Huntingtin inclusions do not down-regulate specific genes in the R6/2 Huntington's disease mouse

Transcriptional dysregulation is a central pathogenic mechanism in Huntington's disease (HD); HD and transgenic mouse models of HD demonstrate down-regulation of specific genes at the level of mRNA expression. Furthermore, neuronal intranuclear inclusions (NIIs) have been identified in the brains of R6/2 mice and HD patients. One possibility is that NIIs contribute to transcriptional dysregulation by sequestering transcription factors. We therefore assessed the relationship between NIIs and transcriptional dysregulation in the R6/2 mouse, using double-label in situ hybridization combined with immunohistochemistry, and laser capture microdissection combined with quantitative real-time PCR. There was no difference in transcript levels of specific genes between NII-positive and NII-negative neurons. These results demonstrate that NIIs do not cause decreases in D2, PPE and PSS mRNA levels in R6/2 striatum and therefore are not involved in the down-regulation of these specific genes in this HD model. In addition, these observations argue against the notion that NIIs protect against transcriptional dysregulation in HD.

Gene expression profiling in the post-mortem human brain--no cause for dismay

Global expression profiling techniques such as microarray technology promise to revolutionize biology. Soon it will be possible to investigate alterations at the transcript level of the entire human genome. There is great hope that these techniques will at last shed light on the pathological processes involved in complex neuropsychiatric disorders such as schizophrenia. These scientific advances in turn have re-kindled a great interest and demand for post-mortem brain tissue. Good quality post-mortem tissue undoubtedly is the fundamental prerequisite to investigate complex brain disorders with molecular profiling techniques. In this review we show that post-mortem brain tissue can yield good quality mRNA and intact protein antigens which allow the successful application of traditional molecular biology methods as well as novel profiling techniques. We also consider the use of laser-capture microdissection on post-mortem tissue. This recently developed technique allows the experimenter to explore the molecular basis of cellular function at the single cell level. The combination of laser-capture microdissection with high throughput profiling techniques offers opportunities to obtain precise genetic fingerprints of individual neurons allowing comparisons of normal and pathological states.

New insights into progressive supranuclear palsy

Increased oxidative damage and mitochondrial dysfunction have been suggested to play crucial roles in the pathogenesis of several neurodegenerative diseases, including Parkinson's disease and Alzheimer's disease. In this review, we will focus on progressive supranuclear palsy (PSP), a rare parkinsonian disorder with tau pathology. Particular emphasis is placed on the genetic and biochemical data that has emerged, offering new perspectives into the pathogenesis of this devastating disease, especially the contributory roles of oxidative damage and mitochondrial dysfunction.

Localization of dopaminergic markers in the human subthalamic nucleus

The potential role for dopamine in the subthalamic nucleus was investigated in human postmortem tissue sections by examining; (1) immunostaining for tyrosine hydroxylase, the rate-limiting enzyme in catecholamine synthesis; (2) binding of [(3)H]-SCH23390 (D1-like), [(3)H]-YM-09151-2 (D2-like), and [(3)H]-mazindol (dopamine uptake); and (3) expression of dopamine D1 and D2 receptor mRNAs. Immunostaining for tyrosine hydroxylase was visualized in Bouin's-fixed tissue by using a monoclonal antibody and the avidin-biotin-complex method. The cellular localization of the dopamine D1 and D2 receptor mRNAs was visualized by using a cocktail of human specific oligonucleotide probes radiolabeled with (35)S-dATP. Inspection of immunostained tissue revealed a fine network of tyrosine hydroxylase-immunostained fibers traversing the nucleus; no immunopositive cells were detected. Examination of emulsion-coated tissue sections processed for D1 and D2 receptor mRNA revealed, as expected, an abundance of D1 and D2 mRNA-positive cells in the caudate nucleus and putamen. However, no D1 or D2 receptor mRNA-expressing cells were detected in the subthalamic nucleus. Further, semiquantitative analysis of D1-like, D2-like and dopamine uptake ligand binding similarly revealed an enrichment of specific binding in the caudate nucleus and putamen but not within the subthalamic nucleus. However, a weak, albeit specific, signal for [(3)H]-SCH23390 and [(3)H]-mazindol was detected in the subthalamic nucleus, suggesting that the human subthalamic nucleus may receive a weak dopaminergic input. As weak D1-like binding is detected in the subthalamic nucleus, and subthalamic neurons do not express dopamine D1 or D2 receptor mRNAs, together these data suggest that the effects of dopaminergic agents on the activity of human subthalamic neurons may be indirect and mediated via interaction with dopamine D1-like receptors.

Frontal lobe dysfunction in progressive supranuclear palsy: evidence for oxidative stress and mitochondrial impairment

Recent data from our laboratory have shown a regionally specific increase in lipid peroxidation in postmortem progressive supranuclear palsy (PSP) brain. To extend this finding, we measured activities of mitochondrial enzymes as well as tissue malondialdehyde (MDA) levels in postmortem superior frontal cortex (Brodmann's area 9; SFC) from 14 pathologically confirmed cases of PSP and 13 age-matched control brains. Significant decreases (-39%) in alpha-ketoglutarate dehydrogenase complex/glutamate dehydrogenase ratio and significant increases (+36%) in tissue MDA levels were observed in the SFC in PSP; no differences in complex I or complex IV activities were detected. Together, these results suggest that mitochondrial dysfunction and lipid peroxidation may underlie the frontal metabolic and functional deficits observed in PSP.

Expression of alpha-synuclein, parkin, and ubiquitin carboxy-terminal hydrolase L1 mRNA in human brain: genes associated with familial Parkinson's disease

Mutations in the alpha-synuclein, parkin, and ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) genes have been linked to some cases of familial Parkinson's disease. To provide insight into how these genes may relate to each other and contribute to the pathology of Parkinson's disease, their expression was examined in normal human brain. Tissue sections from multiple regions of 11 normal human brains were hybridized with radiolabeled and digoxygenin-labeled cRNA probes for alpha-synuclein, parkin, and UCH-L1 mRNA. Expression of each of these three genes was predominantly neuronal. Alpha-synuclein and parkin mRNAs were expressed in a restricted number of brain regions, whereas UCH-L1 mRNA was more uniformly expressed throughout brain. The melanin-containing dopamine neurons of the substantia nigra had particularly robust expression. The expression patterns of alpha-synuclein and parkin mRNAs were similar, suggesting that these two proteins may be involved in common pathways contributing to the pathophysiology of Parkinson's disease.

Distribution of the mRNAs encoding torsinA and torsinB in the normal adult human brain

To gain insight into the neural pathways involved in the pathogenesis of DYT1 dystonia, we have mapped the cellular expression of the mRNA encoding torsinA and the closely related family member, torsinB, in normal adult human brain. Here, we report an intense expression of torsinA mRNA in the substantia nigra pars compacta dopamine neurons, the locus ceruleus, the cerebellar dentate nucleus, Purkinje cells, the basis pontis, numerous thalamic nuclei, the pedunculopontine nucleus, the oculomotor nucleus, the hippocampal formation, and the frontal cortex. Within the caudateputamen, the cellular expression of torsinA mRNA was heterogeneous; a moderate signal was found overlying large cholinergic neurons, and most striatal neurons exhibited only a very weak signal. A moderate signal was detected in numerous midbrain and hindbrain nuclei. A weak cellular signal was detected in neurons of the globus pallidus and subthalamic nucleus. In marked contrast to torsinA, no specific mRNA signal was detected for torsinB. That torsinA mRNA is enriched in several basal ganglia nuclei, including the dopamine neurons in the substantia nigra, is intriguing since it suggests that DYT1 dystonia may be associated with a dysfunction in dopamine transmission.

Measurement of GABAergic parameters in the prefrontal cortex in schizophrenia: focus on GABA content, GABA(A) receptor alpha-1 subunit messenger RNA and human GABA transporter-1 (HGAT-1) messenger RNA expression

The hypothesis that the pathophysiology of schizophrenia may be associated with a dysfunction in GABA transmission in the human prefrontal cortex was investigated. Human post mortem brain tissue from 10 control cases and six cases of schizophrenia were processed for amino acid analysis and for radioactive in situ hybridization. Laminae III and V of three prefrontal cortical areas were examined in detail, namely Brodmann areas 9, 10 and 11. Of these three areas significant changes in GABAergic markers were found only in areas 9 and 10. Of note, a significant decrease in the tissue content of GABA was observed and this was accompanied by a marked increase in the cellular expression of the GABA(A) receptor alpha-1 subunit messenger RNA and a marked decrease in the expression of human GABA transporter-1, the messenger RNA encoding the neuronal GABA transporter protein. The amino acid analysis data provided in this study coupled with the detailed cellular study of several GABAergic markers in the human prefrontal cortex provide direct evidence in support of a disturbance in GABA transmission in the prefrontal cortex, which may be loosely termed "hypofrontality".

Evidence for oxidative stress in the subthalamic nucleus in progressive supranuclear palsy

Increased free radical production and oxidative stress have been proposed as pathogenic mechanisms in several neurodegenerative disorders. Free radicals interact with biological macromolecules, such as lipids, which can lead to lipid peroxidation. A well-established marker of oxidative damage to lipids is malondialdehyde (MDA). We measured tissue MDA levels in the subthalamic nucleus (STN) and cerebellum from 11 progressive supranuclear palsy (PSP) cases and 11 age-matched control cases using sensitive HPLC techniques. In PSP, a significant increase in tissue MDA levels was observed in the STN when compared with the age-matched control group. By contrast, no significant difference between tissue MDA content was observed in cerebellar tissue from the same PSP and age-matched control cases. These results indicate that lipid peroxidation may play a role in the pathogenesis of PSP.

Localization of calcium-binding proteins and GABA transporter (GAT-1) messenger RNA in the human subthalamic nucleus

The distribution of messenger RNA encoding the human GAT-1 (a high-affinity GABA transporter) was investigated in the subthalamic nucleus of 10 neurologically normal human post mortem cases. Further, the distribution of messenger RNA and protein encoding the three neuronally expressed calcium-binding proteins (calbindin D28k, parvalbumin and calretinin) was similarly investigated using in situ hybridization and immunohistochemical techniques. Cellular sites of calbindin D28k, parvalbumin, calretinin and GAT-1 messenger RNA expression were localized using human-specific oligonucleotide probes radiolabelled with [35S]dATP. Sites of protein localization were visualized using specific anti-calbindin D28k, anti-parvalbumin and anti-calretinin antisera. Examination of emulsion-coated tissue sections processed for in situ hybridization revealed an intense signal for GAT-1 messenger RNA within the human subthalamic nucleus, indeed the majority of Methylene Blue-counterstained cells were enriched in this transcript. Further, a marked heterogeneity was noted with regard to the expression of the messenger RNA's encoding the three calcium-binding proteins; this elliptical nucleus was highly enriched in parvalbumin messenger RNA-positive neurons and calretinin mRNA-positive cells but not calbindin messenger RNA-positive cells. Indeed, only an occasional calbindin messenger RNA-positive cell was detected within the mediolateral extent of the nucleus. In marked contrast, numerous parvalbumin messenger RNA-positive cells and calretinin messenger RNA-positive cells were detected and they were topographically distributed; parvalbumin messenger RNA-positive cells were highly enriched in the dorsal subthalamic nucleus extending mediolaterally; calretinin messenger RNA-positive cells were more enriched ventrally although some degree of overlap was apparent. Computer-assisted analysis of the average cross-sectional somatic area of parvalbumin, calretinin and GAT-1 messenger RNA-positive neurons revealed them all to be in the range of 300 microm2. The unique patterns of calcium-binding protein gene expression were similarly reflected at the protein level; an abundance of parvalbumin- and calretinin-immunopositive neurons were observed whereas only occasional intensely-labelled calbindin-immunopositive fibres were seen, no calbindin-immunopositive cells were detected. Single and double labelling studies show that parvalbumin-immunopositive neurons were mainly localized in the dorsal region of the nucleus, and calretinin-immunopositive neurons were mainly localized in the ventral region although there was overlap with double-labelled neurons located in the middle and dorsal regions. The significance of these findings, in particular the expression of GAT-1, a high-affinity GABA uptake protein, for basal ganglia signalling is discussed.

Expression of the early-onset torsion dystonia gene (DYT1) in human brain

Early-onset torsion dystonia, an autosomal dominant disease associated with the DYT1 locus on 9q34, is the most frequent genetic form of dystonia. Recent work has revealed that the causative mutation in most cases is deletion of a glutamate residue from the carboxy terminal of torsinA, a 332 amino acid protein encoded by the DYT1 gene. To gain insight into how deletion of a single amino acid can produce such a profound movement disorder, we have mapped the expression of the DYT1 gene in normal human postmortem brain. DYT1 mRNA is highly enriched in the dopamine neurons of the substantia nigra pars compacta. Intense expression was also found in the cerebellum and hippocampal subfields. The prominent expression of the DYT1 gene within the substantia nigra pars compacta, which provides dopaminergic innervation to the basal ganglia, implicates a disturbance of dopaminergic function in the pathophysiology of early-onset torsion dystonia.

Expression of the human excitatory amino acid transporter 2 and metabotropic glutamate receptors 3 and 5 in the prefrontal cortex from normal individuals and patients with schizophrenia

A disturbance of glutamatergic transmission has been suggested to contribute to the development of schizophrenic pathophysiology based primarily on the ability of glutamate receptor antagonists to induce schizophrenic-like symptoms, and recent studies suggesting reduced glutamatergic function in the prefrontal cortex (PFC) of individuals with a diagnosis of schizophrenia. In order to investigate this hypothesis further, the expression of several 'glutamatergic' markers, the metabotropic glutamate receptors (mGluRs; mGluR3, 5) and the human excitatory amino acid transporter (EAAT2) were compared in the PFC of normal individuals and schizophrenics. The present results showed that glial cells in the pyramidal layers of the PFC from schizophrenics had decreased EAAT2 mRNA content relative to controls in Brodmann areas 9 and 10. The cellular levels of expression of the two mGluR signals investigated (mGluR3, and 5) were not significantly changed relative to controls except for an increase in the neuronal mGluR5 in the pyramidal cell layers of area 11. Comparing the ratio of cellular mGluR expression to that of EAAT2, the mGluR/EAAT2 ratio showed that schizophrenics had a significantly increased mGluR/EAAT2 ratios in the pyramidal cell layers of all three PFC regions examined. The glutamate content of consecutive sections analyzed by high pressure liquid chromatography (HPLC), although decreased in schizophrenics did not reach significance and did not correlate with either EAAT2 or mGluR mRNA content. These results are discussed in the light of current results on the neurochemistry and pharmacology of schizophrenia.

Contrasting effects of excitotoxic lesions of the prefrontal cortex on the behavioural response to D-amphetamine and presynaptic and postsynaptic measures of striatal dopamine function in monkeys

The effects of excitotoxic lesions of the prefrontal cortex on behavioural, neurochemical and molecular indices of dopamine function in the caudate nucleus were studied in the marmoset. The lesion, which encompassed both the lateral and orbital regions of prefrontal cortex, made the animals more sensitive to the performance disrupting effects of the dopamine releasing drug, D-amphetamine, in a variation of the object retrieval task. Specifically, following drug administration, the lesioned marmosets were less able to gain access to food reward in the minimum number of responses. Analysis of the nature of the errors suggested that the deficit was not due to inhibition of a prepotent response as the lesioned monkeys were just as likely to make a detour reach to the unopened side of the box as a direct "line-of-sight" reach into the unopened front of the box. Rather, the data indicated a general disorganization of behaviour. The enhanced behavioural responsiveness to manipulations increasing presynaptic dopamine function was accompanied by neurochemical changes indicating a reduced responsiveness, as revealed by in vivo microdialysis. Thus, in lesioned animals, whilst there were no effects on baseline levels of extracellular dopamine in dorsolateral caudate, evoked release, both to systemic D-amphetamine and to a local depolarizing pulse of potassium ions, was attenuated. These opposite effects of the prefrontal cortex lesion on behavioural and neurochemical indices of striatal dopamine function occurred in the absence of any changes in striatal dopamine receptors of the D1 and D2 subtype, as determined both by radioligand binding assays and measurements of messenger RNA using in situ hydridization techniques. These data provide further insight into the interactions between prefrontal cortex and striatal dopamine function in the non-human primate. In particular, when taken in the light of our previous studies they indicate that following prefrontal manipulations, concurrence between behavioural and neurochemical indices of striatal dopamine function depends, critically, on the behavioural task. These findings are discussed with respect to the growing body of evidence implicating abnormalities in frontostriatal neurotransmission in complex disorders such as schizophrenia.

Dopamine D1 and D2 receptor gene expression in the striatum in Huntington's disease

The cellular expression of dopamine D1 and D2 receptor mRNAs was investigated in the postmortem human caudate nucleus of control cases and genetically and pathologically confirmed cases of Huntington's disease (HD) by using quantitative in situ hybridization. The HD cases were categorized (0-4) by severity of striatal neuropathology according to the Vonsattel scale. For the HD grade 0 case, a pronounced reduction in the number of D1 and D2 mRNA-positive cells was observed compared with controls; however, the abundance of both receptor mRNAs per remaining cell was within the control range. For D2 receptor mRNA, the number of detectable D2-positive medium-sized cells decreased with increasing pathology; this decrease was accompanied by a gradual reduction in the intensity of D2 signal per cell. By contrast, for D1 receptor mRNA, despite a decrease in the number of D1 mRNA-positive cells detected, the average cellular expression of D1 mRNA was markedly reduced in the HD grade 1 case and then increased (relative to the grade 1 case) with increasing pathology, presumably reflecting the relative survival of D1-expressing striatal interneurons. The implications of these findings for providing further information on the neurodegenerative process in HD are discussed.

Monoamine transporter gene expression in the central nervous system in diabetes mellitus

Diabetic animals exhibit altered neurotransmission in brain monoaminergic systems. By means of in situ hybridization, we have investigated the expression of dopamine, noradrenaline, and serotonin transporter (DA-T, NA-T, and 5-HT-T, respectively) mRNAs in the brains of alloxan- and streptozotocin-diabetic rats. The expression of DA-T mRNA is decreased in 1- (-11%) and 4- (-17%) week alloxan-diabetic and 4- (-9%) and 8- (-20%) week streptozotocin-diabetic rats in the ventral medial bundle. The expression of NA-T mRNA is decreased in the locus coeruleus of 8- (-26%) week streptozotocin-diabetic rats, in the noradrenergic A1 cell group of 4- (-27%) week alloxan- and 8- (-25%) week streptozotocin-diabetic rats, and in the noradrenergic A2 cell group of 1- (-21%) and 4- (-28%) week alloxan-diabetic and 4- (-27%) and 8- (-25%) week streptozotocin-diabetic animals. The expression of 5-HT-T mRNA in the dorsal raphe nucleus is increased in 1- (+14%) and 4- (+44%) week alloxan- and 4- (+28%) and 8- (+44%) week streptozotocin-diabetic rats. The expression of each of the three monoamine transporter genes may be differentially regulated in diabetes and dependent on the duration of diabetes. Altered monoamine transporter gene expression may possibly contribute to the observed dysfunctions in brain monoamine transmission in chronic diabetes.

Phenotypic characterization of neurotensin messenger RNA-expressing cells in the neuroleptic-treated rat striatum: a detailed cellular co-expression study

The chemical phenotype of proneurotensin messenger RNA-expressing cells was determined in the acute haloperidol-treated rat striatum using a combination of (35S)-labelled and alkaline phosphatase-labelled oligonucleotides. Cellular sites of proneurotensin messenger RNA expression were visualized simultaneously on tissue sections processed to reveal cellular sites of preproenkephalin A messenger RNA or the dopamine and adenylate cyclase phosphoprotein-32, messenger RNA. The cellular co-expression of preproenkepahlin A (enkephalin) and preprotachykinin (substance P) messenger RNA was also examined within forebrain structures. Cellular sites of enkephalin (substance P) and dopamine and adenylate cyclase phosphoprotein-32 messenger RNAs were visualized using alkaline phosphatase-labelled oligonucleotides whilst sites of substance P and proneurotensin messenger RNA expression were detected using (35S)-labelled oligos. Cellular sites of enkephalin and dopamine and adenylate cyclase phosphoprotein-32 gene expression were identified microscopically by the concentration of purple alkaline phosphatase reaction product within the cell cytoplasm, whereas sites of substance P and proneurotensin gene expression were identified by the dense clustering of silver grains overlying cells. An intense hybridization signal was detected for all three neuropeptide messenger RNAs in the striatum, the nucleus accumbens and septum. Dopamine and adenylate cyclase phosphoprotein-32 messenger RNA was detected within the neostriatum but not within the septum. In all forebrain regions examined, with the exception of the islands of Calleja, the cellular expression of enkephalin messenger RNA and substance P messenger RNA was discordant; the two neuropeptide messenger RNAs were detected essentially in different cells, although in the striatum and nucleus accumbens occasional isolated cells were detected which contained both hybridization signals; dense clusters of silver grains overlay alkaline phosphatase-positive cells, demonstrating clearly that these dual-labelled cells expressed both messenger RNAs. By contrast, the hybridization signals for proneurotensin and enkephalin, and proneurotensin and dopamine and adenylate cyclase phosphoprotein-32 were generally coincident, at least within the neostriatum; most proneurotensin messenger RNA-positive cells expressed enkephalin messenger RNA and were also positive for dopamine and adenylate cyclase phosphoprotein-32 messenger RNA. However, occasional proneurotensin messenger RNA-positive striatal cells were identified that were single-labelled and did not express enkephalin messenger RNA. Within the septal nucleus, enkephalin messenger RNA and substance P messenger RNA were expressed essentially within segregated cell populations. These studies illustrate further the utility of co-expression techniques for investigating the chemical phenotype of cells within the CNS and demonstrate that the distribution of neuropeptide co-expressing cells is different within different brain regions. That several populations of proneurotensin messenger RNA-positive striatal cells may exist, of which one population is sensitive to haloperidol, co-expresses enkephalin messenger RNA and is positive for dopamine and adenylate cyclase phosphoprotein-32 messenger RNA may be of some significance in neuropsychiatric/neurological disorders given that the translated peptide, neurotensin, is known to influence and interact closely with the dopamine systems.

Effects of L-DOPA-therapy on dopamine D2 receptor mRNA expression in the striatum of MPTP-intoxicated parkinsonian monkeys

The cellular expression of dopamine D2 receptor mRNA was examined in striatal (caudate nucleus and putamen) neurones of 9 Macaca fascicularis monkeys rendered parkinsonian by systemic injection of MPTP. Messenger RNA abundance was determined by quantitative in situ hybridization using human-specific 35S-labelled oligonucleotides. Control monkeys were untreated and received neither MPTP nor L-DOPA while the rest were rendered parkinsonian and received chronic levodopa therapy to induce dyskinesia. In the control brains a strong dopamine D2 receptor hybridization signal was detected overlying medium-sized and some large neurons in both the caudate nucleus and putamen. Neurons from the lateral and medial regions of the caudate nucleus, and from the dorsal and ventral regions of the putamen were analysed separately. A significant increase in the cellular abundance of dopamine D2 receptor mRNA was seen in the striatum of MPTP-treated monkeys; this increase being restricted to the population of medium-sized striatal cells. No such increase in dopamine D2 receptor mRNA was observed in (dyskinetic) L-DOPA-treated monkeys suggesting that levodopa-therapy normalises D2 receptor expression in post-synaptic striatal cells. The cellular abundance of dopamine D2 receptor mRNA expressed by large striatal neurons (putative cholinergic cells) was unaffected by either MPTP treatment or levodopa therapy. The implications of these findings for the development of levodopa-induced dyskinesias is discussed.

Reduction in enkephalin and substance P messenger RNA in the striatum of early grade Huntington's disease: a detailed cellular in situ hybridization study

The expression of enkephalin and substance P messenger RNAs was examined in the caudate-putamen of human post mortem tissue from control and Huntington's disease tissue using in situ hybridization techniques and human specific enkephalin and substance P [35S] oligonucleotides. Macroscopic and microscopic quantification of enkephalin and substance P gene expression was carried out using computer-assisted image analysis. Tissue was collected from six control cases with no sign of neurological disease and six Huntington's disease cases ranging from grades 0 to 3 as determined by neuropathological evaluation. The clinical and pathological diagnosis of Huntington's disease was confirmed unequivocally by genetic analysis of the CAG repeat length in both copies of IT15, the Huntington's disease gene. A marked reduction in both enkephalin and substance P messenger RNAs was detected in all regions of the caudate nucleus and putamen in Huntington's disease grades 2/3 when compared to controls; in the dorsal caudate few enkephalin or substance P messenger RNA-positive cells were detected. For the early grade (0/1) Huntington's disease cases, a heterogeneous reduction in both enkephalin and substance P messenger RNAs were noted; for enkephalin messenger RNA the striatal autoradiograms displayed a conspicuous patchy appearance. Detailed cellular analysis of the dorsal caudate revealed a striking reduction in the number of enkephalin and substance P messenger RNA-positive cells detected and in the intensity of hybridization signal/cell. These data suggest that both the "indirect" GABA/enkephalin and "direct" GABA/substance P pathways are perturbed very early in the course of the disease and that these early changes in chemical signalling may possibly underlie the onset of clinical symptoms.

Dopamine transporter (Dat) and synaptic vesicle amine transporter (VMAT2) gene expression in the substantia nigra of control and Parkinson's disease

The cellular expression of DAT mRNA and VMAT2 mRNA was investigated in sections of the human post-mortem substantia nigra in control and Parkinson's disease tissue using in situ hybridisation techniques. Short synthetic oligodeoxynucleotides were used to detect these gene transcripts at the cellular level. In the control human nigra, high levels of expression were seen in all sub-divisions of the substantia nigra, especially within medial regions. By contrast, the level of expression of both DAT mRNA and VMAT2 mRNA was markedly reduced in Parkinson's disease; these reductions in hybridisation signal were associated with (i) a marked loss of dopamine-containing cells in the substantia nigra, and (ii) a reduction in both DAT and VMAT2 signal per cell in the remaining pigmented neurones. These disease-related decreases in the cellular abundance of both DAT and VMAT2 gene transcripts in the surviving cells of the parkinsonian nigra may reflect compensatory changes in catecholamine signalling or may be a consequence of neuronal dysfunction.

Striatal interneurones: chemical, physiological and morphological characterization

The neostriatum is the largest component of the basal ganglia, and the main recipient of afferents to the basal ganglia from the cerebral cortex and thalamus. Studies of the cellular organization of the neostriatum have focused upon the spiny projection neurones, which represent the vast majority of neurones, but the identity and functions of interneurones in this structure have remained enigmatic despite decades of study. Recently, the discovery of cytochemical markers that are specific for each of the major classes of striatal interneurones, and the combination of this with intracellular recording and staining, has revealed the identities of interneurones and some of their functional characteristics in a way that could not have been imagined by the classical morphologists. These methods also suggest some possible modes of action of interneurones in the neostriatal circuitry.

Regulation of GABA transporter activity and mRNA expression by estrogen in rat preoptic area

This study has examined whether estrogen regulates GABA transporter synthesis and activity in the female rat brain. In the first experiment in situ hybridization studies examined the effects of ovariectomy on cellular GABA transporter-1 (GAT-1) mRNA content. A 25% decrease in GAT-1 mRNA expression was detected within the medial preoptic area (MPOA) but not the parietal cortex, magnocellular preoptic nucleus (Mg-POA) or caudate-putamen (C-P). Estrogen replacement for 7 d returned GAT-1 mRNA content of MPOA cells to levels observed in intact rats. In the second experiment, the effect of increased brain GABA concentrations on GAT-1 mRNA expression was investigated by treating rats with gamma-vinyl GABA, a GABA-transaminase inhibitor. Although resulting in a twofold increase in tissue GABA content, in situ hybridization experiments revealed no changes in GAT-1 transcript expression. A third series of experiments examined GABA transporter activity in vitro using a 3H GABA uptake assay in MPOA, cortex, and C-P punches. Nipecotic acid (10 microM) reduced specific 3H GABA uptake in all three brain regions while 100 microM beta-alanine only reduced uptake in the MPOA. Estrogen treatment for 7 d resulted in a significant increase in 3H GABA uptake in the MPOA but not the cortex or C-P. The presence of a putative estrogen response element in the GAT-1 gene and the effects demonstrated here on GAT-1 mRNA content and GABA transporter activity indicate that estrogen may influence GAT-1 gene transcription to alter GABA transporter function within the MPOA but not the C-P or cortex.

Dopamine D1 receptor, D2 receptor, proenkephalin A and substance P gene expression in the caudate nucleus of control and schizophrenic tissue: a quantitative cellular in situ hybridisation study

The cellular expression of the mRNAs encoding the dopamine D1 receptor, dopamine D2 receptor and the neuropeptides enkephalin and substance P was determined in fresh frozen sections of human post-mortem caudate nucleus from control and schizophrenic brains using the technique of radioactive in situ hybridisation coupled with computer-assisted image analysis. Measurements of silver grain densities and mean cross-sectional somatic areas revealed no significant differences in the expression of any of these four gene transcripts. Further, cell count estimates revealed that each of these four mRNAs was expressed by approximately 20% of caudate cells (neurones and glia) in both control and schizophrenic tissue. These data demonstrate that the cellular expression of the dopamine D1 and D2 receptors and the neuropeptides enkephalin and substance P mRNAs are stable post mortem and that the relative cellular abundance of these mRNAs is not altered in the caudate nucleus of schizophrenic brains when compared to controls. These findings draw into focus the possible sites of action of clinically prescribed neuroleptics and suggest that chronic neuroleptic treatment of patients displaying negative schizophrenic symptoms may 're-set' an underlying neurochemical imbalance within the caudate nucleus.

Effects of L-DOPA on preproenkephalin and preprotachykinin gene expression in the MPTP-treated monkey striatum

The cellular expression of the genes encoding the neuropeptides enkephalin and substance P were examined in the caudate nucleus and putamen of parkinsonian 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated cynomolgus monkeys by in situ hybridization using radioactive antisense oligonucleotides coupled with computer-assisted image analysis. Behavioural evaluation of the animals revealed two levels of motor impairment; one group moderately impaired and the other severely disabled. A marked increase in the cellular content of preproenkephalin A messenger RNA was observed in medium-sized (106 +/- 9 microns2) cells in the caudate-putamen of all MPTP animals when compared with controls, the increase being greatest in the most severely impaired animals. By contrast, a marked reduction in the cellular abundance of preprotachykinin gene expression was detected in striatal cells (101 +/- 16 microns2) of these same MPTP animals. These changes in neuropeptide gene expression were not associated with a change in the density (approximately 10 cells per mm2) of messenger RNA-expressing cells. L-DOPA treatment of two of the severely-impaired MPTP monkeys resulted in a dissociation of expression of these two genes: the cellular abundance of preproenkephalin A remained elevated whilst preprotachykinin levels were normalized and comparable with controls. No change in the cellular abundance of preprotachykinin messenger RNA was observed in cells of the insular cortex or a small discrete population of large cells (208 +/- 27 microns2) in the ventral putamen. These results demonstrate that MPTP treatment of primates results in a marked potentiation in preproenkephalin messenger RNA coupled with a attenuation in preprotachykinin messenger RNA in the dopamine-denervated caudate-putamen. L-DOPA therapy given on an intermittent schedule reverses the decrease in preprotachykinin messenger RNA, but fails to reverse the increase in preproenkephalin messenger RNA in the same animal. These observations suggest that a dissociation of the activity of these two neuropeptide systems may underlie the improvement in motor skill that accompanies dopamine replacement therapy and that this dissociation may be instrumental in the long-term complications associated with L-DOPA therapy.

Identified cholinergic neurones in the adult rat brain are enriched in GAP-43 mRNA: a double in situ hybridisation study

The cellular expression of growth associated protein-43 mRNA by identified choline acetyl transferase mRNA positive cells was investigated in the mature rat brain using a combined radioactive and non-radioactive in situ hybridisation technique. Cellular sites of growth associated protein-43 mRNA were detected using a 35S-oligonucleotide while choline acetyl transferase mRNA positive neurones were identified using two alkaline phosphatase-labelled probes. In the cholinergic cells of the corpus striatum, basal forebrain and laterodorsal tegmental nucleus a specific growth associated protein-43 hybridisation signal (silver grains) was detected, demonstrating that these choline acetyl transferase mRNA positive cells are enriched in growth associated protein-43 gene transcripts. By contrast, the large cholinergic cells of the motor nucleus of the trigeminal nerve did not express growth associated protein-43 mRNA. Quantification of the growth associated protein-43 hybridisation signal expressed by identified choline acetyl transferase mRNA positive cells showed regional variations in the relative cellular abundance of this transcript; cholinergic cells in the laterodorsal tegmental nucleus and corpus striatum expressed the strongest cellular hybridisation signal. Mean cross-sectional somatic area measurements of these growth associated protein-43/cholinergic positive cells confirmed the identity of these neurones as belonging to the cholinergic phenotype. A strong 35S-growth associated protein-43 hybridisation signal was detected also in numerous other non-choline acetyl transferase mRNA positive nerve cells in other regions of the brain, although the chemical phenotypes of these neurones were not determined. Our data reveal that expression of the growth-associated protein GAP-43 is maintained in identified cholinergic neurones in the postnatal rat brain, suggesting that this protein may subserve important functions in cholinergic and other neurones of the adult mammalian brain.

Localization of GAT-1 GABA transporter mRNA in rat striatum: cellular coexpression with GAD67 mRNA, GAD67 immunoreactivity, and parvalbumin mRNA

The cellular localization and neurochemical phenotype of cells expressing the GAT-1 GABA transporter was investigated in the adult rat dorsal striatum using single and dual in situ hybridization and immunocytochemical techniques. Cellular sites of GAT-1, GAD67, and parvalbumin mRNAs were visualized using a combination of radioactive and alkaline phosphatase-labeled oligonucleotides and emulsion autoradiography; GAD67 immunoreactivity was detected using a polyclonal antibody (K2) and 3'3"-diaminobenzidine. Two types of GAT-1-positive striatal cells were detected: (1) those expressing an abundance of GAT-1 mRNA, and (2) those expressing low/undetectable amounts of message. This study focused on the striatal cells expressing an abundance of GAT-1 mRNA; these cells accounted for approximately 3-5% of all striatal neurons and were detected scattered sparsely throughout the striatal complex. Dual in situ hybridization and immunocytochemical studies established that all cells enriched in GAT-1 mRNA also expressed high levels of GAD67 mRNA and were strongly GAD67 immunopositive; the converse was also found to be the case, the two hybridization signals having identical distribution patterns. Further dual in situ hybridization studies established that approximately 60% of these high GAD67/GAT-1 cells expressed parvalbumin mRNA, a marker of one population of striatal interneurons, and had an average cross-sectional area of 152.40 microns 2. The chemical phenotype of the remaining 40% of high GAD67/GAT-1 cells was not determined, although the average cross-sectional area of these cells (102.48 microns 2) was significantly smaller than GAT-1/GAD67/parvalbumin cells; these cells were detected in all striatal regions and are likely to correspond to another population of striatal GABAergic interneuron.

Expression of GABAA receptor alpha 2 sub-unit mRNA by periventricular somatostatin neurones in the rat hypothalamus

Pharmacological evidence suggests that GABA may play an important role in regulating the secretory and synthetic activity of the hypothalamic periventricular somatostatin (SOM) neurones controlling growth hormone secretion. In this study, we have utilized a dual labelling in situ hybridization technique to examine whether the alpha 2 sub-unit of the GABAA receptor, which is abundant in this region, is expressed by periventricular SOM neurones. Neurones expressing SOM were detected using an alkaline phosphatase-labelled antisense oligonucleotide and the alpha 2 sub-unit with an 35S-labelled antisense oligonucleotide. Hybridization experiments with the alpha 2 sub-unit probe alone confirmed the high level of mRNA expression for this sub-unit in the rat periventricular region and simultaneous hybridization experiments with both probes revealed that > 90% (93 +/- 2%) of periventricular SOM neurones express the alpha 2 sub-unit of the GABAA receptor. These results provide the first direct evidence that periventricular SOM cells possess GABAA receptors and suggest that the great majority of these neurones synthesize a GABAA receptor containing the alpha 2 sub-unit.

Expression of N-methyl-D-aspartate receptor subunit NR1 messenger RNA by identified striatal somatostatin cells

At present it is not clear whether N-methyl-D-aspartate and N-methyl-D-aspartate receptor agonists have a direct excitotoxic effect on somatostatin interneurons in rat striatum. The N-methyl-D-aspartate receptor comprises a multivariant complex encoded by a family of subunit complementary DNAs. Evidence suggests that expression of the N-methyl-D-aspartate receptor subunit NR1 (zeta 1) is essential for functional receptors. To investigate the expression of NR1 messenger RNA by striatal somatostatin cells, a dual in situ hybridization technique was applied to fresh frozen tissue sections. Cellular sites of NR1 and somatostatin gene expression were visualized in the same tissue section using [35S]NR1 and alkaline phosphatase-labelled somatostatin oligonucleotides. Only 8-18% of striatal somatostatin cells expressed a strong NR1 hybridization signal; most cells (> 80%) expressed a weak or undetectable signal. In contrast NR1 messenger RNA was enriched in neighbouring medium-sized non-somatostatin cells. These data suggest that while the NR1 gene is expressed in some striatal somatostatin cells most do not express a strong NR1 signal, a finding which may explain, in part, the preferential survival of somatostatin cells in Huntington's disease.

Adenosine A2a receptor mRNA is expressed by enkephalin cells but not by somatostatin cells in rat striatum: a co-expression study

The cellular co-expression of adenosine A2a receptor mRNA and preproenkephalin A (PPE A) mRNA and A2a receptor mRNA and prosomatostatin (pSRIF) mRNA in rat striatum was studied using a combination of radioactive and non-radioactive in situ hybridization techniques. Cells containing adenosine A2a receptor mRNA were visualised using an 35S-labelled oligonucleotide whilst those containing PPE A mRNA and pSRIF mRNA were detected using alkaline phosphatase-labelled antisense oligonucleotides; both radioactive and non-radioactive hybridization signals were visualized on the same tissue section. Bright field examination of striatal sections hybridized with both the [35S]adenosine A2a receptor probe and the alkaline phosphatase-labelled PPE A probe revealed dense clusters of silver grains overlying cells containing alkaline phosphatase reaction product demonstrating that the two gene transcripts were expressed by the same medium-sized nerve cells. The cellular expression of the two mRNAs was consistently found to be concordant demonstrating that adenosine A2a receptor mRNA is expressed by medium-sized striatal enkephalin cells. In contrast, clusters of silver grains were never detected overlying striatal cells containing pSRIF mRNA indicating that this population of interneurones do not express the adenosine A2a receptor sub-type. The expression of adenosine A2a receptors by enkephalin cells in striatum suggests that adenosine may play a role in modulating the activity of GABA/enkephalin striatopallidal neurones through interaction with A2a receptors.

Co-expression of dopamine transporter mRNA and tyrosine hydroxylase mRNA in ventral mesencephalic neurones

Radioactive in situ hybridization was used to map the cellular localization of dopamine (DA) transporter mRNA-containing cells in the adult rat central nervous system. The distribution of DA transporter mRNA-containing cells was compared to adjacent sections processed to visualize tyrosine hydroxylase (TH) mRNA, a marker of catecholamine containing neurones. TH mRNA-containing cells, visualized using an alkaline phosphatase labelled probe, were detected in the hypothalamus, midbrain and pons; the strongest hybridization signals being detected in the substantia nigra, ventral tegmental area and locus coeruleus. The distribution of DA transporter mRNA-containing cells was more restricted; a strong signal being detected in the substantia nigra pars compacta and ventral tegmental area only. No hybridization signal was detected in the locus coeruleus. By simultaneously hybridizing mesencephalic tissue with both the alkaline phosphatase-labelled TH probe and the 35S-labelled DA transporter probe we were able to demonstrate that both DA transporter and TH mRNAs are expressed by the same cells in the substantia nigra and ventral tegmental area. The restricted anatomical localization of DA transporter mRNA-containing cells and the lack of expression in the locus coeruleus and other adrenergic and noradrenergic cell groups confirms the DA transporter as a presynaptic marker of DA containing nerve cells in the rat brain.

Expression of glutamic acid decarboxylase messenger RNA in rat medial preoptic area neurones during the oestrous cycle and after ovariectomy

Evidence suggests that medial preoptic area (MPOA) neurones containing gamma-aminobutyric acid (GABA) are modulated directly by oestrogen. We have used an alkaline phosphatase-labelled antisense oligonucleotide probe to examine glutamic acid decarboxylase67 (GAD) mRNA expression within individual cells of the MPOA, diagonal band of Broca (DBB) and parietal cortex in rats killed at noon on each day of the oestrous cycle and after ovariectomy (n = 4-5). As a fall in extracellular GABA concentrations occurs in the MPOA on the afternoon of proestrus, the GAD67 mRNA content of cells was also examined in proestrous rats at 15:00h immediately prior to the preovulatory luteinising hormone (LH) surge. The MPOA was found to have an intermediate number of GAD67 mRNA-containing cells compared with the DBB and cortex (P less than 0.01) but expressed the lowest mean hybridisation signal (P less than 0.01). The parietal cortex had significantly fewer (P less than 0.01) GAD mRNA-containing cells than either the MPOA or DBB but these contained higher mean density of signal (P less than 0.01). The hybridisation signal for GAD mRNA was abolished by either ribonuclease pre-treatment or the use of excess non-labelled probe. No significant (P greater than 0.05) differences in GAD67 mRNA were detected in animals killed at noon throughout the oestrous cycle or after ovariectomy. On the afternoon of proestrus (15:00h) there was a significant 40% reduction in mean GAD67 mRNA content within cells of only the MPOA compared with noon (P less than 0.05). The numbers of cells in the MPOA expressing GAD67 mRNA were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Pertussis toxin administration increases the expression of proneurotensin and preproenkephalin A mRNAs in rat striatum

The effect of a unilateral intrastriatal microinjection of pertussis toxin on the expression of proneurotensin and preproenkephalin A mRNAs in the adult rat neostriatum was investigated using a technique of non-radioactive in situ hybridization. Control sham microinjected animals received an equal volume of vehicle only and were processed in parallel with the pertussis toxin-treated rats. All rats were allowed to recover from the stereotaxic surgery for 22 h before being killed and their brains rapidly removed and processed for in situ hybridization using alkaline phosphatase-labelled oligonucleotide probes. In comparison to sham microinjected rats, a single intrastriatal microinjection of pertussis toxin (1 microgram) resulted in a significant increase in the amount of both proneurotensin and preproenkephalin A mRNAs in the ipsilateral neostriatum. For proneurotensin mRNA, this increase was reflected by a substantial increase in the number of mRNA-containing cells detected. Proneurotensin mRNA-containing cells detected in the nucleus accumbens appeared to be unaffected by the intrastriatal pertussis toxin microinjection. In contrast, the significant increase in preproenkephalin A mRNA, when compared to the contralateral uninjected striatum and the ipsilateral striatum of control sham injected rats, was reflected by an increase in the cellular amount of preproenkephalin A mRNA and not by an increase in the number of mRNA-containing cells detected. These results demonstrate that the expression of both proneurotensin mRNA and preproenkephalin A mRNA in the adult rat striatum are rapidly increased in vivo by an intrastriatal microinjection of pertussis toxin.

Compartmental distribution of cytochrome oxidase in the striatum of the rat

Endogenous cytochrome oxidase activity was investigated in the adult rat striatum at the light microscope level to see if it was distributed in accordance with the established striatal patch/matrix compartmentalisation. Striatal sections stained to visualise cytochrome oxidase activity were compared with serial sections stained to visualise tyrosine hydroxylase and calbindinD28k-like immunoreactivity, established markers of the matrix compartment. The distribution of endogenous cytochrome oxidase activity was found to coincide with the immunocytochemical staining pattern seen for tyrosine hydroxylase and calbindinD28k whereby areas of intense tyrosine hydroxylase and calbindinD28k-like immunoreactivity (termed the matrix) corresponded to areas of intense cytochrome oxidase activity. Conversely, areas of less intense tyrosine hydroxylase and calbindinD28k-like immunoreactivity (termed patches) corresponded to areas of low cytochrome oxidase activity. In addition, the distribution of two other oxidative enzymes involved in the regulation of mitochondrial respiration, succinic dehydrogenase and NADH-diaphorase, was examined in the striatum and substantia nigra by using histochemical techniques. Both NADH-diaphorase and succinic dehydrogenase histochemistry showed an uneven pattern of neuropil staining in the striatum. In the substantia nigra a few intensely stained cell bodies were seen in the dorsal-lateral tip of the pars reticulata with both histochemical techniques. By using an anti-cytochrome oxidase antibody an abundance of immunoreactive cell bodies and processes were seen in the substantia nigra, particularly in the dorso-medial rim and dorsal tip of the pars reticulata. The substantia nigra pars lateralis contained many intensely stained cytochrome oxidase-like immunoreactive cell bodies and processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of acute dopaminergic D1 and D2 receptor antagonists on proneurotensin mRNA expression in rat striatum

The effect of acute dopamine (DA) antagonist treatment on neuronal proneurotensin (NT) mRNA was investigated in the rat striatum using a technique of non-radioactive in situ hybridisation. Adult Wistar rats were given a single intraperitoneal injection of either raclopride (D2 antagonist), SCH 23390 (D1 antagonist) or its inactive isomer SCH 23388 and left to survive for 3 h. Their brains were rapidly removed and striatal sections processed for in situ hybridisation using an alkaline phosphatase (AP) labelled oligonucleotide specific for NT mRNA. Blockade of the DA D2 receptors by a single injection of raclopride resulted in an increase in the number of NT mRNA containing cells in the dorsal lateral rim of the striatum adjacent to the corpus callosum. In contrast, no such increase was observed following blockade of the DA D1 receptors with SCH 23390. These findings demonstrate that NT mRNA expression is differentially regulated in the adult rat striatum by selective D1 and D2 antagonists.

Dopaminergic D1 and D2 receptor antagonists decrease prosomatostatin mRNA expression in rat striatum

The effect of acute dopamine receptor antagonist treatment on cellular prosomatostatin mRNA expression was investigated in the adult rat striatum using the technique of non-radioactive in situ hybridization. Adult female Wistar rats were given a single intraperitoneal injection of either raclopride (D2 antagonist), SCH 23390 (D1 antagonist) or the D1 (S) enantiomer SCH 23388. Animals were killed either 1, 3 or 9 h following the single i.p. injection and their brains rapidly removed. Striatal sections were then processed for in situ hybridization using an alkaline phosphatase-labelled oligonucleotide probe complementary to a portion of the rat somatostatin cDNA. Blockade of dopamine D1 and D2 receptors resulted in a significant decrease in the cellular content of prosomatostatin mRNA. However, no change in the number of prosomatostatin mRNA containing striatal cells was observed following any of the treatments at any time point. These findings demonstrate that the cellular content of prosomatostatin mRNA in the adult rat striatum is influenced by selective dopamine D1 and D2 receptor antagonists. Further, these findings are consistent with a functional interaction between dopamine and somatostatin in the rat striatum.

A rapid method of non radioactive Northern blot analysis

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Cellular localisation of enkephalin gene expression in MPTP-treated cynomolgus monkeys

Cellular sites of enkephalin gene expression were investigated using the technique of in situ hybridization in the normal striatum and in the denervated striatum of monkeys depleted of dopamine by pretreatment with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Animals received MPTP by either (a) intravenous injection to induce generalized parkinsonism, or (b) infusion into one carotid artery to induce unilateral parkinsonism. The animals which received systemic injections of MPTP were found to have an essentially total loss of nigral dopamine cells whereas the intracarotid MPTP treatment was found to destroy approximately 95% of the dopamine neurons in the ipsilateral substantia nigra. A double-stranded cDNA probe encoding the human preproenkephalin (PPE) gene was isotopically labelled with 35S and used to detect PPE mRNA within striatal tissue sections. Application of this radiolabelled cDNA probe to lightly fixed striatal sections from both groups of animals revealed an increase in expression of PPE mRNA within denervated striatal enkephalinergic neurons relative to control tissue. An increase in the number of detectable enkephalinergic mRNA-positive neurons relative to control tissue was also noted. These results suggest that the nigral dopaminergic neurons tonically inhibit PPE gene expression in the striatum.

Distribution and characterisation of neuromedin U-like immunoreactivity in rat brain and intestine and in guinea pig intestine

Neuromedin U-8 (NMU-8) is a peptide isolated from porcine spinal cord which contracts blood vessels and the uterus. Antisera were raised against NMU-8 and used in a radioimmunoassay (RIA) together with HPLC to characterize NMU-like immunoreactivity (NMU-LI) in tissues extracts of rat brain and gut and guinea pig gut. Samples of duodenum, ileum and distal colon were taken from both species, and processed for detection of NMU-LI by fluorescence immunohistochemistry. In RIA the antiserum had no cross-reactivity with neuropeptide Y, vasoactive intestinal peptide or the C-terminal hexapeptide of pancreatic polypeptide. Preincubation of antiserum with any of these peptides had no effect on the NMU-LI staining. In rats the highest content of NMU-LI was found in the ileum and the lowest in the cerebral cortex and striatum. HPLC studies showed that at least two molecular forms of NMU-LI were present in both species. In rat small intestine, subpopulations of submucous and myenteric neurones were stained; nerve fibres and terminals within these ganglia and in the mucosa were also seen. NMU-LI was sparse in the muscle. In guinea pig ileum small populations of nerve terminals were seen in both myenteric and submucous ganglionated plexuses. No endocrine cells were stained in either species.