Patterns of tachykinin expression and localization in developing feline neostriatum

The non-human primate striatum undergoes marked prolonged remodeling during postnatal development

We examined the postnatal ontogeny of the striatum in rhesus monkeys (Macaca mulatta) to identify temporal and spatial patterns of histological and chemical maturation. Our goal was to determine whether this forebrain structure is developmentally static or dynamic in postnatal life. Brains from monkeys at 1 day, 1, 4, 6, 9, and 12 months of age (N = 12) and adult monkeys (N = 4) were analyzed. Nissl staining was used to assess striatal volume, cytoarchitecture, and apoptosis. Immunohistochemistry was used to localize and measure substance P (SP), leucine-enkephalin (LENK), tyrosine hydroxylase (TH), and calbindin D28 (CAL) immunoreactivities. Mature brain to body weight ratio was achieved at 4 months of age, and striatal volume increased from ∼1.2 to ∼1.4 cm(3) during the first postnatal year. Nissl staining identified, prominently in the caudate nucleus, developmentally persistent discrete cell islands with neuronal densities greater than the surrounding striatal parenchyma (matrix). Losses in neuronal density were observed in island and matrix regions during maturation, and differential developmental programmed cell death was observed in islands and matrix regions. Immunohistochemistry revealed striking changes occurring postnatally in striatal chemical neuroanatomy. At birth, the immature dopaminergic nigrostriatal innervation was characterized by islands enriched in TH-immunoreactive puncta (putative terminals) in the neuropil; TH-enriched islands aligned completely with areas enriched in SP immunoreactivity but low in LENK immunoreactivity. These areas enriched in SP immunoreactivity but low in LENK immunoreactivity were identified as striosome and matrix areas, respectively, because CAL immunoreactivity clearly delineated these territories. SP, LENK, and CAL immunoreactivities appeared as positive neuronal cell bodies, processes, and puncta. The matrix compartment at birth contained relatively low TH-immunoreactive processes and few SP-positive neurons but was densely populated with LENK-immunoreactive neurons. The nucleus accumbens part of the ventral striatum also showed prominent differences in SP, LENK, and CAL immunoreactivities in shell and core territories. During 12 months of postnatal maturation salient changes occurred in neurotransmitter marker localization: TH-positive afferents densely innervated the matrix to exceed levels of immunoreactivity in the striosomes; SP immunoreactivity levels increased in the matrix; and LENK-immunoreactivity levels decreased in the matrix and increased in the striosomes. At 12 months of age, striatal chemoarchitecture was similar qualitatively to adult patterns, but quantitatively different in LENK and SP in caudate, putamen, and nucleus accumbens. This study shows for the first time that the rhesus monkey striatum requires more than 12 months after birth to develop an adult-like pattern of chemical neuroanatomy and that principal neurons within striosomes and matrix have different developmental programs for neuropeptide expression. We conclude that postnatal maturation of the striatal mosaic in primates is not static but, rather, is a protracted and dynamic process that requires many synchronous and compartment-selective changes in afferent innervation and in the expression of genes that regulate neuronal phenotypes.

Tachykinin-immunoreactive neurons in developing feline neostriatum: somatodendritic morphogenesis demonstrated by combined immunohistochemistry/Golgi impregnation-gold toning

This investigation was designed to survey and characterize the development of a key link between chemically mediated neurotransmission and neuronal cytoarchitecture in mammalian basal ganglia. Peroxidase immunohistochemical and Golgi impregnation/gold toning methods were combined to doubly label the tachykinin neuromodulator signature and somatodendritic structure of neostriatal neurons in late fetal, postnatal and adult cats. The results supported 3 conclusions of considerable significance. (1) Colocalization of immunohistochemical and Golgi impregnation/gold toning labels is a feasible, rational and productive means to identify and determine the somatodendritic morphogenesis of tachykinin neurons. (2) The application of this method to developing feline neostriatum demonstrates directly that the principal tachykinin cells are medium-sized spiny neurons, which undergo progressive growth and elaboration of cell bodies, dendritic arbors and dendritic spines during the late fetal and postnatal periods. (3) There is a strong but incomplete concordance between tachykinin and medium-sized spiny neuronal phenotypes, because a minor variant of medium-sized spiny neurons and rare subgroups of medium- and large-sized sparse spiny neurons also show the tachykinin neuromodulator signature. Taken together, these results suggest that neostriatal neurons show an early commitment to heterogeneous tachykinin phenotypes, although the full and final expression of their somatodendritic characteristics coincides with synaptogenesis.

Postnatal development of the dopaminergic neurons in the rat mesencephalon

The two mesencephalic dopaminergic systems in the developing rat brain were investigated immunohistochemically by dopamine and tyrosine hydroxylase and the results were quantitatively analyzed with a computer. The number of the dopaminergic neurons in the substantia nigra and the ventral tegmentum area did not change significantly during the postnatal development. Dopaminergic terminals in the lateral septum peaked at postnatal days (PD) 30, when the cell size in middle third of the ventral tegmentum area which was suggested as an origin of this projection system, increased largely. Patchy structures in the striatum were shown most distinctly at PD 7 and disappeared at PD 35 using dopamine antibody, but there were no changes in the cell size of the substantia nigra from PD 14 to 75. Dopaminergic neurons, in general, do not show a transient change in ontogeny.

Fos-like immunoreactivity in tyrosine hydroxylase and substance P-like immunoreactive neurones in guinea-pig brain following intracerebroventricular injection of morphine and U50,488H

Opioid drugs such as morphine have powerful reinforcing effects which lead to drug-seeking behaviour. Both dopamine- and substance P-containing neurones have been implicated in reward. In the present study twocolour immunohistochemistry was used to investigate whether Fos protein was induced in dopaminergic (tyrosine hydroxylase) and substance P-containing neurones of guinea-pig brain following intracerebroventricular administration of the predominantly mu-receptor agonist, morphine, and the kappa-receptor agonist, U50,488H, which have been reported to produce rewarding and aversive effects, respectively. The present study has shown that of the large number of neurones showing Fos-like immunoreactivity following a single injection of morphine or U50,488H, few were tyrosine hydroxylase-positive (dopaminergic) but a larger number were substance Plike immunoreactive. These results support the proposal that substance P plays a role in reward and reinforcement.

The development of striatal patch/matrix organization after prenatal methylazoxymethanol: a combined immunocytochemical and bromo-deoxy-uridine birthdating study

The antimitotic drug methylazoxymethanol was used to destroy striatal patch neurons during their three-day-period of neurogenesis in the rat. Single or multiple injections of methylazoxymethanol were given during embryonic days 13-15, the period when patch neurons are known to undergo their final cell division. Methylazoxymethanol treatments produced a dramatic reduction in striatal volume. Immunocytochemical analysis revealed the continued presence of patches of neurons that were substance P-immunoreactive and devoid of calbindin and enkephalin immunoreactivity. Both the number of patches and relative volume occupied by patches was reduced in methylazoxymethanol-treated striata. Patch neurons could also be labelled by an intrastriatal injection of FluoroGold during the first postnatal week. The early ingrowth of nigrostriatal dopamine afferents was less noticeably patchy in the methylazoxymethanol-treated animals, in part owing to an overall increase in density. Large reductions in the number of neurons immunoreactive for choline acetyltransferase were observed, whereas NADPH diaphorase-stained neurons were not reduced unless methylazoxymethanol was given on embryonic day 15. Injections of bromo-deoxy-uridine, either during or after the 24 h that each methylazoxymethanol injection was considered to be effective, revealed that (i) some patch neurons continued to be generated in the 24-h period following methylazoxymethanol administration, and (ii) many patch neurons were generated after the effects of methylazoxymethanol had worn off. These findings demonstrate that it was impossible to completely eliminate the patches using methylazoxymethanol injections during the period of patch neurogenesis. However, methylazoxymethanol treatment during this time did produce a dramatic loss of cells and a relatively greater reduction in patch volume. Despite this disruption, the appropriate compartmentalization of neuroactive substances appeared to be maintained.

The development of enkephalin and substance P neurons in the basal ganglia: insights into neostriatal compartments and the extended amygdala

To study the comparative development of the two major neuropeptide genes of the striatum, we used immunocytochemistry to detect immunoreactivity (ir) for substance P and synenkephalin (the N terminus of proenkephalin), and in situ hybridization to detect proenkephalin mRNA. Earliest detection of substance P-ir was in the anlage of the bed nucleus of the stria terminalis (BST, at E15) and in the rostral-lateral caudate-putamen (CPu), at E16. Substance P in the BST was immediately subjacent to the medial ganglionic eminence, while immunoreactivity in the CPu was associated with the lateral ganglionic eminence. Earliest detection of synenkephalin-ir or proenkephalin mRNA was in the caudal-lateral CPu and the adjacent central nucleus of the amygdala (Ce), at E16. Over the next several days, expression of each neuropeptide spread toward the region of first expression of the other neuropeptide. The first overlap of expression of the two neuropeptides was at E18, at the level of the septum. Despite correspondence of substance P-ir and proenkephalin mRNA in patches at P0, very little co-expression of the two neuropeptides was evident in individual neurons. We propose a model in which the CPu develops primarily from the lateral ganglionic eminence, and the extended amygdala develops primarily from the medial ganglionic eminence. Within each structure, two poles of neuropeptide gene expression are established initially: substance P-ir in the rostral CPu and in the rostral-medial pole of the extended amygdala (represented by the BST), and synenkephalin/proenkephalin in the caudal CPu and in the caudal-lateral pole of the extended amygdala (represented by the Ce). A stream of substance P-ir cells connects the two poles of the extended amygdala, in the sublenticular substantia innominata.

Cholinergic neurons are distributed preferentially in areas rich in substance P-like immunoreactivity in the caudate nucleus of the adult cat

The distribution of cells stained immunocytochemically for the cholinergic marker choline acetyltransferase was compared to the pattern of substance P immunoreactivity in the caudate nucleus of adult cats using a double-label immunocytochemical protocol and three-dimensional reconstructions of adjacent sections single-labeled for either substance P or choline acetyltransferase. Substance P immunoreactivity was distributed in a highly complex mosaic within the caudate nucleus of the cat. In the dorsal caudate nucleus, substance P-rich zones consisting of either clusters of substance P-positive cell bodies or fibers were seen against a lighter staining background. The density of cholinergic neurons was found to be significantly greater within these substance P-rich patches in comparison to surrounding regions. The pattern of substance P immunoreactivity within the ventral caudate nucleus differed from that in more dorsal regions. Clear substance P-rich patches were not seen in this region, but a large substance P-rich area consisting of a dense plexus of substance P-containing fibers was visible. Embedded within this substance P-rich area were fairly discrete patches of light substance P staining. As in the dorsal caudate nucleus, increased numbers of cholinergic neurons and processes were associated with substance P-rich regions in the ventral caudate nucleus. Choline acetyltransferase-positive perikarya also appeared to be concentrated in substance P-rich areas in the nucleus accumbens and olfactory tubercle. The results of this study suggest that a close relationship exists between the distribution of substance P fibers and cholinergic perikarya in the striatum of the cat.

Species-specific patterns of glycoprotein expression in the developing rodent caudoputamen: association of 5'-nucleotidase activity with dopamine islands and striosomes in rat, but with extrastriosomal matrix in mouse

The glycoprotein 5'-nucleotidase is a cell surface phosphatase and represents a new marker for striosomes in the adult rat caudoputamen. We report here on its developmental expression in the rat and mouse striatum, and show an unexpected converse 5'-nucleotidase chemoarchitecture of the caudoputamen in these closely related species. In the rat, 5'-nucleotidase activity was first visible as neuropil staining in tyrosine hydroxylase-positive dopamine islands of the midstriatum on postnatal day 1, and by the end of the first postnatal week, 5'-nucleotidase-positive dopamine islands also appeared rostrally. This compartmental pattern persisted thereafter, so that in adult animals, in all but the caudal caudoputamen, zones of enhanced 5'-nucleotidase staining were restricted to calbindin-D28k-poor striosomes. Weak 5'-nucleotidase activity also emerged in the matrix. In striking contrast, in the mouse striatum, enhanced 5'-nucleotidase activity was preferentially associated with extrastriosomal tissue. Enzymatic reaction first appeared on embryonic day 18, and developed over the first postnatal week into a mosaic pattern in which the matrix was stained but the dopamine islands were unstained. The matrix staining itself was heterogeneous. After the second postnatal week, most of the caudoputamen was stained, and in adult mice only rostral striosomes expressed low 5'-nucleotidase activity. We conclude that in rats, 5'-nucleotidase represents one of the few substances that maintains a preferential dopamine island/striosome distribution during striatal development. In mice, 5'-nucleotidase activity is expressed preferentially in the matrix during development, and its compartmental pattern is gradually lost with maturation, except very rostrally. These findings do not suggest an instructive role of the enzyme in striatal compartment formation in either species, but do suggest the possibility that 5'-nucleotidase contributes to the differentiation of striatal compartments during development.

Comparative distribution of neurokinin B-, substance P- and enkephalin-like immunoreactivities and neurokinin B messenger RNA in the basal forebrain of the rat: evidence for neurochemical compartmentation

The distribution of neurokinin B was investigated in the basal forebrain of the rat by immunocytochemistry with an antibody directed against neurokinin B, and with a second antiserum directed to a peptide sequence contained within its precursor, and by means of in situ hybridization. The staining pattern was compared in closely adjacent sections to that of substance P- and enkephalin-like immunoreactivities. Cholecystokinin immunoreactivity was used to delineate the apparent dorsolateral border of the ventral pallidum with the nucleus accumbens. Remarkable similarities are found in the distribution of these peptides in the basal forebrain, especially in its ventral part. The coarse band-like terminal staining pattern (woolly fibers) that has been shown by others for substance P- and enkephalin-like immunoreactivity, is also observed for neurokinin B-like immunoreactivity, mainly in the ventral pallidum. Medium-sized cells are found arranged in clusters or singularly within the caudate-putamen even without colchicine. A band of strong neurokinin B immunoreactivity extends just underneath the dorsal pallidum to the amygdala. In comparison to enkephalin the most distinct observation is that neurokinin B immunoreactivity is not present in the dorsal pallidum (global pallidus). Neurokinin B immunoreactivity was not found in the pars reticulata of the substantia nigra which is strongly immunopositive for substance P. The number of cells detected by in situ hybridization was higher compared to the immunopositive perikarya throughout the basal ganglia. The staining pattern observed reflects a partial overlap with the substance P and enkephalin system although a differential distribution for each of these peptides was observed for cell bodies and axons terminals.

Heterogeneous development of calbindin-D28K expression in the striatal matrix

In the present study, we attempted to trace the development of the striatal matrix by analyzing the ontogenetic expression of calbindin-D28K (calbindin), a calcium binding protein selectivity expressed in medium-sized neurons of the matrix compartment of the mature rat's caudoputamen. The localization of calbindin was documented in a series of developing rat brains, as was the compartmental location of these cells relative to tyrosine hydroxylase (TH)-immunostained dopamine islands, sites of future striosomes. Medium-sized striatal neurons appeared in the striatum at embryonic day (E) 20, and from their first appearance, the calbindin-positive neurons had highly heterogeneous distributions. They first formed a latticework of patches and bands in a ventral region of the caudoputamen. By postnatal day (P) 7, this early calbindin-positive lattice had evolved into a mosaic in which circumscript pockets of low calbindin-like immunoreactivity appeared in more extensive calbindin-rich surrounds. With further development, the mosaic gradually encroached on all but the dorsolateral caudoputamen, a district that is calbindin-poor at adulthood. A special lateral branch of the striatal calbindin system was also identified, distinct from the rest of the calbindin-positive mosaic in several developmental characteristics. In the parts of the caudoputamen where the developing calbindin system and dopamine island system were both present, the dopamine islands invariably lay in calbindin-poor zones. Most dopamine islands, however, only filled parts of the corresponding calbindin-poor zones. Moreover, there were some calbindin-poor zones for which TH-positive dopamine islands could not be detected. Thus during development, calbindin was expressed in the extrastriosomal matrix of the striatum, but the matrix could be divided into calbindin-rich and calbindin-poor zones. In the calbindin-rich regions, there were patches of especially intense calbindin expression and zones of weaker expression. These results suggest that there is neurochemical heterogeneity in the striatal matrix during the prolonged developmental period in which the early calbindin-positive lattice expands to form the calbindin-positive matrix of the mature striatum. Surprisingly, calbindin expression in the matrix, although eventually distributed in strictly complementary fashion to striosomes, does not originate as a system complementary to dopamine islands. The prolonged disparity between the borders of dopamine islands and calbindin-poor zones, and the different spatiotemporal schedules of development of the islands and the calbindin gaps suggest instead that the final match between the borders of striosomes and surrounding matrix results from dynamic processes occurring early in postnatal development. Candidate mechanisms for the gradual adjustment of these borders are proposed.

Ontogeny of gene expression of adenosine A2 receptor in the striatum: early localization in the patch compartment

The ontogeny of adenosine A2 receptor mRNA and adenosine A2 binding sites distributions was studied by in situ hybridization histochemistry and receptor autoradiography in pre- and post-natal rat striatum, postnatal dog striatum, and a human fetus striatum and compared to that of dopamine D1 and mu opiate receptors. The early postnatal striatum demonstrated heterogeneous distributions of adenosine A2 receptor mRNA and adenosine A2 binding sites with patches of dense labeling corresponding to dopamine D1 and mu opiate receptors enriched zones. This patchy pattern evolved to the homogeneous distribution observed in the adult. The higher intensity of adenosine A2 receptor mRNA enriched patches correspond at the microscopical level to a higher density of labeled neurons in the patches areas and also to a higher level of expression per labeled patches neuron than in the matrix ones. This demonstrates for the first time that differences in patch/matrix receptor density is at least partly linked to different levels of receptor gene expression.