The comparison between enkephalin-like and dynorphin-like immunoreactivity in both monkey and human globus pallidus and substantia nigra

Distribution of ubiquilin 2 and TDP-43 aggregates throughout the CNS in UBQLN2 p.T487I-linked amyotrophic lateral sclerosis and frontotemporal dementia

Mutations in the UBQLN2 gene cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The neuropathology of such UBQLN2-linked cases of ALS/FTD is characterised by aggregates of the ubiquilin 2 protein in addition to aggregates of the transactive response DNA-binding protein of 43 kDa (TDP-43). ALS and FTD without UBQLN2 mutations are also characterised by TDP-43 aggregates, that may or may not colocalise with wildtype ubiquilin 2. Despite this, the relative contributions of TDP-43 and ubiquilin 2 to disease pathogenesis remain largely under-characterised, as does their relative deposition as aggregates across the central nervous system (CNS). Here we conducted multiplex immunohistochemistry of three UBQLN2 p.T487I-linked ALS/FTD cases, three non-UBQLN2-linked (sporadic) ALS cases, and 8 non-neurodegenerative disease controls, covering 40 CNS regions. We then quantified ubiquilin 2 aggregates, TDP-43 aggregates and aggregates containing both proteins in regions of interest to determine how UBQLN2-linked and non-UBQLN2-linked proteinopathy differ. We find that ubiquilin 2 aggregates that are negative for TDP-43 are predominantly small and punctate and are abundant in the hippocampal formation, spinal cord, all tested regions of neocortex, medulla and substantia nigra in UBQLN2-linked ALS/FTD but not sporadic ALS. Curiously, the striatum harboured small punctate ubiquilin 2 aggregates in all cases examined, while large diffuse striatal ubiquilin 2 aggregates were specific to UBQLN2-linked ALS/FTD. Overall, ubiquilin 2 is mainly deposited in clinically unaffected regions throughout the CNS such that symptomology in UBQLN2-linked cases maps best to the aggregation of TDP-43.

Three divisions of the mouse caudal striatum differ in the proportions of dopamine D1 and D2 receptor-expressing cells, distribution of dopaminergic axons, and composition of cholinergic and GABAergic interneurons

The greater part of the striatum is composed of striosomes and matrix compartments, but we recently demonstrated the presence of a region that has a distinct structural organization in the ventral half of the mouse caudal striatum (Miyamoto et al. in Brain Struct Funct 223:4275-4291, 2018). This region, termed the tri-laminar part based upon its differential immunoreactivities for substance P and enkephalin, consists of medial, intermediate, and lateral divisions. In this study, we quantitatively analyzed the distributions of both projection neurons and interneurons in each division using immunohistochemistry. Two types of projection neurons expressing either the dopamine D1 receptor (D1R) or D2 receptor (D2R) showed complementary distributions throughout the tri-laminar part, but the proportions significantly differed among the three divisions. The proportion of D1R-expressing neurons in the medial, intermediate, and lateral divisions was 88.6 ± 8.2% (651 cells from 3 mice), 14.7 ± 3.8% (1025 cells), and 49.3 ± 4.5% (873 cells), respectively. The intermediate division was further characterized by poor innervation of tyrosine hydroxylase immunoreactive axons. The numerical density of choline acetyltransferase immunoreactive neurons differed among the three divisions following the order from the medial to lateral divisions. In contrast, PV-positive somata were distributed throughout all three divisions at a constant density. Two types of GABAergic interneurons labeled for nitric oxide synthase and calretinin showed the highest cell density in the medial division. The present results characterize the three divisions of the mouse caudal striatum as distinct structures, which will facilitate studies of novel functional loops in the basal ganglia.

An anxiolytic role for CRF receptor type 1 in the globus pallidus

Corticotropin-releasing factor receptor type 1 (CRFR1) plays a major role in the regulation of neuroendocrine and behavioral responses to stress and is considered a key mediator of anxiety behavior. The globus pallidus external (GPe), a main relay center within the basal ganglia that is primarily associated with motor and associative functions, is one of the brain nuclei with the highest levels of CRFR1 expression in the rodent brain. However, the role of CRFR1 in the GPe is yet unknown. In the present study, we used a lentiviral-based system of RNA interference to show that knockdown of CRFR1 mRNA expression in the GPe of adult mice induces a significant increase in anxiety-like behavior, as revealed by the light-dark transfer, open-field, and elevated plus-maze tests. This effect was further confirmed by pharmacological administration of the selective CRFR1 antagonist NBI 30775 (1.75 μg/side) directly into the GPe. In the marble-burying test, blockade of CRFR1 in the GPe increased the percentage of marbles buried and the duration of burying behavior. Additionally, we present evidence suggesting that the enkephalin system is involved in the effect of GPe-CRFR1 on anxiety-like behavior. In contrast to the well established anxiogenic role of CRFR1 in the extended amygdala, our data reveal a novel anxiolytic role for CRFR1 in the GPe.

Topographic organization of the ventral striatal efferent projections in the rhesus monkey: an anterograde tracing study

The ventral striatum is considered to be that portion of the striatum associated with the limbic system by virtue of its afferent connections from allocortical and mesolimbic areas as well as from the amygdala. The efferent projections from this striatal region in the primate were traced by using 3H amino acids and Phaseolus vulgaris-leucoagglutinin (PHA-L). Particular attention was paid to the topographic organization of terminal fields in the globus pallidus and substantia nigra, the projections to non-extrapyramidal areas, the relationship between projections from the nucleus accumbens and the other parts of the ventral striatum, and the comparison between ventral and dorsal striatal projections. This study demonstrates that in monkeys a circumscribed region of the globus pallidus receives topographically organized efferent fibers from the ventral striatum. The ventral striatal fibers terminate in the ventral pallidum, the subcommissural part of the globus pallidus, the rostral pole of the external segment, and the rostromedial portion of the internal segment. The more central and caudal portions of the globus pallidus do not receive this input. This striatal output appears to remain segregated from the dorsal striatal efferent projections to pallidal structures. Fibers from the ventral striatum projecting to the substantia nigra are not as confined to a specific region as those projecting to the globus pallidus. Although the densest terminal fields occur in the medial portion, numerous fibers also extend laterally to innervate the dorsal stratum of dopaminergic neurons of the substantia nigra and the retrorubral area. Furthermore, they project throughout the rostral-caudal extent of the substantia nigra. Projections from the medial part of the ventral striatum reach the more caudally located pedunculopontine tegmental nucleus. Thus unlike the above described terminals in the globus pallidus, the ventral striatum project widely throughout the substantia nigra, a fact that indicates that they may contribute to the integration between limbic and other output systems of the striatum. Finally, the ventral striatum projects to non-extrapyramidal regions including the bed nucleus of the stria terminals, the nucleus basalis magnocellularis, the lateral hypothalamus, and the medial thalamus.

Differential messenger RNA expression of prodynorphin and proenkephalin in the human brain

The opiate system is involved in a wide variety of neural functions including pain perception, neuroendocrine regulation, memory, drug reward, and tolerance. Such functions imply that endogenous opioid peptides should have anatomical interactions with limbic brain structures believed to be involved in the experience and expression of emotion. Using in situ hybridization histochemistry, the messenger RNA expression of the opioid precursors, prodynorphin and proenkephalin, was studied in whole hemisphere human brain tissue. Different components of the limbic system were found to be characterized by a high gene expression of either prodynorphin or proenkephalin messenger RNA. Brain regions traditionally included within the limbic system (e.g. amygdala, hippocampus, entorhinal cortex and cingulate cortex) as well as limbic-associated regions including the ventromedial prefrontal cortex and patch compartment of the neostriatum showed high prodynorphin messenger RNA expression. In contrast, high levels of proenkephalin messenger RNA were more widely expressed in the hypothalamus, periaqueductal gray, various mesencephalic nuclei, bed nucleus of the stria terminalis, and ventral pallidum; brain regions associated with endocrine-reticular-motor continuum of the limbic system. The marked anatomical dissociation between the expression of these two opioid peptide genes, seen clearly in whole hemisphere sections, indicates that distinct functions must be subserved by the prodynorphin and proenkephalin systems in the human brain.

Ontogeny of the striatal neurons expressing neuropeptide genes in the human fetus and neonate

The distribution patterns of neurons expressing mRNAs for four neuropeptides in the human striatum were studied during ontogeny by the use of in situ hybridization. The results of our study demonstrate that somatostatin, enkephalin, dynorphin, and substance P mRNAs are present in striatal neuronal populations from week 12 of fetal life. Each neuronal population undergoes a specific differentiation. Neurons containing somatostatin mRNA are scattered throughout the caudate-putamen up until birth. Neurons containing enkephalin, dynorphin, or substance P mRNAs evolve throughout fetal life in relation to caudate-putamen and patch-matrix compartmentalization. Neurons containing enkephalin mRNA (distinct from those containing substance P or dynorphin mRNAs) are present in the matrix from week 12 of fetal life. These neurons are preferentially distributed in the matrix and, at birth, display higher enkephalin mRNA content in the matrix than in the patches. Dynorphin mRNA is found in the caudate and putamen, preferentially in the patch neurons; nevertheless, a low level of dynorphin mRNA is also present in neurons of the caudate matrix. Substance P mRNA is initially restricted to caudate neurons. At birth, both substance P and dynorphin mRNAs are expressed at high levels in the patches. These results demonstrate that each neuropeptide gene is expressed during human fetal life in neurons with a specific topology and pace of development in relation to caudate-putamen and patch-matrix differentiation. These results also contribute evidence that neurochemical evolution of the striatal neuronal populations is not complete at birth in humans.

The human neostriatum shows compartmentalization of neuropeptide gene expression in dorsal and ventral regions: an in situ hybridization histochemical analysis

Expression of neuropeptide messenger RNAs in striatal neurons was studied in post mortem human brain tissue by the use of in situ hybridization histochemistry. Clusters of cells expressing high levels of prodynorphin messenger RNA, and less strikingly, preprotachykinin messenger RNA, were prominent in the caudate nucleus and were present but less pronounced in the putamen. Proenkephalin and prosomatostatin messenger RNA-containing cells were more homogeneously distributed throughout the striatum, though the latter were much sparser. The four neuropeptide messenger RNA patterns in the nucleus accumbens were rather homogeneous compared with the dorsal striatum. Of these, prodynorphin messenger RNA showed a higher level of expression per cell in the nucleus accumbens relative to the dorsal striatum. The relationship of neuropeptide-containing cell clusters to the striosomal organization was characterized by looking at the register of these markers with patterns of low acetylcholinesterase activity and dense mu opiate receptor binding. In the caudate and putamen, clusters of cells expressing high levels of dynorphin and preprotachykinin messenger RNAs were clearly in register with the striosomes. The accumbens was defined by high prodynorphin messenger RNA levels, both low and high levels of acetylcholinesterase staining, and very low to absent mu opiate receptor binding. The distribution of high-expressing prodynorphin messenger RNA-containing cells--to the patch compartment and throughout the entire ventral striatum/nucleus accumbens region--defines the limbic domain of the neostriatum and suggests particular relevance to human striatal organization and function, because the distribution of this opioid neuropeptide is considerably more compartmentalized in human than in non-human species.

Dendritic domains of medium spiny neurons in the primate striatum: relationships to striosomal borders

Medium spiny neurons are the projection neurons of the striatum. They receive the majority of striatal afferents, and they make up the vast majority of all neurons in the striatum. These densely spiny cells thus constitute a major substrate for input-output processing in the striatum. In the experiments described here we analyzed the dendritic fields of spiny neurons in the squirrel monkey striatum and plotted their orientations with respect to the borders between striosomes and matrix. Medium-sized spiny neurons in the caudate nucleus were filled intracellularly in a fixed-slice preparation with the fluorescent dye Lucifer Yellow. Dendritic arbors were reconstructed following immunostaining of the injected neurons with antiserum to Lucifer Yellow and counterstaining for striosome/matrix compartments. A majority of the medium spiny neurons studied had dendritic arborizations that remained within their compartment of origin. Thus the striosome/matrix subdivision not only partitions neurotransmitter molecules and extrinsic striatal connections into two domains in the primate caudate nucleus, but also constrains the dendritic arbors of many projection neurons there. Other medium spiny neurons, however, in both striosomes and matrix, had dendrites that crossed from one compartment into the other. About a quarter of the spiny neurons reconstructed had at least one such crossing dendrite. These results suggest that compartmentalization of afferent and efferent processing by projection neurons in the primate striatum is not absolute. For a subpopulation of spiny neurons in striosomes and matrix, inputs to one compartment could have a direct influence on output cells of the other.

Rapid induction of heme oxygenase 1 mRNA and protein by hyperthermia in rat brain: heme oxygenase 2 is not a heat shock protein

Catalytic activity of heme oxygenase (heme, hydrogen-donor:oxygen oxidoreductase, EC 1.14.99.3) isozymes, HO-1 and HO-2, permits production of physiologic isomers of bile pigments. In turn, bile pigments biliverdin and bilirubin are effective antioxidants in biological systems. In the rat brain we have identified only the HO-1 isozyme of heme oxygenase as a heat shock protein and defined hyperthermia as a stimulus that causes an increase in brain HO-1 protein. Exposure of male rats to 42 degrees C for 20 min caused a rapid and marked increase in brain 1.8-kilobase HO-1 mRNA. Specifically, a 33-fold increase in brain HO-1 mRNA was observed within 1 h and sustained for at least 6 h posttreatment. In contrast, the two HO-2 homologous transcripts (1.3 and 1.9 kilobases) did not respond to heat shock; neither the ratio nor the level of the two messages differed from that of the control when measured either at 1, 6, or 24 h after hyperthermia. The induction of a 1.8-kilobase HO-1 mRNA resulted in a pronounced increase in HO-1 protein 6 h after hyperthermia, as detected by both Western immunoblot and RIA. Immunocytochemistry of rat brain showed discrete localization of HO-1-like protein only in neurons of select brain regions. Six hours after heat shock, an intense increase in HO-1-like protein was observed in both Purkinje cells of the cerebellum and epithelial cells lining the cerebral aqueduct of the brain. We suggest that the increase in HO-1 protein, hence increased capacity to form bile pigments, represents a neuronal defense mechanism against heat shock stress.

Autoradiographic localization of delta opiate receptors in rat and human brain

In vitro quantitative receptor autoradiography was performed on frozen sections of rat and human brain to visualize delta opiate receptors using the specific ligand [3H][D-Pen2, D-Pen5]enkephalin. For comparison, rat brain sections were also labelled with [3H]D-Ala2, D-Leu5-enkephalin. Compounds which block mu and kappa binding were included to make the [3H]D-Ala2, D-Leu5-enkephalin binding more specific. The two ligands had similar, but not identical, distributions in rat forebrain sections. Sites labelled with [3H][D-Pen2,D-Pen5]enkephalin were distributed heterogeneously within the layers of the frontal and parietal cerebral cortex, with high densities in the superficial and deep cortical layers. The claustrum and striatum had the most delta sites, whereas the globus pallidus had no delta binding. The distribution of [3H]D-Ala2,D-Leu5-enkephalin binding sites was similar to that of [3H][D-Pen2,D-Pen5]enkephalin, except that there was less heterogeneity in the frontal cortex. In the human brain regions studied, the highest delta binding was in caudate, putamen, temporal cortex and amygdala. There was less heterogeneity in the binding of [D-Pen2,D-Pen5]enkephalin in the human cortex than in the rat. No delta binding was seen in the medial and lateral segments of the globus pallidus. In both species, a discrepancy between the high enkephalin content of the globus pallidus and the absence of delta binding was apparent.

Characterization of substance P- and [Met]enkephalin-immunoreactive neurons in the caudate nucleus of cat and ferret by a single section Golgi procedure

Modifications of the single-section Golgi-impregnation procedure of Gabbott and Somogyi are described. The modifications allow easier and more rapid preparation of the sections for Golgi-impregnation and easier handling of large numbers of serial sections. The technique consists of placing a section that has been treated with osmium tetroxide and potassium dichromate on a microscope slide and "sandwiching" it with a second microscope slide. The two slides are held together at one end by tape and the assembly is dipped into a solution of silver nitrate. Golgi-impregnation of neurons occurs within a few hours and is generally complete within 12 h. The technique has been applied to sections through the caudate nucleus of the cat and ferret in order to define the morphological characteristics of striatal substance P- and methionine enkephalin-immunoreactive neurons. Sections were first incubated to reveal the immunoreactive structures and then subjected to the Golgi method. Golgi-impregnated neurons that were immunoreactive for either substance P or methionine enkephalin had medium-size perikarya from which several dendrites emerged. The dendrites branched close to the perikaryon; secondary and higher order dendrites were densely laden with spines, as many as 15 spines per 10 microns of dendrite. It is concluded that both striatal substance P-containing and methionine enkephalin-containing neurons are of the medium-size densely spiny type. Medium-size densely spiny neurons may be homogeneous with respect to their somatodendritic morphology but heterogeneous with respect to their chemical characteristics and axonal morphology.

Distribution of dynorphin and enkephalin peptides in the rat brain

The neuroanatomical distribution of dynorphin B-like immunoreactivity (DYN-B) was studied in the adult male and female albino rat. The distribution of DYN B in colchicine- and noncolchicine-treated animals was also compared to that of another opioid peptide derived from the prodynorphin precursor dynorphin A (1-8) (DYN 1-8), and an opioid peptide derived from the proenkephalin precursor met-enkephalin-arg-gly-leu (MERGL). DYN B cell bodies were present in nonpyramidal cells of neo- and allocortices, medium-sized cells of the caudate-putamen, nucleus accumbens, lateral part of the central nucleus of the amygdala, bed nucleus of the stria terminalis, preoptic area, and in sectors of nearly every hypothalamic nucleus and area, medial pretectal area, and nucleus of the optic tract, periaqueductal gray, raphe nuclei, cuneiform nucleus, sagulum, retrorubral nucleus, peripeduncular nucleus, lateral terminal nucleus, pedunculopontine nucleus, mesencephalic trigeminal nucleus, parabigeminal nucleus, dorsal nucleus of the lateral lemniscus, lateral superior olivary nucleus, superior paraolivary nucleus, medial superior olivary nucleus, ventral nucleus of the trapezoid body, lateral dorsal tegmental nucleus, accessory trigeminal nucleus, solitary nucleus, nucleus ambiguus, paratrigeminal nucleus, area postrema, lateral reticular nucleus, and ventrolateral region of the reticular formation. Fiber systems are present that conform to many of the known output systems of these nuclei, including major descending pathways (e.g., striatonigral, striatopallidal, reticulospinal, hypothalamospinal pathways), short projection systems (e.g., mossy fibers in hippocampus, hypothalamo-hypophyseal pathways), and local circuit pathways (e.g., in cortex, hypothalamus). The distribution of MERGL was, with a few notable exceptions, in the same nuclei as DYN B. From these neuroanatomical data, it appears that the dynorphin and enkephalin peptides are strategically located in brain regions that regulate extrapyramidal motor function, cardiovascular and water balance systems, eating, sensory processing, and pain perception.

Dynorphin levels in parkinsonian patients: Leu5-enkephalin production from either proenkephalin A or prodynorphin in human brain

When measured in postmortem parkinsonian brains, dynorphin levels were unchanged, as compared to control brains, in mesencephalic, striatal and corticolimbic areas. A significant reduction in Leu5-enkephalin and Met5-enkephalin levels had been previously observed in the pallidum and putamen whereas only Met5-enkephalin concentrations were decreased in the substantia nigra of parkinsonian brains. These data suggest that L-Enk could be generated either from proenkephalin A in the striatal areas or from prodynorphin in the nigral areas.

Prodynorphin peptide immunocytochemistry in rhesus monkey brain

The present study describes the immunocytochemical distribution of peptides derived from the prodynorphin precursor in the brain of the rhesus monkey (Macaca mulatta). Animals were treated with colchicine (intracerebroventricularly) prior to perfusion to enhance the observation of perikaryal immunoreactivity. Using antisera generated against dynorphin A(1-17), dynorphin B(1-13), and prodynorphin(186-208) (or bridge peptide), the anatomical distribution of dynorphin systems was mapped. The results indicate a widespread neuronal localization of immunoreactivity from the cerebral cortex to the caudal medulla. Anti-dynorphin B and anti-bridge peptide sera proved useful for the demonstration of neuronal perikarya, while the dynorphin A antiserum was best for localizing terminal projection fields. Immunoreactive perikarya are located in numerous brain loci, including the cingulate cortex, caudate nucleus, amygdala, hypothalamus (especially the magnocellular nuclei), thalamus, substantia grisea centralis, parabrachial nucleus, nucleus tractus solitarius, and other nuclei. In addition, fiber and terminal immunoreactivity are seen in varying densities in the striatum and pallidum, substantia innominata, hypothalamus, substantia nigra pars reticulata, parabrachial nucleus, spinal trigeminal nucleus, and other areas. The distribution of prodynorphin peptides in the brain of the monkey is similar to that described for the rat brain; however, significant differences also exist. Other interspecies differences in the anatomy of prodynorphin and proenkephalin neuronal systems in the monkey and human brain are further discussed.

Lesions of the globus pallidus and striatum attenuate ketocyclazocine-induced feeding

A large body of evidence suggests that endogenous opioids are involved in the regulation of feeding. As the striatum and globus pallidus have relatively high concentrations of opioid receptors, these areas are possible sites of action for the stimulatory effects of opiates on feeding. To test these possibilities, male rats were lesioned bilaterally in the globus pallidus or striatum. Nocturnal food intake was then measured after the subcutaneous administration of the opiate antagonist, naloxone (0-10 mg/kg). Spontaneous daytime intake was measured after the subcutaneous administration of the kappa opiate agonist ketocyclazocine (0-10 mg/kg). Neither pallidal nor striatal lesions affected the sensitivity of naloxone in reducing food intake. On the other hand, both lesioned groups were 10-100 times less sensitive to the stimulatory effects of ketocyclazocine. These results suggest that the globus pallidus and striatum may be target areas for the stimulatory effects of exogenous opiates on food intake. Additionally, the relationship of these areas to the dopaminergic nigrostriatal tract suggests that feeding regulation may involve an interaction between dopaminergic and opioid systems.