Long CGG-repeat tracts are toxic to human cells: implications for carriers of Fragile X premutation alleles

People with 59-200 CGG.CCG-repeats in the 5' UTR of one of their FMR1 genes are at risk for Fragile X tremor and ataxia syndrome. Females are also at risk for premature ovarian failure. These symptoms are thought to be due to the presence of the repeats at the DNA and/or RNA level. We show here that long transcribed but untranslated CGG-repeat tracts are toxic to human cells and alter the expression of a wide variety of different genes including caspase-8, CYFIP, Neurotensin and UBE3A.

Neuropeptide neurotensin stimulates intestinal wound healing following chronic intestinal inflammation

Because neurotensin (NT) and its high-affinity receptor (NTR1) modulate immune responses, chloride secretion, and epithelial cell proliferation, we sought to investigate their role in the repair process that follows the development of mucosal injuries during a persistent inflammation. Colonic NT and NTR1, mRNA, and protein significantly increased only after dextran sodium sulfate (DSS)-induced inflammatory damage developed. Colitis-induced body weight loss, colonic myeloperoxidase activity, and histological damage were significantly enhanced by SR-48642 administration, a nonpeptide NTR1 antagonist, whereas continuous NT infusion ameliorated colitis outcome. To evaluate the NT and NTR1 role in tissue healing, mucosal inflammatory injury was established administering 3% DSS for 5 days. After DSS discontinuation, mice rapidly gained weight, ulcers were healed, and colonic NT, NTR1, and cyclooxygenase (COX)-2 mRNA levels were upregulated, whereas SR-48642 treatment caused a further body weight loss, ulcer enlargement, and a blunted colonic COX-2 mRNA upregulation. In a wound-healing model in vitro, NT-induced cell migration in the denuded area was inhibited by indomethacin but not by an antitransforming growth factor-beta neutralizing antibody. Furthermore, NT significantly increased COX-2 mRNA levels by 2.4-fold and stimulated PGE(2) release in HT-29 cells. These findings suggest that NT and NTR1 are part of the network activated after mucosal injuries and that NT stimulates epithelial restitution at least, in part, through a COX-2 dependent pathway.

Endogenous neurotensin attenuates dopamine-dependent locomotion and stereotypy

The neuropeptide neurotensin (NT) is highly sensitive to changes in dopaminergic signaling in the striatum, and is thought to modulate dopamine-mediated behaviors. To explore the interaction of NT with the dopamine system, we utilized mice with a targeted deletion of dopamine synthesis specifically in dopaminergic neurons. Dopamine levels in dopamine-deficient (DD) mice are less than 1% of control mice, and they require daily administration of the dopamine precursor L-dihydroxyphenylalanine (L-DOPA) for survival. DD mice are supersensitive to the effects of dopamine, becoming hyperactive relative to control mice in the presence of L-DOPA. We show that 24 h after L-DOPA treatment, when DD mice are in a "dopamine-depleted" state, Nt mRNA levels in the striatum of DD mice are similar to those in control mice. Administration of L-DOPA or L-DOPA plus the L-amino acid decarboxylase inhibitor, carbidopa, (C/L-DOPA) induced Nt expression in the striatum of DD mice. The dopamine D1 receptor antagonist, SCH23390, blocked C/L-DOPA-induced Nt. To test the hypothesis that this striatal Nt expression modulated dopamine-mediated behavior in DD mice, we administered SR 48692, an antagonist of the high affinity NT receptor, together with L-DOPA or C/L-DOPA. L-DOPA-induced hyperlocomotion and C/L-DOPA-induced stereotypy were potentiated by peripheral administration of SR 48692. Furthermore, intrastriatal microinjections of SR 48692 augmented L-DOPA-induced hyperlocomotion. These results demonstrate a dynamic regulation of striatal Nt expression by dopamine via D1 receptors in DD mice, and point to a physiological role for endogenous striatal NT in counteracting motor behaviors induced by an overactive dopamine system.

Species differences in brain pre-pro-neurotensin/neuromedin N mRNA distribution: the expression pattern in mice resembles more closely that of primates than rats

We have used in situ hybridization to determine the distribution of pre-pro-neurotensin/neuromedin N (NT/N) mRNA in the brain of mice and rats. In rats and mice, expression was observed in the lateral septal nucleus, nucleus accumbens, medial preoptic area, bed nucleus of the stria terminalis, lateral hypothalamus, central amygdaloid nucleus and the subicilum. However, several differences in the NT/N mRNA distribution were observed between rats and mice in other brain areas. In mice, NT/N expression was detected in the subthalamic nucleus and geniculate nucleus, whereas expression was not observed in these brain areas in rats. Surprisingly, expression was not observed in mouse mesencephalic dopaminergic (mesDA) neurons and the CA1 area of the hippocampus, areas known to contain NT/N mRNA in the rat brain. Taken together, these results show that although the brain NT/N mRNA distribution largely overlaps in mice and rats, species differences exist in specific brain areas in rodents. Moreover, these data indicate that the distribution in mice resembles most that of primates than rats.

Developmental expression of neurotensin in thyrotropes and gonadotropes of male and female rats

Besides its potential roles as a central neuromodulator or a hypothalamic neurohormone, neurotensin (NT) may also have endocrine function in the anterior pituitary of mammals. We previously found that NT immunoreactivity is present in the secretory granules of gonadotropes and thyrotropes in both male and female rats, where its levels of expression are under the control of sex steroids. In this work, using immunocytochemistry and in situ hybridization, we have studied the postnatal development of NT-like immunoreactivity (NTir) and the mRNA encoding NT (mRNA-NT) in specific anterior pituitary cells of both male and female rats. NT expression starts after birth and displays an identical pattern in both sexes until sexual maturity, with mRNA-NT being detected from day 2 of postnatal life in thyrotropes localized in the central portion of the anterior lobe. This pattern of expression develops progressively throughout the 2nd and 3rd weeks in both sexes. By the beginning of the 3rd week, mRNA-NT can also be detected in gonadotropes localized in the periphery of the gland coinciding with a rise in serum estradiol concentrations in both sexes, and by day 21, mRNA-NT is extensively present in both the periphery and the central region. NTir is observed from days 5-6 in thyrotropes predominantly localized in the central portion of the anterior lobe, and by day 21, NTir is also detected in gonadotropes localized in the periphery of the gland. This pattern remains similar in both sexes until the time of puberty, when female rats start displaying plastic changes in NT expression according to the stage of the estrous cycle. These findings indicate that NT expression in the rat anterior pituitary is cell specific, and develops from birth to adulthood under the control of sex steroid hormones. In addition, preliminary data showing the presence of NT receptors in rat pituitary cells support the hypothesis of a paracrine or an autocrine role for this peptide within the pituitary.

Development of the human motor-related thalamic nuclei during the first half of gestation, with special emphasis on GABAergic circuits

This study analyzed the expression of differentiation markers (Calbindin D28K: CaBP; parvalbumin: PARV; calretinin: CalR), gamma-aminobutyric acid (GABA) markers (GABA, glutamic acid decarboxylases: GAD65, GAD67; and GABA transporters: GAT1, GAT3), and other markers (neurotensin: NT, and neurofilament-specific protein: SMI32) in the human thalamus at 8-23 gestation weeks (g.w.), focusing on the motor-related nuclei. From 8-13 g.w. mainly CaBP was expressed in the cells while fiber bundles traversing the thalamus in addition to CaBP expressed all GABA markers except GAD67. CaBP and PARV expression patterns in different nuclei changed over the time course studied, whereas NT was expressed consistently along the anterior-lateral curvature of the thalamus. CalR and SMI were detectable at 23 g.w. in the ventral parts of the dorsal thalamus. Most remarkably, punctate GAD65 immunoreactivity in the neuropil was confined to the nigro- and pallidothalamic afferent receiving nuclei from 16 to about 21 g.w., overlapping with that of CaBP in some of these nuclei (subdivisions of the ventral anterior and mediodorsal nuclei) and with PARV in others (centromedian nucleus). During this period, GAD65 immunoreactivity can be considered a marker of the basal ganglia afferent receiving territory in the motor thalamus. GAD67-positive local circuit neurons were first detected at 12-13 g.w. in the thalamic nuclei outside the basal ganglia afferent receiving territory. In the ventral anterior and centromedian nuclei, GAD-containing local circuit neurons were not conspicuous even at 22-23 g.w. The cells of the reticular nucleus expressed GAD67 and PARV from 12 g.w. on starting in the lateral-posterior regions. By 23 g.w., both markers were expressed in about two-thirds of the nucleus except for its most medial-anterior part. The results imply spatially and temporally differential expression of GABA and differentiation markers in the developing human thalamus.

Altered neurotensin mrna expression in mice lacking the dopamine transporter

Psychostimulants and antipsychotic drugs increase mRNA expression of the neuropeptide neurotensin (NT) in the striatum and nucleus accumbens. In the present study, we used mice lacking the dopamine transporter (DAT) to investigate the consequences of a chronic hyperdopaminergic state on NT gene expression. NT mRNA expression was examined under basal conditions and after administration of haloperidol or amphetamine using in situ hybridization with a digoxigenin-labeled NT cRNA probe. DAT-/- mice exhibited a striking increase in the number of NT mRNA-expressing perikarya in the substantia nigra and ventral tegmental area, as well as a less pronounced increase in the lateral septum compared with wild-type littermates. No changes were detected in other regions expressing NT mRNA. Acute administration of haloperidol (1 mg/kg) induced a significant increase in the number of NT mRNA-expressing neurons in the dorsomedial and dorsolateral striatum of wild-type mice but failed to stimulate NT gene expression in DAT mutants. In contrast, a higher dose of haloperidol (5 mg/kg) stimulated striatal NT mRNA expression both in DAT+/+ and DAT-/- mice. Amphetamine (10 mg/kg) increased the number of hybridized neurons in the nucleus accumbens shell and fundus striati of wild-type and DAT-/- mice, indicating that the drug acted through a target other than DAT, such as the serotonin or the norepinephrine transporters. The up-regulation of NT mRNA observed in DAT-/- mice may represent an adaptive mechanism in response to constitutive hyperdopaminergia. These results illustrate the profound alterations in the NT system induced by chronic stimulation of DA receptors and underscore the potential clinical relevance of NT/DA interactions in schizophrenia and drug abuse.

Conserved SNH domain of the proto-oncoprotein SYT interacts with components of the human chromatin remodelling complexes, while the QPGY repeat domain forms homo-oligomers

Many studies have now established that the SWI/SNF chromatin remodelling complexes are involved in activation and repression of a variety of genes. In mammalian cells, these complexes contain the BRM and BRG1 helicase-like proteins that are thought to be responsible for nucleosome remodelling. The proto-oncoprotein SYT, involved in the unique translocation t(X;18) found in synovial sarcoma, is known to interact with human BRM (hBRM), thus providing a link between chromatin remodelling factors and human cancer. In this work, we address how SYT interacts with hBRM and BRG1. We demonstrate that the conserved N-terminal SNH domain of SYT, which is also present in the oncoproteins SYT-SSX, binds to both hBRM and BRG1. We have also found that in vivo the C-terminus transactivation QPGY region of SYT can interact with itself. This results in an amplified interaction with hBRM and highlights a possible regulatory function of this domain in cells.

Mutational analysis of neurotensin in familial restless legs syndrome

A susceptibility locus for restless legs syndrome (RLS) has been identified recently on chromosome 12q. This region contains several transcribed genes including neurotensin (NTS), which, as an important modulator of the dopaminergic transmission, represents a strong functional and positional candidate in the context of RLS. In this study, NTS was evaluated for mutational analysis. A panel of 19 individuals from 4 families supporting linkage to 12q was investigated using a combined denaturing high-performance liquid chromatography (dHPLC) and direct sequencing method. Analysis of the NTS genomic sequence revealed 2 intronic polymorphisms and 1 variant located in the 5' untranslated region (UTR). None of the observed variants co-segregated with RLS and no disease-associated polymorphisms were detected in any of the analyzed families. Based on these results, it is unlikely that NTS is the gene responsible for RLS in chromosome 12-linked families.

The conformation of neurotensin bound to its G protein-coupled receptor

G protein-coupled receptors (GPCRs) mediate the perception of smell, light, taste, and pain. They are involved in signal recognition and cell communication and are some of the most important targets for drug development. Because currently no direct structural information on high-affinity ligands bound to GPCRs is available, rational drug design is limited to computational prediction combined with mutagenesis experiments. Here, we present the conformation of a high-affinity peptide agonist (neurotensin, NT) bound to its GPCR NTS-1, determined by direct structural methods. Functional receptors were expressed in Escherichia coli, purified in milligram amounts by using optimized procedures, and subsequently reconstituted into lipid vesicles. Solid-state NMR experiments were tailored to allow for the unequivocal detection of microgram quantities of 13C,15N-labeled NT(8-13) in complex with functional NTS-1. The NMR data are consistent with a disordered state of the ligand in the absence of receptor. Upon receptor binding, the peptide undergoes a linear rearrangement, adopting a beta-strand conformation. Our results provide a viable structural template for further pharmacological investigations.

Neurotensin: dual roles in psychostimulant and antipsychotic drug responses

Central administration of neurotensin (NT) results in a variety of neurobehavioral effects which, depending upon the administration site, resemble the effects of antipsychotic drugs (APDs) and psychostimulants. All clinically effective APDs exhibit significant affinities for dopamine D(2) receptors, supporting the hypothesis that an increase in dopaminergic tone contributes to schizophrenic symptoms. Psychostimulants increase extracellular dopamine (DA) levels and chronics administration can produce psychotic symptoms over time. APDs and psychostimulants induce Fos and NT expression in distinct striatal subregions, suggesting that changes in gene expression underlie some of their effects. To gain insight into the functions of NT, we analyzed APD and psychostimulant induction of Fos in NT knockout mice and rats pretreated with the NT antagonist SR 48692. In both NT knockout mice and rats pretreated with SR 48692, haloperidol-induced Fos expression was markedly attenuated in the dorsolateral striatum; amphetamine-induced Fos expression was reduced in the medial striatum. These results indicate that NT is required for the activation of specific subpopulations of striatal neurons in distinct striatal subregions in response to both APDs and psychostimulants. This review integrates these new findings with previous evidence implicating NT in both APD and psychostimulant responses.

Effect of ileocolonic transposition on gut morphology, gene expression, and function

Intestinal morphology and expression of brush border enzymes can be dramatically altered by nutrient composition and position along the longitudinal gut axis. In contrast, endocrine gene expression appears to be relatively "imprinted" and is not significantly altered by positional changes. The purpose of our study was to assess the effects of transposing the ileum into the colonic position on intestinal morphology, gene expression, and enzyme activity. For this study, male Sprague-Dawley rats underwent either transposition of an approximately 8-cm segment of distal ileum into the colonic position or sham operation. Rats were sacrificed 2 months after operation and transposed or sham ileum was assessed. We found that transposition of the ileum to the colonic position resulted in no change in the ileal mucosal architecture. Furthermore, no change in the expression of the endocrine genes neurotensin and PYY or the apoptotic genes was detected. Although sucrase-isomaltase activity was decreased in the transposed ileum, this decrease did not achieve statistical significance. These results demonstrate that the ileum can be successfully interposed into the colonic position. In this location, the ileum functions normally without changes in the villus morphology or gene expression pattern despite the change in position and composition of the luminal content.

Acute and chronic administration of melanin-concentrating hormone enhances food intake and body weight in Wistar and Sprague-Dawley rats

AIM

Although melanin-concentrating hormone (MCH) is believed to be an important regulator of feeding behavior, both its acute and chronic effects on food intake as well as its interaction with other brain peptides involved in the control of appetite remain unclear. Therefore, the acute effects of MCH on food intake and the chronic effect of MCH on food intake and the gene expression of various hypothalamic peptides involved in the control of appetite were studied in rats.

METHODS AND RESULTS

Either the acute or the continuous intraventricular infusion of MCH for 12 days stimulated feeding in both Wistar or Sprague-Dawley rats. Removal of the hypothalamus at the end of the chronic infusion studies allowed measurement of the expression of mRNAs encoding for MCH, neuropeptide Y (NPY), orexin, agouti gene-related peptide, cocaine and amphetamine-related transcript and neurotensin-neuropeptides involved in the control of appetite. Chronic intraventricular infusion of MCH activated only NPY mRNA synthesis in Sprague-Dawley rats. The increase in food intake in response to MCH in Sprague-Dawley rats did not appear to be due to the release of NPY since combination studies demonstrated consistently additive effects of the two peptides on food intake at maximum or near maximum doses.

CONCLUSIONS

These results strongly suggest that MCH is an orexigenic peptide involved in the control of both short- and long term food intake in satiated rats and further indicate that the MCH pathway is a possible target for the control of food intake and obesity.

Improved neurotensin-vector-mediated gene transfer by the coupling of hemagglutinin HA2 fusogenic peptide and Vp1 SV40 nuclear localization signal

Recently we reported that neurotensin-SPDP-poly-L-lysine (NT-vector) is able to bind plasmid DNA (NT-polyplex) and polyfect cells expressing the high-affinity neurotensin receptor (NTRH) although with low transfecting efficiency: in vitro, 6.5+/-1.5%, and in vivo, 5+/-4%. In this work, we attempted to increase the transfecting efficiency by integrating the hemagglutinin HA2 fusogenic peptide and the Vp1 nuclear localization signal of SV40 to the NT-polyplex (fusogenic-karyophilic-NT-polyplex). Confocal microscopy and flow cytometry analysis showed that the fusogenic-karyophilic-NT-polyplex produced mostly nuclear localization of the plasmid DNA in NTRH-bearing N1E-115 cells. About 50% of N1E-115 cells internalized and expressed the reporter gene when the plasmid DNA was transferred by the fusogenic-karyophilic-NT-polyplex. Although to a less extent, the addition of each viral peptide separately to NT-polyplex (fusogenic-NT-polyplex or karyophilic-NT-polyplex) improved polyfection. Fusogenic-NT-polyplex produced 22.41+/-5.96% of internalization and 20.35+/-0.82% of expression in N1E-115 cells, whereas karyophilic-NT-polyplex yielded 13.75+/-3.88% and 10.94+/-2.04%, respectively. Basal internalization and expression were detected in N1E-115 cells in the presence of 100 nM SR-48692 and in NTRH-lacking cells. The fusogenic-karyophilic-NT-polyplex was microinjected into the substantia nigra to test its ability for gene transfer in vivo. Fusogenic-karyophilic-NT-polyplex internalization was observed within dopamine neurons only. Reporter gene expression was observed in a high proportion of dopamine neurons up to 60 days after NT-polyfection. Both internalization and expression were prevented by SR-48692. Our results show that the fusogenic-karyophilic-NT-polyplex is a highly efficient and specific gene vector and encourage its use to transfer gene of physiological interest to NTRH-bearing neurons.

Endocrine gene neurotensin: molecular mechanisms and a model of intestinal differentiation

The peptide neurotensin (NT) is an important intestinal hormone that affects gastrointestinal (GI) secretion, motility, and growth. This review describes the effects of NT in the GI tract and the distribution and localization of the gene encoding NT (i.e., NT/N). In addition, the molecular regulation of NT/N gene expression is discussed with special emphasis on the transcription factors, signal transduction pathways, and the role of gene methylation in modulating NT/N gene expression. Our studies have identified the NT/N gene as an excellent molecular model by which to define factors regulating intestinal cell differentiation. The in-depth analysis of the cellular processes leading to the expression of "model" intestinal genes, such as NT/N, can provide better understanding of normal gut development and function as well as defining more clearly the cellular events leading to gut neoplasia.

Modulation of neuroleptic activity of 9,10-didehydro-N-methyl-(2-propynyl)-6-methyl-8-aminomethylergoline bimaleinate (LEK-8829) by D1 intrinsic activity in hemi-parkinsonian rats

Parkinsonism, a common unwanted side effect of typical antipsychotic (neuroleptic) drugs, is induced by the blockade of striatal dopamine D2 receptors. In rats with hemi-parkinsonism induced by unilateral lesion of dopaminergic nigrostriatal neurons with 6-hydroxydopamine, D2 antagonists inhibit contralateral turning induced by D2 agonists and augment the levels of neurotensin mRNA in dopaminergically intact striatum. By contrast, D1 agonists induce contralateral turning and augment neurotensin mRNA levels in dopamine-depleted striatum. These effects could be inhibited by D1 but not by D2 antagonists. Here we used a hemi-parkinsonian model to investigate the effects of putative D1 agonist/D2 antagonist LEK-8829 (9,10-didehydro-N-methyl-(2-propynyl)-6-methyl-8-aminomethylergoline bimaleinate), an experimental antipsychotic, on turning behavior and the expression of striatal neurotensin, preprotachykinin and neurotransmitter-induced early gene protein 4 (ania-4) mRNAs. We found that LEK-8829 inhibited contralateral turning induced by D2 agonist quinpirole, but only if the rats were cotreated with D1 antagonist SCH-23390. In situ hybridization showed that LEK-8829 induced the expression of neurotensin and ania-4 mRNAs in dopamine-intact striatum that could be completely blocked only by the combined treatment with SCH-23390 and quinpirole. In addition, LEK-8829 augmented the expression of neurotensin, preprotachykinin and ania-4 mRNAs in dopamine-depleted striatum that could be completely blocked by SCH-23390. This study clearly demonstrates that in hemi-parkinsonian rats D1 agonistic activity of LEK-8829 confers its anti-parkinsonian drug-like properties and modulates its neuroleptic drug-like properties, which are dependent on the blockade of dopamine D2 receptors. These findings imply that atypical antipsychotics with D1 intrinsic activity might have a reduced propensity for the induction of extrapyramidal syndrome.

Production of recombinant large proneurotensin/neuromedin N-derived peptides and characterization of their binding and biological activity

Proneurotensin/neuromedin N (pro-NT/NN) is the common precursor of two biologically active related peptides, neuromedin N (NN) and neurotensin (NT). It undergoes a tissue-specific processing leading to the formation in some tissues and cancer cell lines of large peptides ending with the NT (large NT) or NN (large NN) sequence. In this study, we prepared and purified high amounts of recombinant large NT and large NN using the Drosophila S2 cell expression system. The binding and pharmacological properties of recombinant large peptides were characterized and compared to those of NT and NN using either COS cells transfected with the human subtype-1 NT receptor (hNTS1) or the human colon adenocarcinoma HT29 cell line that endogenously expresses hNTS1. Furthermore, the metabolic stability of the large peptides, when exposed to HT29 cells, was compared to that of NT and NN. Both large NT and large NN were able to bind to and activate hNTS1 with potencies that were approximately 10 times lower than that of their small counterpart. In addition, the large forms proved to be far less sensitive to degradation than the small peptides. Taken together, these data suggest that the large forms might represent endogenous, long-lasting activators of hNTS1 in a number of physiopathological situations.

The role of neurotensin in the pathophysiology of schizophrenia and the mechanism of action of antipsychotic drugs

It has become increasingly clear that schizophrenia does not result from the dysfunction of a single neurotransmitter system, but rather pathologic alterations of several interacting systems. Targeting of neuropeptide neuromodulator systems, capable of concomitantly regulating several transmitter systems, represents a promising approach for the development of increasingly effective and side effect-free antipsychotic drugs. Neurotensin (NT) is a neuropeptide implicated in the pathophysiology of schizophrenia that specifically modulates neurotransmitter systems previously demonstrated to be dysregulated in this disorder. Clinical studies in which cerebrospinal fluid (CSF) NT concentrations have been measured revealed a subset of schizophrenic patients with decreased CSF NT concentrations that are restored by effective antipsychotic drug treatment. Considerable evidence also exists concordant with the involvement of NT systems in the mechanism of action of antipsychotic drugs. The behavioral and biochemical effects of centrally administered NT remarkably resemble those of systemically administered antipsychotic drugs, and antipsychotic drugs increase NT neurotransmission. This concatenation of findings led to the hypothesis that NT functions as an endogenous antipsychotic. Moreover, typical and atypical antipsychotic drugs differentially alter NT neurotransmission in nigrostriatal and mesolimbic dopamine (DA) terminal regions, and these effects are predictive of side effect liability and efficacy, respectively. This review summarizes the evidence in support of a role for the NT system in both the pathophysiology of schizophrenia and the mechanism of action of antipsychotic drugs.

Neurons of origin of the neurotensinergic plexus enmeshing the ventral tegmental area in rat: retrograde labeling and in situ hybridization combined

The morphological and physiological substrates that underlie the mutual regulatory interactions of neurotensin and dopamine in the rat mesotelencephalic projections and related structures remain to be fully described. A salient candidate for neurotensinergic effects on the mesotelencephalic dopamine projection is the dense plexus of neurotensin immunoreactive axons that enmeshes the ventral tegmental area and substantia nigra, but the locations of the neurons that give rise to this plexus have not been identified and its systemic context remains obscure. To address this, Fluoro-Gold and the cholera toxin beta subunit, retrogradely transported axonal tracers, were injected into the ventral tegmental area of rats and the brains were processed to demonstrate neurons that contained both retrograde tracer immunoreactivity and a probe against neurotensin/neuromedin N messenger RNA. Substantial numbers of double-labeled neurons were observed in the rostral part of the lateral septum, and in a region centered on the shared boundaries of the bed nucleus of stria terminalis, ventromedial ventral pallidum, diagonal band of Broca, lateral preoptic area and rostral lateral hypothalamus. A few double-labeled neurons were also observed in the dorsal raphe nucleus and adjacent periaqueductal gray. Despite the administration of haloperidol and D-amphetamine to elicit and enhance neurotensin/neuromedin N messenger RNA expression in striatum, including the nucleus accumbens and olfactory tubercle, no double-labeled neurons were observed there. These results identify a novel brain substrate for control of midbrain dopamine levels, which affect reward mechanisms and motivation.

The endocrine disrupters butyl benzyl phthalate and bisphenol A increase the expression of progesterone receptor messenger ribonucleic acid in the preoptic area of adult ovariectomized rats

Butyl benzyl phthalate (BBP) and bisphenol A (BPA), so-called endocrine disrupters, are known to mimic the action of estrogens: they are thus liable to influence reproductive functions. Since little is known about their action on gene expression in the adult hypothalamus, we examined the effects of these chemicals on the expression of estrogen-regulated mRNAs, i.e., progesterone receptor (PR) mRNA, preproenkephalin (PPE) mRNA and neurotensin (NT) mRNA, in the hypothalamus and pituitary of adult female rats. Two weeks after ovariectomy, rats were subcutaneously injected with 10 mg BBP, 10 mg BPA, or 10 microg 17 beta-estradiol (E(2)) in sesame oil, or with sesame oil alone as a control. Twenty-four hours after the injection, tissues including the preoptic area (POA), mediobasal hypothalamus (MBH) and anterior pituitary were collected. Northern blot revealed that injection of E(2) resulted in expected changes, i.e., significant increases in PR mRNA in the POA, MBH and anterior pituitary, and in PPE mRNA in the MBH. We also found that injection of BPA significantly increased PR mRNA in the POA and anterior pituitary, while injection of BBP increased PR mRNA in the POA and anterior pituitary, although the increase in the anterior pituitary was not significant. No significant effect of E(2), BPA, or BBP on NT mRNA in the POA was detected. The present study demonstrates that the two endocrine disrupters BPA and BBP can increase the expression of PR mRNA in the POA of adult ovariectomized rats.

Neurotensin gene expression increases during proestrus in the rostral medial preoptic nucleus: potential for direct communication with gonadotropin-releasing hormone neurons

Neurotensin (NT)-containing neurons in the rostral portion of the medial preoptic nucleus (rMPN) of the brain may play a key role in regulating the pattern of secretion of GnRH, thereby influencing the reproductive cycle in females. The major goals of this study were to determine whether NT messenger RNA (mRNA) levels in the rMPN exhibit a unique pattern of expression in temporal association with the preovulatory LH surge and to assess whether NT neurons may communicate directly with GnRH neurons. We analyzed NT gene expression in rats using in situ hybridization over the day of proestrus and compared this with diestrous day 1. We also determined whether the high-affinity NT receptor (NT1) is expressed in GnRH neurons using dual-label in situ hybridization and whether this expression varies over the estrous cycle. We found that NT mRNA levels in the rMPN increase significantly on the day of proestrus, rising before the LH surge. No such change was detected on diestrous day 1, when the LH surge does not occur. Furthermore, we observed that a significant number of GnRH neurons coexpress NT1 mRNA and that the number of GnRH neurons expressing NT1 mRNA peaks on proestrus. Together with previous findings, our results suggest that increased expression of NT in the rMPN may directly stimulate GnRH neurons on proestrus, contributing to the LH surge. In addition, our results suggest that responsiveness of GnRH neurons to NT stimulation is enhanced on proestrus due to increased expression of NT receptors within GnRH neurons.

Differential effects of cocaine and methamphetamine on neurotensin/neuromedin N and preprotachykinin messenger RNA expression in unique regions of the striatum

This study employed in situ hybridization to directly compare the effects of cocaine and methamphetamine on neurotensin/neuromedin N and preprotachykinin messenger RNAs in distinct striatal regions. Male, Sprague-Dawley rats received a single administration of 15mg/kg methamphetamine (s.c.) or 30mg/kg cocaine (i.p.) and were killed 30min or 3h later. Methamphetamine and cocaine produced significant increases in preprotachykinin messenger RNA in the striatum after 3h, but often in different subregions. Both drugs produced similar effects on preprotachykinin messenger RNA in the rostral striatum. However, methamphetamine produced significant increases in all regions of the caudal striatum, whereas cocaine-induced preprotachykinin messenger RNA expression was limited to dorsal regions of this striatal area. Methamphetamine also produced a significant increase in preprotachykinin messenger RNA in the caudal striatum after 30min, whereas cocaine had no significant effect on preprotachykinin messenger RNA at this early time-point. The pattern of changes in neurotensin/neuromedin N messenger RNA caused by methamphetamine and cocaine after 3h was even more distinct. Cocaine produced significant increases in neurotensin/neuromedin N messenger RNA in all regions of the rostral striatum, whereas methamphetamine had no effect in these areas. Furthermore, in more caudal sections, cocaine predominantly affected neurotensin/neuromedin N expression in dorsal aspects of the striatum, whereas methamphetamine significantly increased neurotensin/neuromedin N messenger RNA in all regions. There was much less effect of either drug on neuropeptide expression in the nucleus accumbens. The only significant effect was an increase in neurotensin/neuromedin N messenger RNA in the core region 3h after methamphetamine administration. These results indicate that methamphetamine and cocaine increase preprotachykinin and neurotensin/neuromedin N messenger RNAs in distinct regions of the striatum. The ability of methamphetamine and cocaine to alter neuropeptide messenger RNA expression in unique regions of the striatum may be important for the long-term effects of these drugs, such as sensitization, since the striatum is not homogeneous in its connections and function.

Neurotensin gene expression and behavioral responses following administration of psychostimulants and antipsychotic drugs in dopamine D(3) receptor deficient mice

Exposure to psychostimulants and antipsychotics increases neurotensin (NT) gene expression in the striatum and nucleus accumbens. To investigate the contribution of D(3) receptors to these effects we used mice with targeted disruption of the D(3) receptor gene. Basal NT mRNA expression was similar in D(3) receptor mutant mice and wild-type animals. Acute administration of haloperidol increased NT gene expression in the striatum in D(3)+/+, D(3)+/- and D(3)-/- mice. Similarly, acute cocaine and amphetamine induced NT mRNA expression in the nucleus accumbens shell and olfactory tubercle to a comparable extent in D(3) mutants and wild-type mice. Daily injection of cocaine for seven days increased NT mRNA in a restricted population of neurons in the dorsomedial caudal striatum of D(3)+/+ mice, but not in D(3)-/- and D(3)+/- animals. No differences were observed between D(3) receptor mutant mice and wild-type littermates in the locomotor activity and stereotyped behaviors induced by repeated cocaine administration. These findings demonstrate that dopamine D(3) receptors are not necessary for the acute NT mRNA response to drugs of abuse and antipsychotics but appear to play a role in the regulation of NT gene induction in striatal neurons after repeated cocaine. In addition, our results indicate that the acute locomotor response to cocaine and development of psychostimulant-induced behavioral sensitization do not require functional D(3) receptors.

Cold water swim stress increases the expression of neurotensin mRNA in the lateral hypothalamus and medial preoptic regions of the rat brain

Stress-induced analgesia is a well-documented phenomenon that occurs in all mammalian species. Forced cold water swim produces a type of stress-induced analgesia that is independent of mu opioid receptors. The neuropeptide neurotensin (NT) has been implicated in mu opioid-independent analgesia (MOIA), but the circuitry of this system is largely unknown. The medial preoptic area (MPO) and lateral hypothalamus (LH) are two regions that are known to modulate pain processing. These two regions also contain neurotensinergic projections to the periaqueductal gray, a region that has been shown to produce MOIA upon injection of NT. The goal of this study was to determine if cold water swim (CWS) stress, which produces MOIA, activates the NT-ergic systems in these two regions. In situ hybridization results indicate that CWS increases the level of NT mRNA within neurons in the MPO and LH, suggesting that these two regions are activated during this process.

Enhanced neurotensin neurotransmission is involved in the clinically relevant behavioral effects of antipsychotic drugs: evidence from animal models of sensorimotor gating

To date, none of the available antipsychotic drugs are curative, all have significant side-effect potential, and a receptor-binding profile predictive of superior therapeutic ability has not been determined. It has become increasingly clear that schizophrenia does not result from the dysfunction of a single neurotransmitter system, but rather from an imbalance between several interacting systems. Targeting neuropeptide neuromodulator systems that concertedly regulate all affected neurotransmitter systems could be a promising novel therapeutic approach for schizophrenia. A considerable database is concordant with the hypothesis that antipsychotic drugs act, at least in part, by increasing the synthesis and release of the neuropeptide neurotensin (NT). In this report, we demonstrate that NT neurotransmission is critically involved in the behavioral effects of antipsychotic drugs in two models of antipsychotic drug activity: disrupted prepulse inhibition of the acoustic startle response (PPI) and the latent inhibition (LI) paradigm. Blockade of NT neurotransmission using the NT receptor antagonist 2-[[5-(2,6-dimethoxyphenyl)-1-(4-(N-(3-dimethylaminopropyl)-N-methylcarbamoyl)-2-isopropylphenyl)-1H- pyrazole-3-carbonyl]-amino]-adamantane-2-carboxylic acid, hydrochloride (SR 142948A) prevented the normal acquisition of LI and haloperidol-induced enhancement of LI. In addition, SR 142948A blocked the PPI-restoring effects of haloperidol and the atypical antipsychotic drug quetiapine in isolation-reared animals deficient in PPI. We also provide evidence of deficient NT neurotransmission as well as a left-shifted antipsychotic drug dose-response curve in isolation-reared rats. These novel findings, together with previous observations, suggest that neurotensin receptor agonists may represent a novel class of antipsychotic drugs.