forms p a r t of the P h . D . thesis of R . A . , c o m p l e t e d at the University of Stellenbosch.