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Home , Caudate nucleus, Globus pallidus, Islands of Calleja, Putamen

Proc. NatI. Acad. Sci. USA Vol. 91, pp. 11271-11275, November 1994 Pharmacology Localization of D3 receptors to mesolimbic and D2 receptors to mesostriatal regions of human ( accumbens///ventral tegnental area/pallidum) ANGELA M. MURRAY*, HAN L. Ryoot, EUGENIA GuREVICH, AND JEFFREY N. JOYCEO Departments of Psychiatry and Pharmacology, University of Pennsylvania, Philadelphia, PA 19104-6141 Communicated by William T. Greenough, July 19, 1994

ABSTRACT We characterized the binding of [125I~epide- transfected Chinese hamster ovary (CHO) cells (9, 10). In the pride to dopamine D2-like and D3-like receptors in tissue presence of GTP, binding of agonists to the D2 receptor sections of human . The competition for binding of shows a rightward displacement in the competition curve. [125I]epidepride by domperidone, quinpirole, and 7-hydroxy- The data indicate there is a complete conversion to the N,N-di(l-propyl)-2-aminotetralin (7-OH-DPAT) was best fit low-affinity site ofthe D2 receptor. In contrast, binding to the by assuming one site in the caudate but two sites in nucleus human D3 receptor shows a minor GTP-induced shift (9, 10). accumbens. Guanosine 5'-[3,v-imidoltriphosphate showed a These properties allow for increased selectivity for the dis- large modulatory influence in agonist inhibition of [12(I]epide- placement ofnonselective radioligands by the agonists 7-OH- pride binding in caudate but not in . The DPAT and quinpirole. In this paper we have used the binding of [125I~epidepride in the presence of 7-OH-DPAT selective displacement of [1251]epidepride from D3 receptors (1000-fold selective for D3-like versus D2-like sites) and dom- with 7-OH-DPAT and partial displacement from D2 receptors peridone (20-fold selective for D2-like versus D3-like sites) was with domperidone to quantify the distribution of [1251]epide- used to quantify the numbers of D2-like and D3-like receptors pride-bound D2-like and D3-like receptors in the in areas ofhuman . The distribution ofD2-like and D3-like and limbic regions of . receptors was largely nonoverlapping. Binding of [125I~epide- pride to D3-like receptors was negligible in the dorsal striatum but was concentrated in islands of dense binding in the nucleus MATERIALS AND METHODS accumbens and ventral that aligned with acetylcho- inetic Experiments. Tissue was obtained post mortem linesterase-poor striosomes. Binding to D3-like receptors was from 24 normal individuals (mean age ± SD, 68 + 14 yr; also enriched in the internal , ventral pallidum, postmortem interval of 9.2 + 6 hr; 17 males, 7 females). For septum, , nucleus basalis, amygdalostriatal all kinetic experiments 20-gm-thick slide-mounted human transition nucleus of the amygdala, central nucleus of the tissue sections of striatum (containing caudate, putamen, and amygdala, and . Binding of [12I5epide- nucleus accumbens) or inferior were preincu- pride to D2 but not D3 receptors was detected in cortex and bated for 30 min in ice-cold TBS (50 mM Tris-HCl/120 mM . NaCl, pH 7.4) and then for 25 min in TBS at room temper- ature. The preincubation step was utilized to remove the There are two superfamilies of dopamine receptors, desig- high-affinity binding of dopamine to the D3 receptor (2). To nated Dj-like and D2-like (1). This nomenclature is based on establish optimal conditions for the binding of [125I]epide- their structural and amino acid similarities, as well as their pride, sections of striatum were incubated in TBS and the binding profiles. The D2-like family contains D2, D3, and D4 a2-adrenergic antagonist idazoxan (100 nM) containing 50 pM subtypes, which differ with respect to their distribution in rat [1251]epidepride at 22°C, 30°C, or 37°C for various intervals brain (2-4). Much interest has been focused on the D3 (30-300 min). Results are the means of triplicate determina- receptor because of its high association with "limbic" com- tions for four . Following establishment of optimal ponents of the rat brain (e.g., ventral striatum) and high conditions for binding, competition experiments with 18 affinity for dopamine (2, 5). In fact, it has been proposed that differing concentrations of domperidone (0.01-1000 nM), the D3 receptor is the "limbic" through 7-OH-DPAT (0.1-10,000 nM), and quinpirole (1-100,000 nM) which could act to modify psychosis (5). and one concentration of raclopride (300 nM) for ['25I]epide- However, extension of this hypothesis to the human is pride binding were carried out in the presence and absence of limited by the lack of a detailed mapping of the distribution guanosine 5'-[(3,y-imido]triphosphate (p[NH]ppG; 100 ,M). of the D3 receptor in this species. Such mapping can be Results are the means of triplicate determinations for four accomplished by selectively displacing radioligands nonse- brains, expressed as the percentage of total specific binding lective for D2 and D3 receptors from each receptor site (6). In measured in the absence of any displacing drug. Saturation preliminary studies we utilized that approach to detect the isotherms were established by conducting saturation binding presence of D2-like and D3-like receptors in striatal tissue of [1251]epidepride to striatum and inferior temporal cortex sections with [1251]epidepride (7). The potency of substituted benzamide derivatives similar to [125I]epidepride is only Abbreviations: 7-OH-DPAT, 7-hydroxy-N,N-di(l-propyl)-2-amino- at the tetralin; p(NH]ppG, guanosine 5'-[3,.-iimido]triphosphate; AChE, marginally lower D3 receptor than at the D2 receptor acetylcholinesterase; GPi, globus pallidus internal; GPe, globus (8). Further, drugs such as domperidone, quinpirole, and pallidus external. 7-hydroxy-N,N-di(1-propyl)-2-aminotetralin (7-OH-DPAT) *Present address: Division of Intramural Research Programs, Na- show 32- to 100-fold selectivity for the human D2 or D3 tional Institute of Mental Health Neuropsychiatric Research Hos- receptor labeled with [1251]iodosulpride in membranes of pital, Washington, DC 20032. tPresent address: Department of Neurobiology and Anatomy, Uni- versity of Rochester, Rochester, NY. The publication costs of this article were defrayed in part by page charge tTo whom reprint requests should be addressed at: Department of payment. This article must therefore be hereby marked "advertisement" Psychiatry, 127 Clinical Research Building, 415 Currie Boulevard, in accordance with 18 U.S.C. §1734 solely to indicate this fact. Philadelphia, PA 19104-6141. 11271 Downloaded by guest on September 30, 2021 11272 Pharmacology: Murray et al. Proc. Natl. Acad Sci. USA 91 (1994) with increasing concentrations of ['251]epidepride (3-500 pM) Caudate in triplicate from four individuals. In all experiments, sec- tions were rinsed, dried, and laid against film for 18 hr (striatum) or 7 days (inferior temporal cortex). Nonspecific binding was determined in the presence of 5 ILM (+)- butaclamol. Competition curves were analyzed by comput- erized nonlinear regression, using either a one-site or a two-site cooperative model to estimate IC50 values and the proportion of sites (11). Saturation curves were analyzed by computer nonlinear regression, using a one-site and two-site cooperative model to obtain equilibrium dissociation con- stants (Kd) and maximal density of receptors (Bmax). Mapping Experiment. The 20-Ium-thick slide-mounted hu- 100000 man tissue sections were preincubated as before and then incubated in TBS and idazoxan (100 nM) at 300C containing 50 pM [125I]epidepride and p[NH]ppG (100 ttM) for 100 min. Adjacent sections were incubated similarly but contained 50 nM 7-OH-DPAT to displace [1251]epidepride binding to D3 co receptors, allowing detection of D2 receptors, or 10 nM '0 domperidone to partially exclude D2 receptors to visualize D3 receptors. Nonspecific binding was determined in the pres- ence of 5 juM (+)-butaclamol. Sections were rinsed, dried, ut and laid against film for the appropriate time. Sections adjacent to those used for autoradiographic experiments were processed for acetylcholinesterase (AChE) histochem- istry or cresyl violet histochemistry for aid in the identifica- tion of regions of interest (12). The maximal density of sites was estimated from the single-concentration mapping exper- iments by using the equation Bma = [B]([L] + Kd)/[L], where [B] represents the amount bound at the concentration of FIG. 1. Inhibition of (1251]epidepride binding by quinpirole, dom- ligand [L] (11). Results are the means of triplicate determi- peridone, or 7-OH-DPAT in tissue sections containing caudate (A) or nations for a minimum offour brains for any region. For these nucleus accumbens (B). Means of four independent experiments are studies, four sections for total binding and two sections for shown. Computer-drawn curves of quinpirole (o, *) inhibition of [1251]epidepride binding in the presence of p[NH]ppG show a large nonspecific binding for each level were analyzed for each rightward shift for caudate and much smaller shift for the nucleus case. An average value for specific binding was obtained for accumbens. It was best fit by assuming one class of sites in the each individual for any region of interest. For the mapping of caudate and two classes of sites in the nucleus accumbens. Displace- D2 and D3 receptor sites the differences between regions were ment of [125I]epidepride binding by domperidone (o, *) was also best tested for significance by analysis ofcovariance (ANCOVA). fit by assuming one class of sites in the caudate and two classes of sites in the nucleus accumbens. Displacement of ['M'I]epidepride binding in the presence of p(NH]ppG by 7-OH-DPAT (A) was best RESULTS fit by assuming two classes of sites in the caudate and nucleus The of accumbens, but the proportion of high-affinity sites was small in Kinetic Experiments. determination optimal condi- caudate. Open symbols represent competitor alone and filled sym- tions for binding of [1251]epidepride to striatum indicated that represent competitor in presence of p[NH]ppG. binding was stable at 30°C. Equilibrium was reached by 60 bols min and remained stable for 180 min. All subsequent exper- iments were conducted at 30°C for 100 min. Analysis of the nucleus (Fig. 1A). In the nucleus accumbens the binding was saturation assays indicated that, as with binding in mem- best fit by assuming two classes of binding sites (Fig. 1B). branes (13), binding of [1251]epidepride to tissue sections was The high-affinity site was similar to that in the absence of best fit to a single-site model. The Kd for binding of [1251]epi- p[NH]ppG (IC50 of 392 nM) and accounted for 37% of the depride in caudate was 41.5 pM (SD of 5.2 pM); for nucleus sites. The low-affinity site was not different from that in the accumbens, 46 + 6.2 pM; and for inferior temporal lobe, 38.6 caudate (IC5o of27.18 ,uM) and accounted for 63% ofthe sites + 7.2 pM. The Bm. but not the Kd for [1251]epidepride binding (Fig. 1B). In the presence of p[NH]ppG, competition with in tissue sections did differ between regions. For the caudate, 7-OH-DPAT showed a best fit with a two-site model in both the Bm. was 129.5 ± 18 fmol/mg of protein; for the nucleus the (IC501 of 1.25 uM, IC502 of 0.35 nM) and accumbens, 165 + 24 fmol/mg protein; and for inferior nucleus accumbens (IC5oI of 910.7 nM, IC5o2 of 392 nM). temporal lobe, 13.9 + 7 fmol/mg protein. Thus, 7-OH-DPAT and quinpirole showed a greater than The ability of the agonists 7-OH-DPAT and quinpirole to 1000-fold selectivity for high-affinity sites compared with displace [12511epidepride in tissue sections ofcaudate nucleus low-affinity sites. In the presence of p[NH]ppG the agonists (Fig. 1A) or nucleus accumbens (Fig. 1B) was different in the a presence or absence of p[NH]ppG. Inhibition of the binding quinpirole and 7-OH-DPAT exhibited high affinity for of [1251]epidepride by quinpirole in the absence ofp[NH]ppG similar proportion of [125I]epidepride binding sites in the was best fit by assuming two classes of binding sites in the nucleus accumbens (31% to 36% of sites). Competition with caudate and nucleus accumbens (Fig. 1). In the caudate and domperidone for [125Iepidepride binding (IC50 of 1.59 nM) nucleus accumbens the high-affinity site (IC50 of 341 nM and also exhibited a best fit to one site in the caudate nucleus (Fig. 117 nM, respectively) represented 44% to 56% of the sites. 1A). In the nucleus accumbens a best fit was made by using The low-affinity site (IC50 of 11.21 ,uM and 4.80 ,uM, respec- a two-site model (domperidone IC501 of 2.99 nM, IC502 of tively, for caudate and nucleus accumbens) represented 43% 44.58 nM; Fig. 1B). Domperidone showed lower selectivity to 56% of the sites. In the presence of p[NH]ppG the than 7-OH-DPAT or quinpirole for the two sites but the inhibition of the binding of [1251]epidepride by quinpirole proportion of low-affinity sites was similar. These data indi- (IC50 of2.76 gM) showed the best fit to one site in the caudate cate that approximately 34% of the sites labeled by [1251]epi- Downloaded by guest on September 30, 2021 Pharmacology: Murray et al. Proc. Natl. Acad. Sci. USA 91 (1994) 11273

depride in the nucleus accumbens and a very small percent- binding of[1251]epidepride to D3-like receptors. At more caudal age in the caudate nucleus are D3-like. levels a high concentration of D3 receptors was evident Single-Point Autoradiographic Studies. The binding of throughout the GPi, as [125I]epidepride binding was almost [125I]epidepride (50 pM) to D2-like and D3-like receptors was completely displaceable by 7-OH-DPAT and only partially completely displaced by 300 nM raclopride or 5 ,uM (+)- displaceable by domperidone (Fig. 3D-F). The GPe displayed butaclamol. The concentration of D2-like receptors in regions a high concentration of D2-like receptors (Fig. 3 D-F). of brain was estimated by measuring the number of [125I]epi- In rostral regions ofthe ventral forebrain there were islands depride binding sites in the presence of50 nM 7-OH-DPAT, as of high concentrations of D2-like receptors (Fig. 3B) inter- it displaced 99.3% of the binding to the high-affinity (D3-like) mixed within islands ofD3-like receptors (Fig. 3C). Binding of sites and 3.8% ofthe binding to the low-affinity (D2-like) sites. [1251]epidepride to D3-like receptors (completely displaced by The obtained values were confirmed by estimating the number 7-OH-DPAT) occurred in specific regions of the basal fore- of [125I]epidepride binding sites to D3 receptors in the presence brain (Table 1). This included the ventral pallidum, islands of of 10 nM domperidone, as it displaced 81.4% of the binding to Calleja, septum, and nucleus basalis (Fig. 3 A-C). Within the the high-affinity (D2-like) sites and 18.3% ofthe binding to the amygdala D2-like receptors were highly expressed in the low-affinity (D3-like) sites. The ratio of D3-like to D2-like basomedial and basolateral nuclei (Fig. 4A). In contrast, the receptors varied significantly between regions of ventral fore- entire rostral-caudal extent of the amygdalostriatal transition brain (Table 1). Within the rostral caudate, the binding of nucleus and central nucleus ofthe amygdala was enriched with [125I]epidepride to D2-like receptors predominated over bind- D3-like receptors (Fig. 4B). The ratio of D3-like to D2-like ing to D3-like receptors by a wide margin. In contrast, in the receptors was also relatively high in both the medial compo- ventral striatum (nucleus accumbens and ventral putamen), nent of the and the ventral tegmental area D3-like receptors made up a significant proportion of the total (A10). The ratio greatly favored D2-like receptors in the number of [125I]epidepride binding sites. There was a rostral- substantia nigra (A9), A8 region, and nucleus raphe (Table 1). to-caudal gradient of D3-like receptors, with fewer in the The pharmacological properties of the binding of [125Ilepide- caudal ventral striatum. In both the rostral and caudal ventral pride to D2-like receptors in the frontal cortex, medial tem- striatum, D3-like receptors were concentrated in the AChE- poral lobe, and temporal cortex (13, 14) are D2-like and not poor striosomal compartment (Fig. 2 B and D). The AChE-rich D3-like ([1251]epidepride is largely displaced by domperidone). matrix compartment of the striatum is correlated with high amounts of [3H]spiroperidol binding to D2-like receptors (12). DISCUSSION [125I]Epidepride-labeled sites remaining in the presence of Since the original descriptions of the binding of agonists and 7-OH-DPAT showed enriched regions of D2-like receptors antagonists to D2 and D3 receptors (5), investigators have within the AChE-rich matrix. Binding of [125I]epidepride to reported smaller differences in the selectivity of the agonists D2-like or D3-like receptors differed along the rostral-to-caudal for the two receptors (15). This suggests that selective axis of the pallidum. At rostral levels there was almost a 1:1 displacement from D2 or D3 receptors in tissue sections of ratio of D2-like to D3-like receptors (Fig. 3 A-C). At interme- nonselective radioligands would be difficult to achieve. We diate levels the medial component ofthe GPi showed selective have previously determined the specificity of [1251]epidepride Table 1. Concentration of D2-like or D3-like receptors in various regions of ventral forebrain B.,, fmol/mg of protein Ratio Region Total D2 D3 D3/D2 Rostral striatum Caudate 134.3 ± 21 116.8 ± 18 17.2 ± 4 0.15 Nucleus accumbens Striosome 189.0 ± 18 79.1 ± 15 118.5 ± 11 1.50 Matrix 152.4 ± 11 101.2 ± 9 51.0 ± 7 0.50 Ventral putamen 174.6 ± 19 88.1 ± 14 94.6 + 10 1.07 Caudal striatum Caudate 162.7 + 16 155.3 ± 16 10.2 ± 7 0.06 Ventral putamen 132.5 ± 12 101.3 ± 13 35.6 ± 7 0.35 Pallidum External 63.7 ± 14 58.6 ± 17 8.1 ± 4 0.14 Internal 51.8 ± 15 4.4 ± 2 47.3 ± 11 10.75 Ventral 45.3 ± 10 4.5 ± 2 39.3 ± 10 8.73 Septal nucleus 109.8 ± 14 19.3 ± 4 89.4 ± 16 4.63 Islands of Calleja 99.3 ± 16 17.3 ± 3 73.6 ± 16 4.25 Nucleus basalis 91.8 ± 16 15.1 ± 3 76.1 ± 11 5.03 Substantia nigra Medial and A10 86.1 ± 23 25.8 ± 11 63.6 ± 17 2.46 Lateral (A9) 44.6 ± 15 36.7 ± 12 8.4 ± 7 0.23 A8-raphe 22.3 ± 9 21.1 ± 9 3.3 ± 4 0.16 Amygdala Basolateral 46.9 ± 9 38.8 ± 14 8.7 + 3 0.22 Central 58.2 ± 10 6.4 ± 2 51.1 ± 11 7.98 AST 69.3 ± 8 5.2 2 62.9 ± 9 12.09 The total Bma. values are for [1251]epidepride binding; Bnax values for D2 and D3 receptors are estimated from displacement experiments. Values are mean ± SD for a minimum of four subjects per region. AST, amygdalostriatal. Downloaded by guest on September 30, 2021 11274 Pharmacology: Murray et al. Proc. Natl. Acad. Sci. USA 91 (1994) D

E

C F \ *"...; .. a Or ;.~~~~~~~~~~~~~~~~~~~~Fg 't C v FIG. 2. Comparison of autoradiographic localization of the total FIG. 3. Autoradiographic localization of the total binding of binding of [1251]epidepride to D2 and D3 receptors (A) with that [12I]epidepride to D2 and D3 receptors (A, D). Comparison with observed in the presence of 10 nM domperidone to visualize D3-like localization observed in the presence of 7-OH-DPAT (blocked D3- receptors (B) in the human striatum. (C) Nonspecific binding of like receptors) to visualize D2-like receptors (B, E) and with that in [1251]epidepride in the presence of excess raclopride. (D) Adjacent the presence of10 nM domperidone to visualize D3-like receptors (C, section stained for AChE to visualize striosomal (AChE-poor) and E) in the ventral forebrain region (A-C) and pallidum (D-F). Binding matrix (AChE-rich) compartments. The arrow with asterisk in B of [125I~epidepride to D3-like receptors is enriched in islands of points to a D3-enriched region in the ventral putamen that is localized Calleja (large arrows) and septum (asterisks), as evidenced by to the AChE-poor zone (striosome) in the adjacent tissue section (D). displacement by 7-OH-DPAT (A, B) but to only a small extent by In contrast, AChE-poor zones in the caudate (arrow in D) do not have domperidone (C). Striatal islands enriched in D2 receptors are corresponding regions of enriched D3 receptors (arrow in B). evident in the same region (thin arrows, see B). The rostral globus pallidus displays similar numbers of D2-like (B) and D3-like (C) for autoradiographic analysis of D2-like receptors in several receptors. The caudal globus pallidus shows an enrichment ofD3-like human brain regions (13). In fact, in our previous study receptors in the globus pallidus internal (GPi) (large arrow) compared utilizing membranes derived from striatal regions (13), the with the globus pallidus external (GPe) (D-F). gp, Globus pallidus; displacement of [1251]epidepride binding with epidepride, Put, putamen. spiperone, butaclamol, flupenthixol, and clozapine showed a single class of binding sites. However, none of these com- The selectivity of the agonists quinpirole and 7-OH-DPAT pounds are able to selectively compete for binding of [125I]io- for D2- and D3-like receptor sites appears to be higher in dosulpride to the human D2 as compared with the human D3 tissue sections of human striatum than in CHO cells trans- receptor expressed in membranes of transfected CHO cells fected with the human D2 or D3 receptor. Landwehrmeyer (9, 10). In contrast, the agonists 7-OH-DPAT and quinpirole and associates (6) have provided similar results. The reason do show high selectivity for displacement of [125I]iodosul- for this is unclear, but it could reflect post-translational pride binding from the human D2 as compared with the human D3 receptor in the presence of GTP (9, 10). A_ In this study we examined the pharmacokinetics of the binding of [125I]epidepride to sites in the human striatum, using conditions originally determined for [1251]epidepride binding to membranes (13). Equilibrium was reached by 60 min and remained stable for 180 min at 30°C. The Kd established with saturation isotherms was approximately 40 pM (38-46 pM) and did not differ between regions of brain, indicating a similar affinity to D2-like and D3-like receptors. The distribution of D2 and D3 mRNAs within the striatum shows a high concentration of D3 receptor mRNA in the nucleus accumbens and very low amounts in the dorsal caudate, with a reverse gradient for the concentration of D2 receptor mRNA (6, 16). Thus, one would expect to be able to FIG. 4. Total binding of [125I]- identify a significant proportion of the binding of [125I]epide- epidepride to D2 and D3 receptors pride to D3-like receptors in the nucleus accumbens but (A) and that observed in the pres- almost exclusively to D2-like receptors in the dorsal caudate. ~ence~~~ of 10 nM domperidone to We demonstrated that there was a biphasic inhibition of visualize D3-like receptors (B) in and amnygdala. Binding of [12511epide- [125I]epidepride by domperidone, 7-OH-DPAT, quinpi- pride to 1)2-like receptors is almost role in the nucleus accumbens but not in the dorsal caudate totally displaced by domperidone nucleus. Additionally, excess p[NH]ppG produced a full in basolateral and basomedial nu- conversion to low-affinity sites for the agonists in the caudate clei (asterisks) but not in the nucleus (e.g., D2-like) but only a small extent of conversion amygdalostriatal transition nu- in the nucleus accumbens. cleus (arrows) of the amnygdala. Downloaded by guest on September 30, 2021 Pharmacology: Murray et al. Proc. Natl. Acad. Sci. USA 91 (1994) 11275 modification of these receptors in vivo that remains stable in can be extended to suggest that the D3 receptor preferentially tissue sections. Most importantly, the results show that in the mediates these actions of dopamine. The relevance for study- presence of excess p[NH]ppG 7-OH-DPAT, with greater ing potential alterations in the distribution and number of D3 than 1000-fold selectivity for D3-like as compared with D2- receptors in neuropsychiatric and neurodegenerative disor- like sites, could be used to completely mask D3-like receptors ders is now well established. to allow for quantification of D2-like receptors. In addition, [125I]Epidepride was a generous gift from Dr. Kim Neve (Depart- the antagonist domperidone could be used to partially mask ments of Psychiatry and Pharmacology, Oregon Health Sciences D2 receptors to confirm the anatomical distribution ofD3-like University and Department of Veterans Affairs Medical Center, receptors. The GPi and GPe can be used as examples, as they Portland). The compound 7-OH-DPAT was a generous gift from Dr. have complementary ratios of D2-like to D3-like receptors Hank Kung of the Department of Radiology, University of Pennsyl- (Fig. 3). In the GPi the binding of [125I]epidepride was vania School of Medicine. Brain tissue was obtained from the completely displaced by 7-OH-DPAT, and domperidone dis- Hospital ofthe University of Pennsylvania (J. Trojanowski, Director the binding to an extent consistent with binding to the of Medical Pathology), the Sun Health Research Institute (Dr. Joe placed Rogers, Director, Sun City, AZ), and the University of California D3 receptor (18%). The reverse was obtained for the GPe: Irvine Medical Center Organ and Tissue Bank (graciously provided binding was not displaceable by 7-OH-DPAT but was signif- by Dr. C. Cottman). This research was supported by an award from icantly reduced by domperidone. Scottish Rite Benevolent Foundation's Research Pro- Our results support the hypothesis that subtypes of the gram, Northern Masonic Jurisdiction and by U.S. Public Health dopamine receptor family are relatively segregated to specific Service Grants MH 43852, MH 43880, AG 09215, and AG 10124 circuits (17). For example, while the expressing (Alzheimer Disease Center Core). A.M.M. was supported by a grant mRNA for Di, D2, and D3 receptors are largely intermingled from the National Parkinson Foundation (Miami). in the primate striatum (6, 16), there appears to be a func- 1. Civelli, O., Bunzow, J. R., Grandy, D. K., Zhou, Q. Y. & Van Tol, tional compartmentalization of the receptors measured at H. H. M. (1991) Eur. J. Pharmacol. 207, 277-286. several levels. First, mRNA encoding the D2 receptor is 2. Levesque, D. L., Diaz, J., Pilon, C., Martres, M.-P., Giros, B., higher in concentration in the dorsal than ventral striatum, Souil, E., Schott, D., Morgt, J.-L., Schwartz, J.-C. & Sokoloff, P. reverse holds true for receptor mRNA (6, 16). (1992) Proc. Nat!. Acad. Sci. USA 89, 8155-8159. whereas the D3 3. Mansour, A., Meador-Woodruff, J. H., Bunzow, J. R., Civelli, O., Second, the densities of the receptors, as measured by Akil, H. & Watson, S. J. (1990) J. Neurosci. 10, 2587-2600. radioligand binding, are relatively segregated to compart- 4. Van Tol, H. H. M., Bunzow, J. R., Guan, H.-C.,Sunahara, R. K., ments within the striatum. The D2 receptor is enriched in the Seeman, P., Niznik, H. B. & Civelli, 0. (1991) Nature (London) matrix compartment with a dorsolateral-to-medioventral gra- 350, 610-614. dient (ref. 12; this study). The Di receptor is enriched in the 5. Schwartz, J.-C., Levesque, D., Martres, M.-P. & Sokoloff, P. (1993) in Clin. Neuropharmacol. 16, 295-314. striosomal compartment, particularly the dorsal caudate 6. Landwehrmeyer, B., Mengod, G. & Palacios, J. M. (1993) Mol. nucleus (18). In contrast, the D3 receptor is enriched in the Brain Res. 18, 1878-1892. striosomal compartment of the ventral striatum. Third, the 7. Murray, A. M., Ryoo, H. & Joyce, J. (1992) Eur. J. Pharmacol. 227, -containing neurons that give rise to the striato- 443-445. pallidal pathway to the GPe are largely segregated with the D2 8. Mach, R. H., Luedtke, R. R., Unswoth, C. D., Boundy, V. A., receptor (19, 20). In contrast, the -positive neu- Nowak, P. A., Scripko, J. G., Elder, S. T., Jackson, J. R., Hoff- man, P. L., Evora, P. H., Rao, A. V., Molinoff, P. B., Childers, rons that project to the GPi and ventral tegmental area S. R. & Ehrenkaufer, R. L. (1993) J. Med. Chem. 36, 3707-3720. express the Di receptor (19, 20). Our results further suggest 9. Sokoloff, P., Andrieux, M., Besancon, R., Pilon, C., Martres, that the pathway from the ventral striatum to the ventral M.-P., Giros, B. & Schwartz, J. C. (1992) Eur. J. Pharmacol. 225, pallidum, GPi, and ventral tegmental area correlate with the 331-337. D3 receptor. This is particularly relevant, as the distribution 10. Freedman, S. B., Patel, S., Marwood, R., Emms, F., Seabrook, forebrain is consistent with localiza- G. R., Knowles, M. R. & McAllister, G. (1994) J. Pharmacol. Exp. of D3 mRNA in human Ther. 268, 417-426. tion of the D3 receptor postsynaptically on striatal neurons 11. McGonigle, P., Neve, K. A. & Molinoff, P. B. (1986) Mol. Phar- and not presynaptically on dopamine terminals (6). Finally, macol. 30, 329-337. distinct populations of dopaminergic neurons within the 12. Joyce, J. N., Sapp, D. W. & Marshall, J. F. (1986) Proc. Nat!. ventral mesencephalon innervate different territories of stri- Acad. Sci. USA 83, 8002-8006. atum (21). Hence, the different compartments ofthe striatum, 13. Joyce, J. N., Janowski, A. & Neve, K. A. (1991) J. Pharmacol. Exp. Ther. 253, 1253-1263. and their striatopallidal and striatonigral efferents, would be 14. Goldsmith, S. & Joyce, J. N. (1994) Hippocampus 4, 1-20. influenced by different dopaminergic systems mediated, in 15. Chio, L., Lajines, M. E. & Huff, R. M. (1994) Mol. Pharmacol. 45, part, by different dopamine receptors. 51-60. In addition to this level of compartmentalization, there is a 16. Rappaport, M. S., Sealfon, S. C., Prikhozhan, A., Huntley, G. W. separation of D3-like receptors to the ventral forebrain me- & Morrison, J. H. (1993) Brain Res. 616, 242-250. solimbic dopaminergic system and D2-like receptors to the 17. Joyce, J. N. & Murray, A. (1994) in Dopamine Receptors and Transporters, ed. Niznik, H. B. (Dekker, New York), pp. 345-382. mesocortical and mesohippocampal dopaminergic system (13, 18. Besson, M. J., Graybiel, A. M. & Nastuk, M. A. (1988) Neuro- 14, 17). The septum, islands of Calleja, and neurons of the science 26, 101-119. nucleus basalis express D3 receptors and D3 receptor mRNA 19. Gerfen, C. R., Engber, T. M., Mahan, L. C., Susel, Z., Chase, (ref. 6; this study) and are innervated by the mesolimbic T. N., Monsma, F. J., Jr., & Sibley, D. R. (1990) Science 250, dopaminergic system (22), whereas islands of striatal neurons 1429-1432. ventral forebrain that express receptors 20. Graybiel, A. M. (1984) Ciba Found. Symp. 107, 114-149. within the D2-like and, 21. Jimenez-Castellanos, J. & Graybiel, A. M. (1987) Neuroscience 23, presumably, D2 mRNA (ref. 16; this study) are likely to be 223-242. innervated by the A8 cell group (21). Further, regions of the 22. Fallon, J. H. & Loughlin, S. E. (1985) in The Rat Nervous System, cortex and hippocampus with relatively dense innervation by Forebrain andMidbrain, ed. Paxinos, G. (Academic, Orlando, FL), dopaminergic afferents (23) show high levels ofD2 (or Di) and Vol. 1, pp. 353-374. not D3 receptors (13, 14, 17). Nonetheless, ventral forebrain 23. Gaspar, P., Stepniewska, I. & Kaas, J. H. (1992) J. Comp. Neurol. to 325, 1-21. cell groups that provide widespread innervation 24. McGeer, P. L., McGeer, E. G., Suzuki, J., Dolman, C. E. & Nagai, the cortex and hippocampus would contain D3 receptors (24). T. (1984) Neurology 34, 741-745. Hence, the notion that the mesolimbic dopaminergic pathway 25. Mogenson, G. J., Yang, C. R. & Yim, C. Y. (1988)Ann. N. Y. Acad. acts as an interface between motor and nonmotor systems (25) Sci. 537, 86-100. 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