Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Lateral Line System”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,243 records · Page 69Linked to original sources
PubMed1998

Vasopressin-induced currents in rat neonatal spinal lateral horn neurons are G-protein mediated and involve two conductances.

Arginine vasopressin (AVP) receptors are expressed early in the developing spinal cord. To characterize AVP-induced conductances in lower thoracic sympathetic preganglionic (SPN) and other lateral horn neurons, we used patch-clamp recording techniques in neonatal (11-21 days) rat spinal cord slices. Most (90%) of 273 neurons, including all 68 SPNs, responded to AVP with membrane depolarization and/or a V1 receptor-mediated, dose-dependent (0.01-1.0 microM) and tetrodotoxin (TTX)-resistant inward current. A role for G-proteins was indicated by persistence of this inward current after intracellular dialysis with GTP-gamma-S or GMP-PNP, its marked reduction with GDP-beta-S, and significant reduction, but not abolition, after preincubation with pertussis toxin or in the presence of N-ethylmaleimide. Analysis of individual current-voltage (I-V) relationships in 57 cells indicated the presence of two different membrane conductances. In 21 cells, net AVP-induced currents reversed around -103 mV, reflecting reduction in one or more barium-sensitive potassium conductances; in 12 cells, net AVP-induced current reversed around -40 mV and was not significantly sensitive to several potassium channel blockers including barium, tetraethylammonium chloride (TEA), 4-aminopyridine (4AP), cesium, or glibenclamide, suggesting increase in a nonselective cationic conductance that was separate from Ih; in 24 cells where I-V lines shifted in parallel, AVP-induced inward currents were significantly greater and probably involved both conductances. These data indicate that SPNs and a majority of unidentified neonatal lateral horn neurons possess functional G-protein-coupled V1-type vasopressin receptors. The wide distribution of AVP receptors in neonatal spinal lateral column cells suggests a role that may extend beyond involvement in regulation of autonomic nervous system function.

Animals↗
PubMed2002

Dynamics of electrosensory feedback: short-term plasticity and inhibition in a parallel fiber pathway.

The dynamics of neuronal feedback pathways are generally not well understood. This is due to the complexity arising from the combined dynamics of closed-loop feedback systems and the synaptic plasticity of feedback connections. Here, we investigate the short-term synaptic dynamics underlying the parallel fiber feedback pathway to a primary electrosensory nucleus in the weakly electric fish, Apteronotus leptorhynchus. In open-loop conditions, the dynamics of this pathway arise from a monosynaptic excitatory connection and a disynaptic (feed-forward) inhibitory connection to pyramidal neurons in the electrosensory lateral line lobe (ELL). In a brain slice preparation of the ELL, we characterized the synaptic responses of pyramidal neurons to short trains of electrical stimuli delivered to the parallel fibers of the dorsal molecular layer. Stimulus trains consisted of 20 pulses, at either random intervals or constant intervals, with varying mean frequencies. With random trains, pyramidal neuron responses were well described by a single exponential function of the inter-stimulus interval-suggesting a single facilitation-like process underlies these synaptic dynamics. However, responses to periodic (constant interval) trains deviated from this simple description. Random and periodic stimulus trains delivered when the feed-forward inhibitory component of this pathway was pharmacologically blocked revealed that inhibition and depression also contribute to the observed dynamics. We formulated a simple model of the parallel fiber synaptic dynamics that provided an accurate description of our data. The model dynamics resulted from a combination of three distinct processes. Two of the processes are the classically-described synaptic facilitation and depression, and the third is a novel description of feed-forward inhibition. An analysis of this model suggests that synaptic pathways combining plasticity with feed-forward inhibition can be easily tuned to signal different types of transient stimuli and thus lead to diverse and nonintuitive filtering properties.

Animals↗
PubMed1994

Catecholamines modulate chicken immunoglobulin M and immunoglobulin G plaque-forming cells.

Norepinephrine (NE) and epinephrine (E) function as chemical messengers in the central nervous and the endocrine systems of the chicken. The effects of in vivo and in vitro exposure of NE and E on IgM and IgG splenic plaque-forming cell (pfc) formation were determined to the antigen SRBC. Six-week-old Line UNH 105 New Hampshire chickens were injected i.v. with NE (500 micrograms/kg BW) or E (100 micrograms/kg BW) followed by 1 mL of 5% SRBC 30 min later. Five days after antigen injection, IgM and IgG pfc were assayed. Compared with controls, in vivo NE suppressed (P < .05) IgM and IgG pfc formation. In vitro NE treatment of splenic lymphocytes reduced (P < .05) IgM pfc but did not affect IgG pfc numbers. In vivo treatment with E increased (P < .05) IgM pfc whereas in vitro E exposure increased (P < .05) IgM pfc. Immunoglobulin G pfc were suppressed (P < .05) by both in vivo and in vitro E exposure. The presence of surface receptors for NE and E on splenic lymphocytes was determined using in vitro incubation with antagonists to alpha and beta receptors. These data suggest that there are alpha and beta receptor sites on lymphocytes for NE and E, and that these catecholamines have a regulatory role in plaque cell proliferation.

Animals↗
PubMed1990

Basic fibroblast growth factor: receptor-mediated internalization, metabolism, and anterograde axonal transport in retinal ganglion cells.

Basic fibroblast growth factor (bFGF) was radiolabeled and used in axonal transport studies to determine whether certain neuronal populations express functional receptors for bFGF. Unlike 125I-NGF, 125I-bFGF was not retrogradely transported in the adult rat sciatic nerve or from iris to trigeminal ganglion or superior cervical ganglion. However, after intraocular injection of 125I-bFGF into the posterior chamber of the eye of adult rats, radioactivity was detected within the retinal ganglion cell projections. This radioactivity was localized to the ipsilateral optic nerve and in the contralateral lateral geniculate body and the contralateral superior colliculus by using autoradiographic techniques. Direct measurement of the radioactivity in dissected brain regions was used to study the process of 125I-bFGF uptake and transport by retinal ganglion cells. The uptake and transport were specific for biologically active bFGF since neither denatured, biologically inactive 125I-bFGF nor 125I-NGF was taken up and transported. The uptake and transport of 125I-bFGF were saturable phenomena since they were blocked in the presence of excess, unlabeled bFGF. Wheat germ agglutinin, but not heparinase, blocked uptake and transport of 125I-bFGF, a finding that is consistent with the uptake being mediated by high-affinity bFGF receptors. Radioactivity from 125I-bFGF was transported in retinal ganglion cell axons in an anterograde direction at a maximum rate in excess of 1.7 mm/hr. No specific retrograde transport of bFGF to the retina was detected after 125I-bFGF was injected into the superior colliculus. The radioactivity from 125I-bFGF that accumulated in the superior colliculus was lost from this tissue with a half-life of about 22 hr. Autoradiography of proteins separated by SDS-PAGE demonstrated that 125I-bFGF was not substantially degraded in the retina after internalization within retinal ganglion cells. During anterograde transport, however, 125I-bFGF underwent limited proteolytic cleavage resulting in 3 prominent 125I-bFGF derivatives of molecular weights greater than 7000 Da. Although these were the major radioactive species recovered from the superior colliculus after intraocular injection, some intact 125I-bFGF was also detected within the innervated target. These results indicate that retinal ganglion cells express high-affinity receptors for bFGF, that these receptors mediate the internalization of bFGF, that internalized bFGF undergoes limited proteolytic cleavage, and that bFGF and its derivatives are anterogradely transported to the lateral geniculate body and the superior colliculus. These data raise the possibility that bFGF or its derivatives may act as an anterograde trophic factor in the visual system, a system that is known to undergo anterograde transneuronal cell death.

Animals↗
PubMed1978

East Coast fever: cultivation in vitro of cell-free schizonts and merozoites of Theileria parva and their immunogenicity in cattle.

Cell-free schizonts and merozoites of Theileria parva and Theileria lawrencei, derived from parasitized lymphoid cell lines, were propagated in vitro using enriched medium. Use of radioisotopic markers showed that the bovine cell-independent parasites passed through a limited but marked replication by day 4. If normal bovine RBC were inoculated in vitro with the cell-free merozoites, development of piroplasms in the RBC occurred. Electron microscopic studies of the merozoites and piroplasms revealed their structure to be similar to previous descriptions. Cattle inoculated with T parva merozoites and schizonts and later challenge exposed with homologous stabilate developed leukopenia, showed low macroschizont index, and survived longer than unvaccinated controls.

Animals↗
PubMed2004

Rab4 is an essential regulator of lysosomal trafficking in trypanosomes.

Rapid endocytosis and recycling of surface proteins are important processes common to most nucleated eukaryotic cells. The best characterized membrane recycling routes are mediated by the small GTPases Rab4 and Rab11, but the precise roles that these pathways play have not been fully elucidated. The protozoan Trypanosoma brucei has a highly developed endocytic system that is similar to that found in metazoans, albeit with an accelerated rate of membrane turnover. We have used this organism to investigate the function of the trypanosome orthologue of Rab4 (TbRAB4) by a combination of RNA interference, microscopy, and quantitative trafficking assays. RNA interference-mediated suppression of TbRAB4 expression inhibited the growth of trypanosomes without affecting receptor-mediated endocytosis or ligand recycling. Ultrastructural analysis indicated a major defect in membrane transport events. The accumulation of fluorescent dextran, a fluid-phase marker, was blocked in cells lacking TbRAB4 protein. Since most fluid-phase markers are transported to the lysosome in T. brucei, the effects of TbRAB4 RNA interference on lysosomal function were investigated. By immunofluorescence, the major lysosomal protein p67 became progressively dispersed in cells lacking the TbRAB4 protein. Pulse-chase analysis demonstrated that initial proteolytic cleavage and glycan processing of p67 were unaffected but that cells failed to accumulate the later p67 proteolyzed products associated with the lysosome. To confirm the role of TbRAB4 in lysosomal trafficking, a constitutively active mutant, TbRAB4QL, was expressed. TbRAB4QL was closely associated with an enlarged multivesicular body that contained p67. In addition, cells expressing TbRAB4QL showed increased fluid-phase uptake when compared with the parental line. Taken together, these data suggest that TbRAB4 is involved in regulation of fluid-phase traffic to the lysosome in T. brucei but not in receptor-mediated endocytosis or recycling. These data have implications for the role of Rab4 in other cell systems.

Animals↗
PubMed1995

Type 4a metabotropic glutamate receptor: identification of new potent agonists and differentiation from the L-(+)-2-amino-4-phosphonobutanoic acid-sensitive receptor in the lateral perforant pathway in rats.

Before the discovery of the metabotropic glutamate receptors (mGluRs), the glutamate analogue L-2-amino-4-phosphonobutanoic acid (L-AP4) was identified as a potent presynaptic inhibitor of evoked synaptic transmission in the lateral perforant pathway in rats. The localization and L-AP4 sensitivity of the mGluR4a subtype of mGluRs were consistent with the hypothesis that this receptor mediates the synaptic depressant effects of L-AP4 in the lateral perforant pathway. In the present study, the pharmacology of mGluR4a expressed in baby hamster kidney 570 cells was characterized and compared with that previously reported for the lateral perforant pathway responses. The endogenous excitatory amino acid L-aspartate was inactive at mGluR4a, whereas L-homocysteic acid was only 5-fold less potent than L-glutamate. These data suggest that L-homocysteic acid may be an endogenous agonist at mGluR4a. Of the 30 L-AP4 analogues examined, several compounds were identified as agonists at mGluR4a. The cyclopropyl-AP4 analogue (Z)-(+/-)-2-amino-2,3-methano-4-phosphonobutanoic acid inhibited forskolin-stimulated cAMP production with an EC50 of 0.58 microM, which is comparable to that of L-AP4 (EC50 = 0.43 microM). Two other cyclic analogues of L-AP4 were approximately 10-fold less potent as agonists at mGluR4a, i.e., (+/-)-1-amino-3-(phosphonomethylene)cyclobutanecarboxylic acid (EC50 = 4.4 microM) and (E)-(+/-)-2-amino-2,3-methano-4-phosphonobutanoic acid (EC50 = 7.9 microM). Comparison of the potencies of the compounds for activation of mGluR4a with their potencies for inhibition of lateral perforant pathway responses demonstrates that some compounds have comparable activities in the two systems, whereas several compounds are at least 10-fold more potent in one of the systems. In addition, although the mGluR antagonist (+)-alpha-methyl-4-carboxyphenylglycine blocked the effects of L-AP4 in the lateral perforant pathway, it did not block the effects of L-AP4 at the cloned receptor. These data provide evidence that mGluR4a does not mediate the effects of L-AP4 in the lateral perforant pathway, they provide new tools to identify the function of these receptors in the mammalian central nervous system, and they indicate that the effects of L-AP4 in the lateral perforant pathway are mediated by a (+)-alpha-methyl-4-carboxyphenylglycine-sensitive receptor.

Aminobutyrates↗
PubMedDate not supplied

Creating breakthroughs at 3M.

Most senior managers want their product development teams to create break-throughs--new products that will allow their companies to grow rapidly and maintain high margins. But more often they get incremental improvements to existing products. That's partly because companies must compete in the short term. Searching for breakthroughs is expensive and time consuming; line extensions can help the bottom line immediately. In addition, developers simply don't know how to achieve breakthroughs, and there is usually no system in place to guide them. By the mid-1990s, the lack of such a system was a problem even for an innovative company like 3M. Then a project team in 3M's Medical-Surgical Markets Division became acquainted with a method for developing breakthrough products: the lead user process. The process is based on the fact that many commercially important products are initially thought of and even prototyped by "lead users"--companies, organizations, or individuals that are well ahead of market trends. Their needs are so far beyond those of the average user that lead users create innovations on their own that may later contribute to commercially attractive breakthroughs. The lead user process transforms the job of inventing breakthroughs into a systematic task of identifying lead users and learning from them. The authors explain the process and how the 3M project team successfully navigated through it. In the end, the team proposed three major new product lines and a change in the division's strategy that has led to the development of breakthrough products. And now several more divisions are using the process to break away from incrementalism.

Economic Competition↗
PubMed1993

Dissociation of kainic acid lesion effects on the asymmetry of rotation and lateral head movements.

The present study tested the relationship between horizontal head movement asymmetry and rotation behavior after unilateral kainic acid (KA) lesions of the pontine reticular formation (PRF). In line with previous studies, the lesions decreased the rate of ipsilateral spontaneous head movements and spared contralateral spontaneous head movements. In contrast to previous studies, however, these lesions facilitated ipsilateral rather than contralateral rotation. Histological analysis revealed that the ipsilateral rotation may be accounted for by distant effects of the KA injection in the PRF on the ipsilateral substantia nigra (SN). We conclude that unilateral lesions consisting solely of the PRF lead to a preference for contralateral horizontal head movements which then channel rotated away from the lesioned side. KA injections in the PRF, however, are also associated with distant lesions within the ipsilateral extrapyramidal system which override the channeling effect of the contralateral head movements and induce instead ipsilateral rotation.

Animals↗
PubMed2003

Chick limbs with mouse teeth: an effective in vivo culture system for tooth germ development and analysis.

Mouse tooth germ development is currently studied by three main approaches: in wild-type and mutant mouse lines, after transplantation of tooth germs to ectopic sites, and in organ culture. The in vivo approaches are the most physiological but do not provide accessibility to tooth germs for further experimental manipulation. Organ cultures, although readily accessible, do not sustain full tooth germ development and are appropriate for short-term analysis. Thus, we sought to establish a new approach that would combine experimental accessibility with sustained development. We implanted fragments of embryonic day 12 mouse embryo first branchial arch containing early bud stage tooth germs into the lateral mesenchyme of day 4-5 chick embryo wing buds in ovo. Eggs were reincubated, and implanted tissues were examined by histochemistry and in situ hybridization over time. The tooth germs underwent seemingly normal growth, differentiation, and morphogenesis. They reached the cap, bell, and crown stages in approximately 3, 6, and 10 days, respectively, mimicking in a striking manner native temporal patterns. To examine mechanisms regulating tooth germ development, we first implanted tooth germ fragments, microinjected them with neutralizing antibodies to the key signaling molecule Sonic hedgehog (Shh), and examined them over time. Tooth germ development was markedly delayed, as revealed by poor morphogenesis and lack of mature ameloblasts and odontoblasts displaying characteristic traits such as an elongated cell shape, nuclear relocalization, and amelogenin gene expression. These phenotypic changes began to be reversed upon further incubation. The data show that the limb bud represents an effective, experimentally accessible as well as economical system for growth and analysis of developing tooth germs. The inhibitory effects of Shh neutralizing antibody treatment are discussed in relation to roles of this signaling pathway proposed by this and other groups previously.

Animals↗
PubMed2002

Changes in the prevalence of hepatitis C virus (HCV) genotype 4 in Calabria, Southern Italy.

The aim of this study was to assess changes in the prevalence of hepatitis C virus (HCV) genotypes, focusing on genotype 4, by surveying population of chronic hepatitis C patients within an area of Southern Italy. HCV-RNA was detected in serum using two commercial hepatitis C RNA PCR assays (Amplicor Roche Diagnostic System, and AmpliSensor HCV, Nuclear Laser Medicine). PCR products were analyzed for genotyping using a reverse hybridization of the amplified product by a line probe assay (INNO LIPA, Innogenetics). In our Institution we have previously observed, in a period of 18 months (January 1997-May 1998) an initial increase of the genotype 4 which appeared in 3.3% of HCV patients versus a percentage of 1.3%, during 1996. Later data obtained from 702 HCV-RNA positive patients, collected from June 1998 until December 1999 indicated a 3.7% of genotype 4. This percentage increased until to 4.7% in the most recent period studied (January 2000-February 2001). Drug addiction, blood transfusion and sporadically acquired infections represented the most frequent risk factors. In the Calabria region, genotype 1b, the most prevalent isolate (53.3%) and genotype 2a/2c (26.2%) were associated with older age, confirming our previous study. Genotype 4 was the fifth most prevalent genotype observed, just after 3a and 1a subtypes. Spread of genotype 4 in Calabria region is mostly associated to older age when compared to genotype 3a and 1a, but is statistically associated with a younger group of patients when compared with genotype 1b. In conclusion we demonstrated a fourfold increased prevalence of HCV genotype 4 during the last 5 years.

Adult↗
PubMed2001

Immunoreactive relaxin in seminal plasma of fertile boars and its correlation with sperm motility characteristics determined by computer-assisted digital image analysis.

Ejaculates from 10 mature fertile large white Yorkshire boars were used to examine the correlation between immunoreactive relaxin levels in seminal plasma and sperm motility characteristics. Seminal plasma levels of immunoreactive relaxin were measured by a time-resolved fluoroimmunoassay (TR-FIA). Motility characteristics were assessed using a CellSoft computer-assisted digital image analysis system. The mean +/- SD level of immunoreactive relaxin in seminal plasma was 2.61 +/- 0.62 ng/mL. When the correlation between seminal plasma levels of immunoreactive relaxin and parameters of sperm movement was examined, it was found that relaxin levels were significantly correlated with the percentage of motile spermatozoa (r=0.687, p < 0.05), curvilinear velocity (r=0.745, p < 0.05), straight line velocity (r=0.651, p < 0.05), mean amplitude of lateral head displacement (mean ALH) (r=0.844, p < 0.01) and the maximum amplitude of lateral head displacement (max ALH) (r=0.830, p < 0.01), but not with linearity, beat-cross frequency, or percentage of circular cells. Among these parameters, seminal plasma levels of immunoreactive relaxin showed the strongest correlation with the ALH parameter related to fertilizing ability. These results indicate that immunoreactive relaxin in boar semen may be necessary not only for normal sperm motility but also for normal fertility, suggesting that determination of the profile of immunoreactive relaxin in ejaculates may have value as a potential marker for predicting sperm fertilizing ability of boars.

Animals↗
PubMed2004

Chemical waves with line defects in the Belousov-Zhabotinsky reaction.

We report our experimental observations of line-defected chemical waves in a quasi-two-dimensional reaction-diffusion system of Belousov-Zhabotinsky reaction. The observed line defects are explicit, which can be directly monitored in real time. In the parameter space, the state of the chemical waves with line defects is located between two regimes of the defect-mediated turbulence. The line defects appear in target waves as well as in spiral waves. We demonstrate that the line defects come out in traveling waves as the later reorganize their spatial topologies to adapt to the change in the local dynamics from simple to complex oscillations or vice versa.

Journal Article↗
PubMed1987

Gas exchange during thoracotomy in children. A study using the single-breath test for CO2.

Gas exchange during thoracotomy was studied in 13 children aged 6 months to 14 years (median age 5 years), anaesthetized for repair of coarctation of the aorta or closure of a patent ductus arteriosus. All received halothane in equal parts of N2O/O2 supplemented with fentanyl. CO2 single-breath tests were obtained with a computerised on-line system based on the Servo ventilator. From signals for airway flow pressure, CO2 concentration and timing, the computer calculated the airway deadspace (VDaw) and the static compliance and resistance of the respiratory system. Given a value for PaCO2, the computer also calculated the physiological and alveolar deadspaces. Measurements were taken at six stages during the procedure, starting with the supine position before surgery. After turning to the lateral position, airway deadspace increased by 19%, thus increasing the physiological deadspace fraction. When the pleura was opened, both VDaw and PaO2 were reduced. When the upper lung was retracted, compliance was reduced and also PaO2 - the minimum value noted was 17.3 kPa. Hypoxic PaO2 values were possibly avoided because both ventilation and perfusion were reduced in the retracted lung. The alveolar deadspace fraction increased during these intra-operative stages. Although the net effect of the changes in airway and alveolar deadspace during surgery was a significant increase in physiological deadspace fraction (from 0.23 to 0.28), gas exchange could be maintained at the cost of only moderate increases in peak airway pressure: the mean increase was from 2.4 to 2.8 kPa (24 to 29 cmH2O).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Rheumatoid arthritis in the elderly. Prevalence and optimal management.

Elderly-onset rheumatoid arthritis (EORA), defined as rheumatoid arthritis (RA) with onset at age 60 years or over, differs slightly from younger-onset RA by a more equal gender distribution, a higher frequency of acute systemic onset with involvement of the shoulder, a higher disease activity, and, in later stages, more radiographic damage and functional decline. Several subsets of EORA are recognised, such as rheumatoid factor-positive RA, polymyalgia rheumatica and 'remitting seronegative symmetrical synovitis with pitting oedema'. These conditions can be difficult to distinguish from crystal-induced arthritis, osteoarthritis and paraneoplastic arthritis. The efficacy and tolerability of second-line drugs is similar in both age groups, but in the elderly caution is needed with the use of nonsteroidal anti-inflammatory drugs and prednisone.

Adrenal Cortex Hormones↗
PubMed1989

[Changes in myoglobin localization in the skeletal muscle of neuromuscular diseases demonstrated by immunohistochemistry and immunoelectron microscopy].

The changes of myoglobin localization in the skeletal muscle cells in Duchenne muscular dystrophy (DMD), myotonic dystrophy (MyD), and amyotrophic lateral sclerosis (ALS) were studied by immunohistochemistry and immunoelectron microscopy. In normal skeletal muscle cells, myoglobin was found in I band, Z line, mitochondrial outer membrane and inner membrane structures of sarcoplasmic reticulum and T tube. In contrast, the myoglobin staining of the I bands in degenerative muscle-cells of DMD and MyD was found rather diminished, and A bands, intraluminal spaces of the inner membrane system and intermyofibrillar spaces were myoglobin positive. Moreover, the I band of a myofibril which slipped out of other normally arranged myofibrils showed no myoglobin staining, but the distended intermyofibrillar spaces adjacent to the slipped myofibril showed a definite staining. In addition, there were dilated sarcoplasmic reticula showing the staining in their lumina, but the I bands neighboring them revealed a diminished staining. In DMD muscle, no staining was found in opaque fibers and some small sized fibers. In ALS muscle, myoglobin was usually positive in the I bands, but the small angulated fibers showed a variable staining. In the target fibers, central zone was not stained but intermediate zone showed altered myoglobin localization. These data indicate that (1) myoglobin localization in the muscle cells varies depending on the sorts of diseases and the grades of muscle cell degeneration, (2) myoglobin in dystrophic muscles fluxes from the muscle cells to extracellular spaces through the dilated sarcoplasmic reticula, T tubes and intermyofibrillar spaces, and (3) in DMD muscle, myoglobin also fluxes directly through the deteriorated plasma membrane in opaque fibers or through the plasma membrane altered due to dystrophin deficiency.

Adolescent↗
PubMed2005

Neuropeptide Y Y1 receptor mRNA in rodent brain: distribution and colocalization with melanocortin-4 receptor.

The central neuropeptide Y (NPY) Y1 receptor (Y1-R) system has been implicated in feeding, endocrine, and autonomic regulation. In the present study, we systematically examined the brain distribution of Y1-R mRNA in rodents by using radioisotopic in situ hybridization histochemistry (ISHH) with a novel sensitive cRNA probe. Within the rat hypothalamus, Y1-R-specific hybridization was observed in the anteroventral periventricular, ventromedial preoptic, suprachiasmatic, paraventricular (PVH), dorsomedial, ventromedial, arcuate, and mamillary nuclei. In the rat, Y1-R mRNA expression was also seen in the subfornical organ, anterior hypothalamic area, dorsal hypothalamic area, and in the lateral hypothalamic area. In addition, Y1-R hybridization was evident in several extrahypothalamic forebrain and hindbrain sites involved in feeding and/or autonomic regulation in the rat. A similar distribution pattern of Y1-R mRNA was observed in the mouse brain. Moreover, by using a transgenic mouse line expressing green fluorescent protein under the control of the melanocortin-4 receptor (MC4-R) promoter, we observed Y1-R mRNA expression in MC4-R-positive cells in several brain sites such as the PVH and central nucleus of the amygdala. Additionally, dual-label ISHH demonstrated that hypophysiotropic PVH cells coexpress Y1-R and pro-thyrotropin-releasing hormone mRNAs in the rat. These observations are consistent with the proposed roles of the central NPY/Y1-R system in energy homeostasis.

Animals↗
PubMed1999

[Metabotropic glutamate receptor: its ligands and function in the olfactory system].

The metabotropic glutamate receptors (mGluRs) consist of at least eight different subtypes. However, the lack of specific ligands for this class of receptors limited the characterization of their roles. In this study, a series of glutamate derivatives was systematically tested for agonist and antagonist activities for the mGluR subtypes, individually expressed in cell lines. Among various compounds tested, (2S, 1'R, 2'R, 3'R)-2-(2,3-dicarboxycyclopropyl) glycine (DCG-IV) was found to be an effective agonist for mGluR2 and alpha-methyl-4-carboxyphenylglycine (alpha M4CPG) was found to be an antagonist for both mGluR1 and mGluR2. Using DCG-IV, I showed that mGluR2 mediates presynaptic inhibition of GABA release from granule cells at the dendrodendritic synapse of the accessory olfactory bulb (AOB). This mechanism was considered to relieve a mitral cell from GABAergic inhibition and, furthermore, to be involved in lateral inhibition of surrounding mitral cells and thus enhancing the signal/noise ratio of olfactory sensation. I also show that an activation of mGluR2 in AOB by infusion of DCG-IV induces olfactory memory, which can mimic the pregnancy block phenomenon of female mice. This is the first report of a role of specific subtype of mGluR in the central nervous system.

Animals↗