[3H]SCH 23390 binding to D1 dopamine receptors in the basal ganglia of the cat and primate: delineation of striosomal compartments and pallidal and nigral subdivisions

Modulation of dopaminergic terminal excitability by D1 selective agents: further characterization

We have previously shown that stimulation of striatal D1 receptors affects dopaminergic nigrostriatal terminal excitability, which is thought to be an index of biophysical events resulting from the activation of receptors on the presynaptic membrane. The experiments presented here further examine the locus and bases of these D1 effects in the rat. We now report that striatal administration of the D1 receptor selective antagonist R-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazapine+ ++-7-ol-HCl (SCH 23390) produces a paradoxical agonist-like decrease in dopaminergic terminal excitability. This effect is blocked by pretreatment with the dopamine synthesis inhibitor, alpha-methyl-paratyrosine, suggesting that the action of SCH 23390 is dependent upon endogenous dopamine. Further, haloperidol pretreatment also prevents the SCH 23390-induced decrease in terminal excitability, confirming that dopamine, acting through a dopamine receptor, is responsible for this agonist-like action. Striatal application of the active R-(+) enantiomer of the dopaminergic D1-selective agonist 1-phenyl-2,3,4,5-tetrahydrol-(1H)-3-benzazepine-7,8-diol-HCl (R-SKF 38393) decreases terminal excitability in the alpha-methyl-paratyrosine pretreated animal, indicating that dopamine is not required for the agonist action. In an effort to ascertain the presynaptic or postsynaptic location of these actions, an extensive destruction of postsynaptic neurons in the neostriatum was produced by local administration of the neurotoxin, kainic acid. It was observed that the neurotoxin-induced neostriatal neuronal loss did not disrupt the action of R-SKF 38393 nor its reversal by SCH 23390.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopaminergic system mediates only delta-opiate inhibition of endogenous acetylcholine release evoked by glutamate from rat striatal slices

In order to study the role of the dopaminergic system in the mu- or delta-opioid inhibition of endogenous acetylcholine release evoked by glutamate, we blocked the dopaminergic transmission with dopaminergic antagonists and/or 6-hydroxydopamine lesions. In all these experimental conditions we show that dopaminergic antagonists by themselves could not modify the glutamate-evoked acetylcholine release, and the selective D1 antagonist (SCH 23390) was unable to modify the mu- or delta-opioid inhibition of glutamate-evoked acetylcholine release. However, in the non-lesioned animals and in the contralateral striata to 6-hydroxydopamine lesions, D2 antagonists (haloperidol or sulpiride, 10 microM) prevented the effects of delta-opiate agonists ([D-Ala2, D-Leu5]enkephalin, 1 microM and [D-Pen2, D-Pen5]enkephalin, 0.1 microM), but not the effects of mu-opiate agonists (morphine or [D-Ala2, Gly(ol)5]enkephalin, 1 microM). Furthermore, [D-Ala2, D-Leu5]enkephalin inhibition of glutamate-evoked acetylcholine release was prevented by D2 antagonists in a concentration-dependent manner. Instead, in the 6-hydroxydopamine-lesioned side, while [D-Ala2, D-Leu5]enkephalin (1 microM) inhibition of glutamate-evoked acetylcholine release was completely abolished, morphine (1 microM) inhibition remained unchanged. We conclude that the inhibition of glutamate-evoked endogenous acetylcholine release by delta-opiate agonists, unlike mu-opiate agonists, depends on dopaminergic terminals and D2 receptors. Furthermore, these results suggest that the inhibition by delta-opiate agonists could be the result of dopamine release from dopaminergic terminals and its action on D2 receptors.

Muscarinic and dopaminergic receptor subtypes on striatal cholinergic interneurons

Unilateral stereotaxic injection of small amounts of the cholinotoxin, AF64A, caused minimal nonselective tissue damage and resulted in a significant loss of the presynaptic cholinergic markers [3H]hemicholinium-3 (45% reduction) and choline acetyltransferase (27% reduction). No significant change from control was observed in tyrosine hydroxylase or tryptophan hydroxylase activity; presynaptic neuronal markers for dopamine- and serotonin-containing neurons, respectively. The AF64A lesion resulted in a significant reduction of dopamine D2 receptors as evidenced by a decrease in [3H]sulpiride binding (42% reduction) and decrease of muscarinic non-M1 receptors as shown by a reduction in [3H]QNB binding in the presence of 100 nM pirenzepine (36% reduction). Saturation studies revealed that the change in [3H]sulpiride and [3H]QNB binding was due to a change in Bmax not Kd. Intrastriatal injection of AF64A failed to alter dopamine D1 or muscarinic M1 receptors labeled with [3H]SCH23390 and [3H]pirenzepine, respectively. In addition, no change in [3H]forskolin-labeled adenylate cyclase was observed. These results demonstrate that a subpopulation of muscarinic receptors (non-M1) are presynaptic on cholinergic interneurons (hence, autoreceptors), and a subpopulation of dopamine D2 receptors are postsynaptic on cholinergic interneurons. Furthermore, dopamine D1, muscarinic M1 and [3H]forskolin-labeled adenylate cyclase are not localized to striatal cholinergic interneurons.

Amphetamine and cocaine induce drug-specific activation of the c-fos gene in striosome-matrix compartments and limbic subdivisions of the striatum

Amphetamine and cocaine are stimulant drugs that act on central monoaminergic neurons to produce both acute psychomotor activation and long-lasting behavioral effects including addiction and psychosis. Here we report that single doses of these drugs induce rapid expression of the nuclear proto-oncogene c-fos in the forebrain and particularly in the striatum, an extrapyramidal structure implicated in addiction and in long-term drug-induced changes in motor function. The two drugs induce strikingly different patterns of c-fos expression in the striosome-matrix compartments and limbic subdivisions of the striatum, and their effects are pharmacologically distinct, although both are sensitive to dopamine receptor blockade. We propose that differential activation of immediate-early genes by psychostimulants may be an early step in drug-specific molecular cascades contributing to acute and long-lasting psychostimulant-induced changes in behavior.

Intrastriatal grafts derived from fetal striatal primordia: II. Reconstitution of cholinergic and dopaminergic systems

Reconstitution of striatal cholinergic and dopaminergic systems was studied in intrastriatal grafts derived from embryonic day 15 rat striatal primordia and implanted into adult host rats in which unilateral ibotenic acid lesions had previously been made in the striatum. Histochemical, immunohistochemical, and ligand binding autoradiographic techniques were applied to analyze different constituents of these two systems and to study their locations relative to each other in grafts allowed to grow for 9-17 months following transplantation. For the cholinergic system, a modular organization was found in the striatal grafts with stains for choline acetyltransferase and acetylcholinesterase, respectively the synthetic and degradative enzymes for cholinergic neurons; by autoradiographic [3H]hemicholinium binding, specific for high affinity choline uptake sites associated with cholinergic terminals; and by autoradiographic [3H]pirenzepine binding, selective for M1 receptors. For the dopaminergic system, a comparable modular organization was found in the grafts by immunostaining for tyrosine hydroxylase, the catecholamine synthetic enzyme; by autoradiographic [3H]mazindol binding for dopamine uptake sites; and by [3H]SCH23390 binding for dopamine D1 receptors and [3H]sulpiride binding for dopamine D2 receptors. The results indicate that the distributions of the cholinergic and dopaminergic markers in striatal grafts are in close anatomical register. These markers for intracellular and membrane-associated components of the cholinergic and dopaminergic systems were preferentially localized in the acetylcholesterase-rich patches of the grafts in which cortical and thalamic fibers have also been found in striatal grafts, and in which output neurons projecting to the pallidum are located. This anatomical correlation suggests that the substrates for cholinergic-dopaminergic interactions typical of the normal striatum may be reinstated in the grafts both in relation to efferent neurons establishing connections with the host brain that are typical of normal striatofugal connections, and in relation to major afferent fiber systems from the host brain originating in regions known to project densely to the normal striatum. Accordingly, the cholinergic and dopaminergic systems in such grafts may regulate the functional influence of the grafts on the behavior of host animals.

Autoradiographic studies in animal models of hemi-parkinsonism reveal dopamine D2 but not D1 receptor supersensitivity. II. Unilateral intra-carotid infusion of MPTP in the monkey (Macaca fascicularis)

The selective dopaminergic antagonist ligands [3H]SCH 23390 and [3H]sulpiride were used to reveal autoradiographically dopamine D1 and D2 receptors, respectively, in brain sections from monkeys which had received unilateral intracarotid infusions of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), causing loss of dopamine-containing neurones of the substantia nigra pars compacta. The monkeys developed hemi-parkinsonian symptoms (tremor, bradykinesia) in limbs contralateral to the side of the toxin infusion. Administration of apomorphine (0.05-0.25 mg/kg) caused contralateral rotational behaviour, and reversal of the parkinsonian symptoms. Loss of forebrain dopaminergic terminals was assessed autoradiographically using [3H]mazindol to label dopamine uptake sites. A reduction in these sites of 97% (mean brain value) in the caudate nucleus, and 91% in the putamen, as compared with binding values from untreated control monkeys, was accompanied by a significant increase in the binding of [3H]sulpiride (D2) in these structures. In contrast, in the same animals there was no similar increase in [3H]SCH 23390 binding to D1 receptors in the denervated areas. These results suggest that in the parkinsonian brain, where the dopaminergic innervation of the caudate nucleus and putamen has been lost, D2 receptors may be more susceptible than D1 receptors to changes, revealed here as an increase in [3H]sulpiride binding sites.

Striosomal organization of cholinergic and dopaminergic uptake sites and cholinergic M1 receptors in the adult human striatum: a quantitative receptor autoradiographic study

The distribution of cholinergic pre- and postsynaptic markers and dopaminergic presynaptic markers was analyzed in the adult human striatum, using quantitative receptor autoradiography. The distribution of the different binding sites indicates that cholinergic and dopaminergic uptake sites display a striosomal organization, with a higher binding site density in the striatal matrix. M1 muscarinic cholinergic receptor distribution parallels the distribution of cholinergic presynaptic markers. Our data show that cholinergic and dopaminergic terminals, and M1 receptors are enriched in the matrix of the adult human striatum.

Differential modulation of striatonigral dynorphin and enkephalin by dopamine receptor subtypes

Previous studies indicate that dopaminergic transmission inhibits the biosynthesis of enkephalin and stimulates that of dynorphin in the striatonigral pathway of intact rat. The purpose of this study was to determine which dopamine (DA) receptor subtype(s) mediate the modulatory actions of DA. We measured striatal and nigral levels of enkephalin and dynorphin in: (1) intact rats repeatedly injected with D1 (SKF-38393, 5 mg/kg, i.p.) or D2 (LY-171555, 1 mg/kg, i.p.) agonists, alone or in combination, (2) 6-hydroxydopamine (6-OHDA)-lesioned rats repeatedly injected with the same D1 or D2 agonists, and (3) intact rats repeatedly injected with D1 (SCH-23390, 0.05 mg/kg, s.c.) or D2 (sulpiride, 100 mg/kg, s.c.) antagonists, given alone or in combination with the mixed D1/D2 agonist apomorphine (5 mg/kg, i.p.). Repeated injections of the D1 agonist to intact rats (twice daily for 7 days) produced a small but not statistically significant increase in striatal levels of dynorphin; similar treatment with the D2 agonist did not affect dynorphin levels at all. Combined treatments with D1 and D2 agonists did not potentiate the effect of the D1 agonist. 6-OHDA lesions of the nigrostriatal DA pathway alone decreased the level of dynorphin in both the striatum and substantia nigra. However, repeated D1 agonist, but not D2, injections not only reversed the decrease in dynorphin levels, but caused a significant increase above control levels. In intact rats, repeated injections of the D1 or D2 antagonist alone failed to alter the levels of dynorphin, but the D1 antagonist, not the D2 antagonist, attenuated the apomorphine-induced increase in striatal dynorphin.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional distribution of cholecystokinin binding sites in macaque basal ganglia determined by in vitro receptor autoradiography

Cholecystokinin binding sites were labeled with [3H]cholecystokinin-8, [125I]cholecystokinin-33, and [125I]cholecystokinin-8 in major structures of macaque basal ganglia by in vitro receptor autoradiography. Analysis of autoradiograms revealed areas of heavy cholecystokinin binding in the neostriatum and substantia nigra that were set off, often quite sharply, from the adjacent globus pallidus and subthalamic nucleus where labeling was, by contrast, very light. Heavy label characterized the ventromedial and posterior parts of the caudate nucleus and adjacent putamen, binding was of moderate intensity in central areas of these regions, while, the dorsolateral margin of the head of the caudate and precommissural putamen, the dorsolateral one-third of the body of the caudate, and all but the most medial and ventral portions of the posterior putamen lateral to the pallidum were sparsely labeled. The pattern of cholecystokinin binding within the neostriatum was mottled; patches of reduced label stood out from the background of more prominent binding. However, those patches were only imperfectly correlated with the striosomal organization of both the caudate nucleus and putamen as revealed by acetylcholinesterase staining. Cholecystokinin binding in the substantia nigra was also intricately patterned. Moderately dense, vertically orientated bands of label were found in the dorsal one-third to half of the pars reticulata, providing a marked contrast to the near background levels in the ventral pars reticulata and overlying pars compacta. The present study shows that heavy cholecystokinin binding is confined to particular areas within the primate basal ganglia; the pattern of label within the substantia nigra and neostriatum can be linked to intrinsic and afferent connections of these structures. The confinement of binding sites to the dorsal pars reticulata suggests an association with dendrites of pars compacta neurons which invade this region; this interpretation is consistent with recent evidence of depletion of nigral cholecystokinin binding sites in macaques following chemical lesion of dopaminergic cells of the par compacta. In the neostriatum the distribution of binding shows overlap with its topographically organized corticostriatal innervation; portions of heavily labeled striatum coincide with regions innervated by association cortex of the frontal and temporal lobes, whereas regions of diminished binding correspond to areas innervated mainly by sensory and motor cortex. These latter findings suggest that cholecystokinin may have a particularly strong influence on cognitive aspects of striatal function.

Microtopography of D1 dopaminergic binding sites in the human substantia nigra: an autoradiographic study

The autoradiographic distribution of D1 dopaminergic binding sites was studied in the human ventral mesencephalon using the D1 antagonist [3H]SCH 23390. [3H]SCH 23390 binding was characterized by a single class of sites with a Kd of 2.5 nM and a Bmax of 31 fmol/mg of tissue. The density of [3H]SCH 23390 binding sites was high in the substantia nigra, moderate in the ventral tegmental area and low in the peri- and retrorubral field (catecholaminergic region A8). Binding densities were similar in pars compacta and pars reticulata of the substantia nigra, except for a peak value of high [3H]SCH 23390 in the pars reticulata, at a level just ventral to a zone of hyperdensity of melanized dopaminergic neurons in the pars compacta. The anatomical organization of the human ventral mesencephalon was analysed on adjacent sections stained for acetylcholinesterase histochemistry and tyrosine hydroxylase, substance P, dynorphin B, somatostatin and methionine-enkephalin immunohistochemistry, respectively. The similarity in distribution of [3H]SCH 23390 binding sites and substance P or dynorphin B immunoreactivity suggests that D1 binding sites are mainly located on the striatonigral projections. In accordance with these results: (1) the density of [3H]SCH 23390 binding sites was reduced in the substantia nigra of a patient with Huntington's chorea, a disease associated with a degeneration of striatonigral neurons; (2) the density of [3H]SCH 23390 binding sites was unaffected in the substantia nigra of a patient with Parkinson's disease, a disorder characterized by a marked loss in nigral tyrosine hydroxylase-positive neurons. [3H]SCH 23390 binding sites showed a characteristic, heterogeneous distribution within the human ventral mesencephalon, confirming data obtained in other species. The preferential localization of D1 dopamine receptors on striatonigral projections in human brain suggests that pharmacological manipulation of these receptors modulates the activity of striatonigral pathways, thereby affecting the various outputs of the nigral complex.

Co-expression of neuropeptides in the cat's striatum: an immunohistochemical study of substance P, dynorphin B and enkephalin

The expression of tachykinin-like and opioid-like peptides was studied in medium-sized neurons of the caudate nucleus in tissue from adult cats pretreated with colchicine. Two methods, a serial thin-section peroxidase-antiperoxidase technique and a two-fluorochrome single-section technique, were applied. Quantitative estimates were made mainly with the peroxidase-antiperoxidase method. The numbers of neurons expressing substance P-like, dynorphin B-like, and enkephalin-like immunoreactivity were recorded in regions identified, respectively, as striosomes and extrastriosomal matrix. Striosomes were defined by the presence of clustered substance P-positive and dynorphin B-positive neurons and neuropil. Tests for the co-existence of enkephalin-like peptide and glutamate decarboxylase-like immunoreactivity were also made with the peroxidase-antiperoxidase method. Co-expression of substance P-like and dynorphin B-like immunoreactivities was the rule both in striosomes and in the matrix. In striosomes, substance P-like immunoreactivity was found in 96% of dynorphin B-immunoreactive neurons, and in the matrix 89% of dynorphin B-positive cells contained substance P-like immunoreactivity. Substance P/dynorphin B-positive neurons corresponded to over half (57%) of the neurons in striosomes but only 39% of the neurons in the matrix. Both in the matrix and in striosomes, about two-thirds of all neurons (63% and 65%, respectively) were identified as enkephalin-positive. Among all substance P/dynorphin B-positive medium-sized neurons, 76% also contained enkephalin-like antigen. The enkephalin-positive neurons characterized by triple peptide co-existence (enkephalin/substance P/dynorphin B) represented a mean of 63% of striosomal enkephalin-positive neurons (41% of all striosomal neurons) and 35% of matrical enkephalin-positive neurons (26% of all matrical neurons). Finally, nearly all enkephalin-positive neurons were immunoreactive for glutamate decarboxylase, and therefore probably GABAergic, but only about half the glutamate decarboxylase-positive population was enkephalin-immunoreactive. These findings suggest that neuropeptides from three distinct precursors may be co-localized in single medium-sized neurons in the striatum, and that the differential patterns of co-expression of substance P-like, dynorphin B-like, and enkephalin-like peptides may confer functional specializations upon subpopulations of GABAergic neurons giving rise to the efferent projections of the striatum. The linked expression of substance P-like and dynorphin B-like peptides in single neurons both in striosomes and matrix suggests that some regulatory mechanisms controlling peptide expression apply regardless of compartment.(ABSTRACT TRUNCATED AT 400 WORDS)

Dopamine high-affinity transport site topography in rat brain: major differences between dorsal and ventral striatum

Investigations were conducted to determine the topography of the high-affinity dopamine uptake process within the rat striatum. [3H]Dopamine uptake into crude synaptosomes prepared from micropunch samples was found to be two- to three-fold higher in dorsal caudate-putamen relative to nucleus accumbens septi. In contrast, the concentrations of dopamine in the two regions were equivalent. The recognition site associated with high-affinity dopamine uptake was labeled using [3H]mazindol, and the binding of this ligand was also found to be two- to three-fold higher in homogenates from dorsal caudate-putamen samples relative to nucleus accumbens septi. Regional differences in uptake of [3H]dopamine or binding of [3H]mazindol were shown to be due to variations in Vmax or Bmax, not to differences in apparent affinity. Autoradiography of [3H]mazindol binding in rat striatum revealed a decreasing density of the site along the dorsal-to-ventral axis, with the highest binding occurring in the dorsolateral caudate-putamen, lower binding in the ventral caudate-putamen, and lowest levels in the septal pole of the nucleus accumbens septi. Quantification showed that the extent of this gradient was two-fold. Further autoradiographic studies revealed less striatal heterogeneity in the pattern of binding of [3H]ketanserin, another radioligand associated with the striatal dopaminergic innervation but not linked to the dopamine uptake process of the plasma membrane. The findings suggest that the dopaminergic fibers of the ventral striatum, especially the medial nucleus accumbens septi, may be relatively lacking in their capacity for dopamine uptake following its release. This organization may result in regional differences in the time-course of of extraneuronal dopamine following transmitter release and may render the dopamine-containing terminals of the ventral striatum less susceptible to the degenerative influences of neurotoxins that are incorporated by the high-affinity dopamine uptake process.

Quantitative autoradiographical analysis of the age-related modulation of central dopamine D1 and D2 receptors

Quantitative autoradiography of [3H]SCH 23390 and [3H](-)-sulpiride binding was performed in the brain of rats of various ages (3, 11 and 24 months) in order to study the changes in D1 and D2 receptor density with age. Binding of [3H]SCH 23390 in the caudate-putamen decreased progressively and markedly at rostral levels in 11- and 24- compared with 3-month-old rats (max. decrease -63%) while at caudal levels significant decrease was observed only in 24-month-old rats. [3H](-)-Sulpiride binding progressively decreased during aging in the caudate-putamen at rostral levels and the decrease was more pronounced laterally (-70% at 24 months), while at caudal levels no significant decrease was observed. D1 and D2 binding sites also decreased in the nucleus accumbens and olfactory tubercle of aged rats, while in the substantia nigra only the D1 receptors appeared to be modified with aging. No change was found in the entopeduncular nucleus, amygdala, frontoparietal, suprarinal-prefrontal and anterior cingulate cortex. The results indicate that the age-associated decrease of D1 and D2 receptors is not widespread, being confined to dopaminergic areas with high density of dopamine receptors.

Distinct presynaptic control of dopamine release in striosomal and matrix areas of the cat caudate nucleus

By use of a sensitive in vitro microsuperfusion method, the cholinergic prsynaptic control of dopamine release was investigated in a prominent striosome (areas poor in acetylcholinesterase activity) located within the core of cat caudate nucleus and also in adjacent matrix area. The spontaneous release of [3H]dopamine continuously synthesized from [3H]tyrosine in the matrix area was found to be twice that in the striosomal area; the spontaneous and potassium-evoked releases of [3H]dopamine were calcium-dependent in both compartments. With 10(-6) M tetrodotoxin, 5 x 10(-5) M acetylcholine stimulated [3H]dopamine release in both striosomal and matrix areas, effects completely antagonized by atropine (10(-6) M), thus showing the involvement of muscarinic receptors located on dopaminergic nerve terminals. Experiments without tetrodotoxin revealed a more complex regulation of dopamine release in the matrix: (i) In contrast to results seen in the striosome, acetylcholine induced only a transient stimulatory effect on matrix dopamine release. (ii) Although 10(-6) M atropine completely abolished the cholinergic stimulatory effect on [3H]dopamine release in striosomal area, delayed and prolonged stimulation of [3H]dopamine release was seen with atropine in the matrix. The latter effect was completely abolished by the nicotinic antagonist pempidine (10(-5) M). Therefore, in the matrix, in addition to its direct (tetrodotoxin-insensitive) facilitatory action on [3H]dopamine release, acetylcholine exerts two indirect (tetrodotoxin-sensitive) opposing effects: an inhibition and a stimulation of [3H]dopamine release mediated by muscarinic and nicotinic receptors, respectively.

Dopamine uptake sites in the striatum are distributed differentially in striosome and matrix compartments

A major mechanism of neurotransmitter inactivation at catecholaminergic synapses is reuptake of released transmitter at high-affinity uptake sites on presynaptic terminals. We have analyzed the anatomical distribution of site-selective ligand binding for dopamine uptake sites in the striatum of rat, cat, and monkey. We report here that desipramine-sensitive [3H]mazindol binding sites have highly heterogeneous distributions in the dorsal and the ventral striatum. In the caudate nucleus of cat and monkey, [3H]mazindol binding observes striosomal ordering, being reduced in striosomes and heightened in the extrastriosomal matrix. Some local heterogeneity appears in the ventral caudoputamen of the rat. Different subdivisions of the nucleus accumbens also have different binding levels. These findings suggest that some functional effects of psychoactive drugs, such as cocaine, that bind to the dopamine-uptake complex could be related to the distribution of these specific uptake sites. The findings also raise the possibility that these distributions could result in selective neuronal vulnerability to neurotoxins, such as 1-methyl-4-phenylpyridine (MPP+), that depend on the dopamine-uptake complex for entry into neurons.

Distinct nigrostriatal projection systems innervate striosomes and matrix in the primate striatum

Mesostriatal projections were labeled in 11 squirrel monkeys by injecting the anterograde tracer, [35S]methionine, into different parts of the dopamine-containing A8-A9-A10 cell complex of the midbrain. Two strikingly different compartmental patterns of mesostriatal projection were found. Fields of dense labeling in both the caudate nucleus and the putamen, interrupted by pockets of sparse labeling, were observed with deposits involving cell group A8, cell group A10 and/or the dorsally situated 'pars mixta' of the substantia nigra. Where striosomes could be identified as such in adjoining histochemically stained sections, the sparsely labeled zones were aligned with them. By contrast, a pattern of focally dense labeling in the caudate nucleus and putamen, with much weaker labeling surrounding the densely labeled zones, was found with injection sites centered in the horizontal band and associated ventrally extending fingers of the substantia nigra pars compacta. Many of the pockets of heightened labeling could be shown to correspond to histochemically defined striosomes. These compartmental patterns were identified both in the caudate nucleus and in the putamen. We conclude that the A8-A9-A10 cell complex of the primate contains spatially distinct subdivisions with preferential projections directed, respectively, toward the striosome and matrix compartments of the striatum.

Microinjections of Sch-23390 into the ventral tegmental area and substantia nigra pars reticulata attenuate the development of sensitization to the locomotor activating effects of systemic amphetamine

Pre-exposure of rats to systemic injections of D-amphetamine sulfate in the presence of bilateral injections of Sch-23390 (0.5 or 1.0 micrograms/side) into the ventral tegmental area (VTA) attenuated the acute locomotor effects of amphetamine and blocked the development of sensitization to amphetamine in a test when only amphetamine was administered, in a dose-dependent manner. Similar, but less potent, effects were observed following injections into substantia nigra pars reticulata. These findings suggest that dopamine released from somatodendritic regions brings about changes in local circuitry in the VTA that underlie the development of sensitization to amphetamine, and that Sch-23390 acts at D1 receptors in these regions to block these changes.

The distribution of neurotensin receptors and acetylcholinesterase in the human caudate nucleus: evidence for the existence of a third neurochemical compartment

The distribution of neurotensin receptors in the human caudate nucleus was studied using autoradiographic methods following in vitro labelling of cryostat sections with [3H]neurotensin, and the pattern of receptor labelling was compared to the distribution of acetylcholinesterase (AChE) staining in adjacent sections. A heterogeneous pattern of neurotensin receptors was found in the caudate nucleus. Patches of low receptor density aligned with the AChE-poor striosomes, regions of moderate receptor density corresponded with the AChE-rich matrix zone, and annular regions of high receptor density aligned with the AChE-negative border zone lying between the AChE-poor striosome and the AChE-rich matrix compartments. These results suggest the existence of 3 neurochemical compartments within the human caudate nucleus.

Distribution of dopamine D-2 receptors in the rat striatal complex and its comparison with acetylcholinesterase

The distribution of D-2 dopamine receptors in the rat striatal complex was studied with autoradiography after specific in vivo labeling with the dopamine agonist [3H]N-n-propylnorapomorphine and subsequent irreversible fixation. This labeling technique allows the visualization of D-2 receptors at the cellular level by light microscopic emulsion autoradiography. During the preparation of emulsion autoradiograms, the recovery of the label was 75%, the specific and the aspecific label being equally affected. The distribution of label before and after the loss of radioactive label occurred, did not show differences. In rat neostriatum, dopamine D-2 receptors are not homogeneously distributed: in the caudate-putamen the density is laterally higher than medially. Moreover, there exists a mosaic-like pattern of receptor density. In the ventral striatum, comprising the fundus striati, nucleus accumbens septi and olfactory tubercle, the receptor density is lower than in the caudate-putamen, except for the core regions in the islands of Calleja and the rim of these islands, which contain high (as high as the lateral caudate-putamen) and a moderate density of receptors, respectively. In caudate-putamen and lateral nucleus accumbens it appeared that the intensity of acetylcholinesterase staining parallels more or less the distribution of dopamine D-2 receptors. In medial nucleus accumbens and in olfactory tubercle, the high intensity of acetylcholinesterase is not paralleled by a high D-2 receptor labeling density. This receptor labeling density does not seem to be matched by differences in densities of medium-sized neuronal cell bodies.

Compartmental origins of striatal efferent projections in the cat

Injections of the retrograde tracer, wheat germ agglutinated-horseradish peroxidase were placed in the substantia nigra, in adjoining dopamine-containing cell groups A8 and A10, and in the internal and external parts of the pallidal complex of 20 cats in order to identify the compartmental origins of striatal efferent projections to the pallidum and midbrain. Patterns of retrograde cell-labeling in the caudate nucleus were analysed with respect to its striosomal architecture as detected in sections stained for acetylcholinesterase. Where possible, a similar compartmental analysis of cell-labeling in the putamen was also carried out. In 15 cats anterograde labeling in the striatum was studied in the sections stained with wheat germ agglutinated-horseradish peroxidase or in autoradiographically treated sections from cases in which [35S]methionine was mixed with the wheat germ agglutinated-horseradish peroxidase in the injection solution. Predominant labeling of projection neurons lying in striosomes (usually with some labeling of dorsomedial matrix neurons) occurred in a subset of the cases of nigral injection, including all cases (n = 9) in which the injection sites were centered in the densocellular zone of the substantia nigra pars compacta [Jiménez-Castellanos J. and Graybiel A. M. (1987) Neuroscience 23, 223-242.] Dense labeling of neurons in the extrastriosomal matrix, with at most sparse labeling of striosomal neurons, occurred in all cases of pallidal injection (n = 8) and in two cases of nigral injection in which the injection sites were lateral and anterior to the densocellular zone. Mixed labeling of striosomal and matrical neurons occurred in a third group of cases in which the injection sites were lateral to the densocellular zone but close to it. In a single case with an injection site situated in the pars lateralis of the substantia nigra, there was preferential labeling of striosomal neurons in the caudal caudate nucleus but widespread labeling of neurons in both striosomes and matrix in the putamen. A second type of compartmental ordering of projection neurons was found in the extrastriosomal matrix of the striatum. In cases of pallidal and nigral injection, there were gaps in cell labeling that did not match striosomes precisely, and often clusters of labeled cells appeared that did not correspond to acetylcholinesterase-poor striosomes but, instead, to patches of matrix. Especially prominent were clusters beside striosomes. There was a topographic ordering of striatal projection neurons both in the striosomes and in the extrastriosomal matrix according to their dorsoventral and latitudinal positions.(ABSTRACT TRUNCATED AT 400 WORDS)

Dopamine D1 binding sites in the striatum of the mutant mouse weaver

In the weaver mouse there is a major abnormality in the dopamine-containing innervation of the striatum. Dopamine islands from during development, along with some innervation of the non-islandic matrix; but during the first postnatal month much of the islandic innervation degenerates and there is a failure of the normal postnatal development of the diffuse nigrostriatal innervation. In the experiments reported here we analysed the distribution of D1 dopamine receptor-related binding sites in the weaver striatum in an effort to test the relationship between the dopamine-containing innervation of the striatum and the synthesis and distribution of dopamine receptors there. Dopamine D1 receptor binding sites labeled by the D1 specific antagonist [3H]SCH 23390 were studied in the striatum of 7-day and adult homozygous weaver (wv/wv) and homozygous control (+/+) mice. Saturation analysis of [3H]SCH 23390 binding in adult animals suggested that the dissociation constants of the binding sites are similar in mutants and controls. The Bmax values in the striatum of weavers were 16% higher than in the controls when the data were expressed as fmoles/mg protein. The protein content of the adult weaver's striatum was decreased by 15 to 30%, however, so that when values were expressed as fmoles/section, no significant difference between values in weavers and homozygous controls were found. Quantitative autoradiography supported the results of saturation analysis. We conclude that the apparent increase of [3H]SCH23390 binding sites in the mutants occurred as the result of shrinkage of the weaver's caudoputamen and that dopamine D1 receptor binding sites in the caudoputamen, as assessed with [3H]SCH 23390, are normal. The studies of regional distribution of [3H]SCH 23390 binding sites in 7-day and adult mice indicated that the characteristic postnatal transition of the [3H]SCH 23390 binding pattern from islandic to a diffuse distribution occurred normally in the weaver's caudoputamen. Thus, in spite of the degeneration and failure of development of the nigrostriatal innervation in weaver mice, D1 binding in the weaver's striatum undergoes the elaborate change in distribution of these sites that is a hallmark of normal striatal development.