bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for glutamate‐mediated activation of hippocampal neurons by glial calcium waves
Authors: Hassinger Tim D. , Atkinson Paul B. , Strecker George J. , Whalen L. Ray , Dudek F. Edward , Kossel Albrecht H. , Kater S. B.
Published: January 2005

Communication from astrocytes to neurons has recently been reported by two laboratories, but different mechanisms were thought to underlie glial calcium wave activation of associated neurons. Neuronal calcium elevation by glia observed in the present report is similar to that reported previously, where an increase in neuronal calcium was demonstrated in response to glial stimulation. In the present study hippocampal neurons plated on a confluent glial monolayer displayed a transient increase in intracellular calcium following a short delay after the passage of a wave of increased calcium in underlying glia. Activated cells displayed action potentials in response to glial waves and showed antineurofilament immunoreactivity. Finally, the N‐methyl‐D‐aspartate glutamate receptor antagonist DL‐2‐amino‐5‐phosphonovaleric acid and the non‐NMDA glutamate receptor antagonist 6,7‐dinitroquinoxaline‐2,3‐dione significantly reduced the responsiveness of neurons to glial calcium waves. Our results indicate that hippocampal neurons growing on hippocampal or cortical astrocytes respond to glial calcium waves with elevations in calcium and increased electrical activity. Furthermore, we show that in most cases this communication appears to be mediated by ionotropic glutamate receptor channels. © 1995 John Wiley & Sons, Inc.
Neurotrophin‐4/5, brain‐derived neurotrophic factor, and neurotrophin‐3 promote survival of cultured vestibular ganglion neurons and protect them against neurotoxicity of ototoxins
Authors: Lisa Zheng J. , Stewart Randall R. , Gao Wei‐Qiang
Published: January 2005

The ability of neurotrophin‐4/5 (NT‐4/5), brain‐derived neurotrophic factor (BDNF), neurotrophin‐3 (NT‐3), and nerve growth factor (NGF) to promote survival of postnatal rat vestibular ganglion neurons (VGNs) was examined in dissociated cell cultures. Of the four neurotrophins, NT‐4/5 and BDNF were equally effective but more potent than NT‐3 in promoting the survival of VGNs. In contrast, NGF showed no detectable effects. As expected, TrkB‐IgG (a fusion protein of extracellular domain of TrkB and Fc domain of human immunoglobulin G) specifically inhibited the survival‐promoting effects by NT‐4/5 or BDNF and TrkC‐IgG fusion protein completely blocked that of NT‐3. Immunohistochemistry with TrkB, TrkA, and p75 antisera revealed that VGNs made TrkB and p75 proteins, but not TrkA protein. Ototoxic therapeutic drugs such as cisplatin and gentamicin often induce degeneration of hair cells and ganglion neurons in both auditory and vestibular systems that leads to impairment of hearing and balance. When cisplatin and gentamicin were added to the dissociated VGN culture in which the hair cells were absent, additional cell death of VGNs was induced, suggesting that the two ototoxins may have a direct neurotoxic effect on ganglion neurons in addition to their known toxicity on hair cells. However, if the cultures were co‐treated with neurotrophins, NT‐4/5, BDNF, and NT‐3, but not NGF, prevented or reduced the neurotoxicity of the two ototoxins. Thus, the three neurotrophins are survival factors for VGNs and are implicated in the therapeutic prevention of VGN loss caused by injury and ototoxins. © 1995 John Wiley & Sons, Inc.
Tenascin‐C mRNA is expressed in cranial neural crest cells, in some placodal derivatives, and in discrete domains of the embryonic zebrafish brain
Authors: Tongiorgi Enrico , Bernhardt Robert R. , Zinn Kai , Schachner Melitta
Published: January 2005

A partial zebrafish tenascin‐C cDNA clone was isolated from an embryonic zebrafish cDNA library on the basis of homology to mouse tenascin‐C. The expression pattern in the head of embryonic zebrafish was analyzed by in situ hybridization. Tenascin‐C mRNA was detected in neural crest cells during the period of their migration and differentiation. Expression also occurred in differentiating placodal tissues and in mesodermal cells. In the developing brain, tenascin‐C mRNA was expressed in specific domains. In the hindbrain the pattern of the domains was dynamic. At 18 to 22 h postfertilization, expression was widespread in rhombomeres 3, 5, and 6, confined to periventricular cells in rhombomere 2, and not detectable in rhombomere 4. At 32 h postfertilization, tenascin‐C was expressed at the rhombomere boundaries. In contrast to the hindbrain, the pattern in the forebrain and midbrain did not show any major changes between 22 and 32 h postfertilization. Domains expressing tenascin‐C alternated with regions devoid of it. The most anterior domain of expression was observed at the telencephalic‐diencephalic border, surrounding the optic recess. A second domain, at the border between the diencephalon and the midbrain, and a third domain, in the caudal midbrain tegmentum, appeared restricted to the basal plate. Additionally, expression of tenascin‐C mRNA was detected in the hypothalamus and in the developing epiphysis. These expression patterns suggest that tenascin‐C may play a role in neural crest cell migration and during the differentiation of neural crest, placodal, and mesodermal derivatives. In the developing brain, tenascin‐C may be involved in the consolidation of different regional identities. © 1995 John Wiley & Sons, Inc.
Comprehensive analysis of the extracellular proteins from Xanthomonas campestris pv. campestris B100
Authors: Watt Steven Alexander , Wilke Andreas , Patschkowski Thomas , Niehaus Karsten
Published: January 2005

The extracellular proteome of Xanthomonas campestris pv. campestris (Xcc) cultivated in minimal medium was isolated from the cell‐free culture supernatant and separated by two‐dimensional gel electrophoresis. This technique resolved 97 clearly visible protein spots, which were excised, digested with trypsin and identified on the basis of their peptide mass fingerprints generated by matrix assisted laser desorption/ionisation‐time of flight‐mass spectrometry. Using this approach 87 different proteins could be distinguished. The Signal P software predicted putative signal peptides for 53% of the extracellular proteins. These proteins are probably transported over the inner membrane and are localized in the periplasm, the outer membrane or secreted into the extracellular space. Among the secreted proteins are 11 degradative enzymes, which are involved in pathogenesis of Xcc. The proteins without obvious secretion signals are known to serve functions in the cytosol. How the cytosolic proteins are delivered to the extracellular space remains unclear.
Kinetics and mechanism of reaction of benzyl bromide with copper in dimethylacetamide
Authors: Egorov Anatoly M. , Matyukhova Svetlana A. , Anisimov Alexander V.
Published: January 2005

The reaction of copper with various benzyl bromides in dimethylacetamide was studied. In the absence of atmospheric oxygen, oxidative dissolution of copper occurred by the mechanism of single electron transfer with the formation of 1,2‐diphenylethane and copper(I) complexes. The kinetic and thermodynamic parameters of the reaction have been obtained and the reaction mechanism is discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Changes in neurotransmitter uptake in the spinal cord following peripheral nerve injury
Authors: Somps Christopher J. , Boyajian Christine L. , Luttges Marvin W.
Published: January 2005

Changes in neurotransmitter systems of the spinal cord were studied in response to peripheral nerve injury. The uptake and compartmentalization of radiolabeled spinal cord neurotransmitters and transmitter precursors were examined as a function of time following unilateral sciatic nerve crush in adult mice. Accumulation of transmitter was measured within synaptosomally enriched fractions prepared using combinations of differential and density gradient centrifugations. The amount of transmitter substance recovered from these fractions was strongly depedent upon the amount of time following nerve injury and on the specific transmitter or precursor being examined (GABA, glutamate, glycine, and choline chloride). However, for each of these substances, uptake values returned to control levels within nine to twelve days after nerve crush. Localization of GABA changes postcrush revealed reciprocal differences between ipsilateral and contralateral sides of the spinal cord, as well as differences between segmental levels. Altered GABA uptake may reflect changes in the postcrush microchemical environment present during tissue processing, but may also be related to direct changes in the synaptic binding, transport, and compartmentalization of transmitter substance. The time course, magnitude, and direction of these neurochemical changes follow those observed neurophysiologically, and may thus underlie injury‐induced short‐term (days) alterations reported in primary afferent depolarizations, cross cord responses, and other spinal mechanisms.
Cerebellin and related postsynaptic peptides in the brain of normal and neurodevelopmentally mutant vertebrates
Authors: Morgan J. I. , Slemmon J. R. , Danho W. , Hempstead J. , Berrebi A. S. , Mugnaini E.
Published: January 2005

The rat cerebellum was previously shown to contain two polypeptides, a hexadecapeptide termed cerebellin and an apparent metabolite des‐Ser1‐cerebellin. The cerebellins have a high degree of sequence homology with residues 625–641 of the polyimmunoglobulin (polyIg)‐receptor adjacent to its membrane‐spanning domain. Since the cerebellins are localized in Purkinje cells and enriched in synaptosomes, this might indicate that cerebellin is a specific proteolytic cleavage fragment of a synaptic protein involved in the transcytosis of an unknown ligand. Using a specific cerebellin radioimmunoassay described here combined with high‐performance liquid chromatography, cerebellin immunoreactivity could be demonstrated in the cerebella of all vertebrates examined from man to chicken. Cerebellin immunoreactivity is localized to Purkinje cells in the rat, mouse, and chicken. Furthermore, cerebellin expression is under developmental regulation in both the chicken and mouse. In addition, neurodevelopmental mutations of mice that eliminate granule cells cause a large deficit in cerebellin levels, suggesting some form of transneuronal regulation.
Reduction of postjunctional fold density and depth in dystrophic mice
Authors: Tremblay Jacques P. , Grégoire Laurent , Sasseville Rachelle , Guay Gabrielle , Belhumeur Céline
Published: January 2005

A total of 769 neuromuscular junction profiles (on 221 muscle fibers) from 21 normal (C57BL/6J +/+), 6 heterozygous (C57BL/6J dy2J/+) and 22 homozygous dystrophic (C57BL/6J dy2 J/dy2J) gastrocnemius were photographed in electron microscopy. The fast and slow twitch muscle fibers were differentiated by the width of the Z lines. The number of secondary postjunctional folds per unit length of synaptic cleft was lower in dystrophic than in normal animals. Intermediate values were obtained in heterozygous animals. The length of the postsynaptic membrane was measured and normalized by dividing it by the length of the cross‐section through the synaptic cleft. This normalized length of postjunctional membrane was significantly reduced by 45% in dystrophic animals relative to normals animals and by 41% relative to heterozygous animals. The depth of the secondary folds was also significantly reduced in dystrophic animals relative to normal animals in both fast and slow twitch fibers. These morphometric changes of the postjunctional membrane were observed on NMJs whose nerve terminals were not significantly modified by the dystrophic process and were sometimes observed on apparently normal muscle fibers.
Control of feeding and sexual behaviors by neuropeptide Y: Physiological implications
Authors: Kalra Satya P. , Clark John T. , Sahu Abhiram , Dube Michael G. , Kalra Pushpa S.
Published: January 2005

Recent evidence suggests that a variety of hypothalamic neuropeptides may mediate interneuronal communication to coordinate diverse neuroendocrine and behavioral functions. In this work, we describe the effects of neuropeptide Y (NPY) on feeding and sexual behaviors. We observed that central administration of bolus NPY stimulated a robust, dose‐related feeding response in satiated male and female rats. Continuous NPY receptor activation also evoked dose‐related, intermittent feeding in a manner normally observed during nocturnal feeding. It appears that the paraventricular nucleus in the hypothalamus may be the primary site of NPY action because the anticipated reciprocal changes in NPY concentrations, in response to food deprivation followed by ad libitum food intake, occurred only in this site. Additional findings revealed that NPY‐induced feeding may follow either substantial reduction or complete restraint of an inhibitory influence on feeding mediated by α2‐adrenoreceptor systems in satiated rats. Further, NPY was found to suppress male and female sexual behaviors. The suppressive effects on sexual behavior were apparent prior to or at the time of the onset of feeding after NPY administration. These observations may provide a neurochemical basis for clinical and animal studies on disorders of feeding associated with diminished reproductive functions.
Norepinephrine throughout the spinal cord of the cat: I. Normal quantitative laminar and segmental distribution
Authors: Massari V. John , Park Chan H. , Suyderhoud Johan P. , Tizabi Yousef
Published: January 2005

Norepinephrine (NE) concentrations were measured by radioenzymatic assay in microdissected individual laminae of each segment of the cat spinal cord. Norepinephrine was detected in all areas of the spinal gray matter and showed more than a 7‐fold difference in concentration between the laminae with the highest and lowest NE. The cervical, thoracic, and lumbosacral spinal regions showed significant interlaminar differences in NE. Intersegmental changes in NE were seen within single laminae of the thoracic and lumbosacral spinal cord, but not in the cervical spinal cord. A significant rostral to caudal, increasing regional gradient of NE was observed from the cervical to lumbosacral spinal cord in laminae I‐III, V, VI, VII, and IX. In the intermediolateral cell column (IML), epinephrine concentrations were 2 to 5% of NE. Neither neurotransmitter showed a significant intersegmental variation in the IML. These data should prove useful in further defining the precise role of NE in specific regions of the spinal cord that mediate sensory, motor, autonomic, or propriospinal functions.
α‐Melanocyte‐stimulating hormone structure‐activity studies: Comparative analysis of melanotropic and CNS bioactivities
Authors: Sawyer Tomi K. , Hadley Mac E. , Hruby Victor J. , de Lauro Castrucci Ana Maria , Staples Douglas J. , Farah John , L. O'donohue Thomas
Published: January 2005

The structure‐activity relationships in vitro of α‐MSH (α‐melanocyte‐stimulating hormone, α‐melanotropin) analogs as determined on normal and transformed (melanoma cell) melanocyte bioassays are summarized. Specifically, the characterization of potent and metabolically stable melanotropic agonist analogs and a newly discovered antagonist of α‐MSH are highlighted. Comparison of these data versus the known structure‐activity relationships of α‐MSH related to CNS bioactivities suggests the existence of nonclassical α‐MSH receptor‐mediated pathways or, perhaps, a yet undefined endogenous neuropeptidergic pathway(s) having different selectivities for α‐MSH analogs. In summary, several of the α‐MSH analogs reported here may be useful molecular probes in future strategies aimed at the identification and systematic characterization of both peripheral and central α‐MSH receptors.
Cardiovascular effects and modulation of noradrenergic neurotransmission following central and peripheral administration of neuropeptide Y
Authors: Westfall Thomas C. , Martin John , Chen Xiaoli , Ciarleglio Anita , Carpentier Suzanne , Henderson Kristina , Knuepfer Mark , Beinfeld Marge , Naes Linda
Published: January 2005

Experiments have been conducted to evaluate the effect of neuropeptide Y (NPY) administered at three distinct levels of the nervous system: (1) the posterior hypothalamic nucleus, (2) the spinal cord, and (3) the vascular noradrenergic neuroeffector junction. It was observed that NPY produced varying cardiovascular effects at these three distinct sites of the nervous system. Microinjections into the posterior hypothalamic nucleus resulted in an increase in blood pressure, which was reduced by prior microinjection of a muscarinic or H1‐histamine antagonist but not an H2‐histamine antagonist. In addition to the involvement of histaminergic and cholinergic pathways, the pressor effect of NPY appers to result from an increase in sympathetic outflow. NPY was also seen to decrease the potassium‐induced release of norepinephrine (NE) from slices obtained from the posterior hypothalamic nucleus. In contrast to what was observed in the hypothalamus, the intrathecal injection of NPY at a level of T4 or T10 in anesthetized or T10 in unanesthetized rats resulted in a depressor effect as well as a decrease in heart rate. Both an α2‐ and β‐adrenoceptor antagonist reduced the NPY effect. The depressor effect of intrathecal NPY was attenuated in rats pretreated with reserpine as well as in Spontaneously Hypertensive rats (SHR). These data suggest that the effects of NPY are closely associated with sympathetic preganglionic neurons in the spinal cord. At the vascular noradrenergic neuroeffector junction, NPY decreased the nerve stimulation‐induced release of NE while potentiating the contractile response. Moreover, NPY potentiated the increase in perfusion pressure of the perfused mesenteric arterial bed in response to angiotensin, vasopressin, or phenylephrine. The potentiation of smooth muscle contraction produced by NPY was shared by the homologous peptide, peptide YY (PYY) and to a lesser extent, pancreatic polypeptide (PPY). The prejunctional effect of NPY was less and the postjunctional effect greater in SHR compared with that in normotensive rats. The evidence obtained in these studies supports a cotransmitter role of NPY with NE in central and peripheral noradrenergic neurons. Moreover, NPY may be implicated in the development and maintenance of hypertension in the SHR.
Hormonal regulation of somatostatin messenger RNA
Authors: Baldino Frank , Fitzpatrick‐McElligott Sandra , M. O'kane Teresa , Gozes Illana
Published: January 2005

The ability of gonadal steroids to regulate the expression of the somatostatin gene in several regions of the CNS was investigated with in situ hybridization histochemistry. The amount of somatostatin mRNA was found to be significantly decreased 2–3 weeks after ovariectomy or orchidectomy in the periventricular hypothalamus, the ventromedial nucleus of the hypothalamus, and the medial and central nuclei of the amygdala. Treatment of gonadectomized rats with estradiol benzoate or testosterone enanthate reversed this decrease in somatostatin mRNA. No significant effect was noted in the cerebral cortex or bed nucleus of the stria terminalis. In some regions, there was a high degree of convergence between the distribution of neurons containing estrogen/ androgen receptors and somatostatin neurons that were responsive to gonadectomy. These results suggest that sex steroids regulate the expression of somatostatin through an action at the level of transcription.
Ultrastructural changes in acetylcholinesterase activity in the deafferented spinal trigeminal nucleus
Authors: Wilson Frances R. , Westrum Lesnick E. , Broderson Stevan H.
Published: January 2005

Acetylcholinesterase (AChE) activity was investigated in synaptic areas of the cat spinal trigeminal nucleus (pars interpolaris and pars caudalis) ipsilateral and contralateral to complete retrogasserian rhizotomy. Vibratome sections of tissue taken from animals of 1, 3, 6, 14, and 21 days survival were examined by electron microscopy following a histochemical reaction for AChE activity employing a method based on the Karnovsky‐Roots technique for demonstrating reaction product. As degeneration progressed with survival time, enzymatic activity was initially reduced in synaptic clefts of injured afferent terminals and subsequently was enhanced throughout the extracellular space, including within synaptic clefts of possibly reinnervated sites. These changes in enzymatic activity with primary deafferentation are discussed in relation to the process of reinnervation, the development of neuronal hyperactivity, and possible noncholinergic functions of AChE.
Biphasic modulation of evoked [3H]D‐aspartate release by D‐2 dopamine receptors in rat striatal slices
Authors: Peris Joanna , Dwoskin Linda P. , Zahniser Nancy R.
Published: January 2005

It has been hypothesized that dopamine (DA) inhibits glutamate release from corticostriatal fibers via presynaptically located D‐2 DA receptors although the evidence presented in the literature has not been conclusive. In the present experiments, the effect of D‐2 receptor ligands on K+‐stimulated tritium release from rat striatal slices preloaded with the nonmetabolizable glutamate analog [3H]D‐aspartate ([3H]ASP) was measured. The D‐2 receptor antagonist S‐sulpiride increased stimulated [3H]ASP release by 75% (EC50 value = 240 nM) and the biologically less‐active isomer R‐sulpiride, although equally effective, was tenfold less potent. The D‐2 receptor agonists pergolide and (+)‐4‐propyl‐9‐hydroxynapthoxazine (+PHNO) inhibited [3H]ASP release at nM concentrations; however, this effect was small (20%). This low efficacy of the exogenous agonists was apparently due to competition by high concentrations of endogenous DA since the effect of pergolide was increased in rats whose striatal DA levels were decreased by 97%. These data support the hypothesis that D‐2 DA receptors modulate [3H]ASP release in an inhibitory fashion. However, when the agonists were tested at lower concentrations, [3H]ASP release was increased significantly by 20% in control rats and 60% in DA‐depleted rats. Both the facilitory and inhibitory effects of pergolide were blocked by 10 μM S‐sulpiride, suggesting D‐2 receptor mediation. In addition, the facilitory effect of pergolide was blocked by tetrodotoxin (TTX) and by the GABAA antagonist bicuculline, implying mediation of this D‐2 effect by an inhibitory GABAergic interneuron. The inhibitory effect of pergolide was decreased by the muscarinic antagonist atropine. These data are consistent with the hypothesis that receptors mediating both facilitory and inhibitory D‐2 modulation of [3H]ASP release are located on interneurons rather than directly on the corticostriatal afferents.
Selective cortical infarction reduces [3H]sulpiride binding in rat caudate‐putamen: Autoradiographic evidence for presynaptic D2 receptors on corticostriate terminals
Authors: Filloux F. , Liu T. H. , Hsu C. Y. , Hunt M. A. , Wamsley James K.
Published: January 2005

Although the existence of presynaptic D2 dopamine receptors on corticostriate terminals has been supported by numerous receptor‐bindding studies, recent autoradiographic data has failed to demonstrate loss of striatal D2 receptors following cortical lesions. In the present study, Long‐Evans rats were subjected to unilateral middle cerebral artery (MCA) infarction in order to produce reproducible lesions of the neocortex without damaging subcortical structures. Animals were sacrificed 2 and 4 wk following lesion and brains were prepared for receptor autoradiography. D2 receptors were studied using the selective ligand [3H]sulpiride, while D1 dopamine receptors were examined using [3H]SCH 23390. Sodium‐dependent, high‐affinity choline uptake sites were labeled with [3H]hemicholinium‐3, thereby providing a quantitative measure of cholinergic neuronal integrity. Unilateral cortical infarction resulted in approximately a 20% reduction in [3H]sulpiride binding in several discrete regions of the ipsilateral caudate‐putamen (CPu), but not in the nucleus accumbens. D2 receptor binding was also reduced significantly in some areas of the contralateral CPu when compared with [3H]sulpiride binding in shamoperated, control animals. In contrast, D1 receptors as identified by [3H SCH 23390 and high‐affinity choline uptake sites labeled with [3H]‐HC‐3] were not affected by the cortical lesion. The results provide autordiographic confirmation of the existence of presynaptic D2 receptors on corticostriate terminals.
Modified coeruleo‐cortical noradrenergic neurotransmission after serotonin depletion by PCPA: Electrophysiological studies in the rat
Authors: Ferron André
Published: January 2005

To detect eventual modifications in the efficacy of the noradrenergic (NA) coeruleo‐cortical system after serotonin (5‐HT) depletion by parachlorophenylalanine (PCPA), three electrophysiological parameters were investigated in urethane‐anesthetized rats which were treated for 2 days with daily injections of this inhibitor of 5‐HT synthesis. (1) The spontaneous activity of locus coeruleus (LC) noradrenergic neurons showed a significant increase in PCPA‐treated compared to control rats (4.3 vs. 2.6 Hz). (2) The sensitivity of NA autoreceptors was measued in the LC by the effect of intravenous administrations of clonidine or microiontophoretic applications of NA on spontaneous neuronal firing. In treated rats, clonidine and NA induced a lesser reduction of LC neuron firing than in the controls (27 vs. 75% decreases and 1,367 vs. 280 nC, respectively). (3) The responsiveness of cortical neurons to electrical stimulation of the LC was assessed by peristimulus time histograms in the dorsal fronto‐parietal cortex. Following stimulation at 2 or 4 Hz, a majority of spontaneously firing cortical units was inhibited by electrical stimulation of the LC, but the percentage of such units was reduced and showed a decreased responsiveness after PCPA treatment. These findings suggest that following 5‐HT depletion by PCPA, cortical NA neurotransmission is makedly reduced in its efficacy in spite of some increase in the spontaneous activity of coeruleo‐cortical NA neurons.
Increased neuronal responsiveness to cholecystokinin and dopamine induced by lesioning mesolimbic dopaminergic neurons: An electrophysiological study in the rat
Authors: Debonnel Guy , de Montigny Claude
Published: January 2005

In the rat, cholecystokinin (CCK) and dopamine (DA) coexist in a subpopulation of neurons of the ventral tegmental area (VTA) projecting to the nucleus accumbens. However, in the dorsal hippocampus, dopaminergic projections from the VTA do not contain CCK, the latter neurotransmitter being mainly localized in intrinsic hippocampal neurons. The present experiments were undertaken in order to compare the interactions of CCK and DA and the effects of lesioning VTA dopaminergic neurons in a region where these neurotransmitters coexist and in one where they do not. The effects of microiontophoretic applications of CCK, kainate (KA), glutamate (GLU) and DA were determined in control rats and in rats pretreated with a local injection of 6‐hydroxydopamine (6‐OHDA) in the VTA. In the nucleus accumbens and in the hippocampus of intact rats, DA exerted a similar depressant effect whether applied during CCK‐, KA‐ or GLU‐induced activations. The 6‐OHDA lesion enchanced responsiveness of accumbens neurons to KA, GLU and CCK (the responsiveness to this latter peptide being increased by more than 15‐fold) and the depressant effect of DA when applied during neuronal activation by KA or GLU but not when the same neurons were activated with CCK. In the dorsal hippocampus, the 6‐OHDA lesion enhanced neuronal responsiveness to KA and DA in the CA1, but not in the CA3 region, whereas the responsiveness to KA and DA in the CA1, but not in the CA3 region, whereas the reponsiveness to CCK remained unchanged in both regions. These results suggest a physiological role for the coexistence of CCK and DA in the nucleus accumbens. The induction of a supersensitivity to DA in the CA1, but not in the CA3, region of the dorsal hippocampus following a VTA lesion is consistent with the regional distribution of the dopaminergic innervation in this structure.
Synaptic structural plasticity: Role of synaptic shape
Authors: Markus Etan J. , Petit Ted L.
Published: January 2005

Recent research has indicated that synaptic curvature is an important and potentially critical plastic feature of the synapse. Alterations in synaptic shape are related to synaptic function, being found both during maturation and in adulthood following neuronal activation. In this paper we review the evidence supporting synaptic shape as a plastic feature of synaptic structure. We also propose several mechanisms which might underlie these changes in shape. Finally, we suggest the possible functional role of alterations in synaptic curvature, including its potential in altering synaptic transmission efficacy.
Differential sparing of somatostatin‐neuropeptide y and cholinergic neurons following striatal excitotoxin lesions
Authors: Beal M. Flint , Kowall Neil W. , Swartz Kenton J. , Ferrante Robert J. , Martin Joseph B.
Published: January 2005

We previously found that quinolinic acid striatal excitotoxin lesions result in a relative sparing of somatostatin and neuropeptide Y neurons. In the present study we examined dose‐response effects of excitotoxins acting at the three subtypes of glutamate receptors: N‐methyl‐D‐aspartate (AA1), quisqualate (AA2), and kainic acid (AA3). Concentrations of both somatostatin‐like immunoreactivity (SLI) and neuropeptide a Y‐like immunoreactivity (NPYLI) were compared with those of substance P‐like immunoreactivity (SPLI) and GABA. Kainic acid (AA3), quisqualic acid (AA2), and AMPA (AA2) resulted in dose‐dependent reductions in all four neurochemical markers examined, while N‐methyl‐D,L‐aspartate (AA1) and quinolinic acid (AA1) resulted in relative sparing of SLI and NPYLI. At doses of each excitotoxin which resulted in comparable 50% reductions in both GABA and SPLI only N‐methyl‐D,L‐aspartate and quinolinic acid had no significant effect on concentrations of SLI and NPYLI. The relative sparing of somatostatin‐neuropeptide Y neurons was confirmed histologically by using histochemical staining for NADPH‐diaphorase neurons combined with either Nissl stains, or immunohistochemical staining for enkephalin. Lessions with N‐methyl‐D‐aspartate agonists resulted in preferential sparing of NADPH‐diaphorase neurons while these neurons were more vulnerable than other neurons to kainic acid or AMPA. Choline acetyltransferase neurons were relatively spared, as compared with other neurons, by agents acting at all three glutamate receptor subtypes. N‐methyl‐D,L‐aspartate lesions were blocked with MK‐801, while there was no effect on quisqualic acid or kainic acid lesions. The relative sparing of somatostatin‐neuropeptide Y neurons following striatal excitotoxin lesions with N‐methyl‐D‐aspartate (AA1) agonists probably reflects a paucity of AA1 receptors on these neurons. Since these neurons are also spared in Huntington's disease, excitotoxins acting at the N‐methyl‐D‐aspartate (AA1) site provide an improved neurochemical model of this illness.
Synaptogenesis in the stratum griseum superficiale of the rat superior colliculus
Authors: Warton S. S. , McCart R.
Published: January 2005

The time course of synaptogenesis in the visual part of the superior colliculus (SC) of pigmented rats has been studied. The number of synaptic profiles per unit area and volume of neuropil in the stratum griseum superficiale (SGS) was estimated in seven groups of animals at ages 3, 9, 15, 21, 30, 49 and 85 days after birth.

At 3 days only 1.5 ± 0.06 synaptic contacts per unit area and 5.5 ± 0.18 per unit volume were found. Most of them were immature contacts between growing processes. The density of synaptic contacts increased slowly during the first week. By day 9, 4.1 ± 0.25 and 13.4 ± 0.66 synaptic contacts were counted per unit of area and volume, respectively. A rapid synaptic proliferation occurred during the next 3 weeks and there were 7.7 ± 0.27 and 25.5 ± 1.04 synaptic contacts per unit area and volume at 15 days, 21.1 ± 1.70 and 86.4 ± 5.11 at 21 days, and 25.9 ± 1.20 and 96.7 ± 3.48 at 30 days. At the same time, the synaptic population gradually acquired more mature morphological characteristics: the pre‐ and postsynaptic structures became more specialized, the number of synaptic vesicles within presynaptic structures increased, and the synaptic junctional apposition became defined. After 30 days, a decrease in the density of synaptic profiles was recorded: 23.9 ± 0.44 and 79.8 ± 1.43 per unit area and volume of neuropil at 49 days and 13.4 ± 0.53 and 49.7 ± 2.40 at 85 days, respectively. Thus, after the phase of synaptic proliferation, a significant reduction of synaptic density occurred in the SGS neuropil until it was stabilized at the adult level by the third month of life.

Considering the data available on the development of the retinal and visual cortical projections to the SC, the process of synaptic elimination, which takes place after the first postnatal month, does not appear to be directly connected with segregation of these particular projections.
Direct demonstration of D1 dopamine receptors in the bovine parathyroid gland using the D1 selective antagonist [125I]‐SCH 23982
Authors: Monsma Frederick J. , Sibley David R.
Published: January 2005

The presence of D1 dopamine receptors in the parathyroid gland has been proposed based on the demonstration of dopaminergic regulation of adenylate cyclase activity and parathyroid hormone release in dispersed bovine parathyroid cells. Using a radioiodinated D1 selective antagonist [125I]‐SCH 23982, we have now directly labeled and characterized the D1 dopamine receptors in bovine parathyroid gland membranes.

[125I]‐SCH 23982 binds in a saturable manner with high affinity and low nonspecific binding to membranes prepared from bovine parathyroid glands. D1 dopamine receptors are present in this preparation at a concentration of ≈︁130 fMoles/mg protein and [125I]‐SCH 23982 binding increases with increasing protein concentration in a linear fashion. Determination of the Kd using the association (k1) and dissociation (k‐1) rate constants revealed good agreement with the Kd determined by saturation analysis (390 pM vs. 682 pM, respectively). Inhibition of 0.3 nM [125I]‐SCH 23982 binding by a series of dopaminergic antagonists verified the D1 nature of this binding site, exhibiting appropriate affinities and rank order of potency. The competition curves of all antagonists exhibited Hill coefficients that were not significantly different from 1. Inhibition of [125I]‐SCH 23982 binding by dopamine and other dopaminergic agonists revealed the presence of high and low affinity agonist binding sites. Addition of 200 μM GppNHp effected a complete conversion of high affinity dopamine binding sites to a homogeneous population of low affinity dopamine sites. The D1 receptors identified in the parathyroid gland with [125I]‐SCH 23982 appear to be pharmacologically identical with those previously characterized in the central nervous system.

These results demonstrate that the bovine parathyroid gland, which possesses well‐characterized functional responses to dopaminergic stimulation, may provide a single cell‐type model system for future investigation of the molecular events involved in D1 dopamine receptor/response coupling and regulation.
Effects of hypothyroidism on high‐affinity vasopressin binding sites in developing hippocampal synaptosomes
Authors: Rami Abdelhaq , Barberis Claude , Clos Jean
Published: January 2005

Binding sites of vasopressin (VP) have been characterized in the hippocampal synaptic plasma membranes of developing normal and hypothyroid rats using a highly specific tritiated VP antagonist, d(CH2)5Tyr(Me)VP (V1 type). This antagonist bound to an apparently homogeneous population of specific sites with an affinity ten times higher than that of VP itself. The total amount of synaptosomal protein in 15‐day‐old normal rats represented about 50% of the adult value, but the density of binding sites was already maximal and remained constant thereafter, supporting the concept of an early development of an extrahypophyseal vasopressinergic hippocampal system. Thyroid deficiency specifically reduced the amount of synaptosomal protein. However, the binding site density in the synaptsomal fraction appeared to be relatively well preserved from hypothyroidism, although there was a transient decrease in the apparent affinity of the ligand. These data suggest that thyroid hormones are slightly involved in the early development of high‐affinity VP receptors.
Inhibitory effect of norepinephrine on the single‐unit activity of caudally projecting paraventricular neurons
Authors: Kim Yang I. , Dudley Carol A. , Moss Robert L.
Published: January 2005

The role of norepinephrine (NE) in controlling the single‐unit activity of paraventricular (PVN) neurons projecting to or passing through the caudal ventrolateral medulla (CVLM) was investigated in adult male rats anesthetized with urethane. Of 72 PVN neurons studied, 19 were antidromically activated by CVLM stimulation (Group I) and 48 were antidromically activated by posterior pituitary (PP) stimulation (Group II). The remaining 5 neurons were antidromically driven by both CVLM and PP stimulation (Group III). In 14 of the 19 Group I neurons and in all the 5 Group III neurons, iontophoretically applied NE was demonstrated to inhibitory to the single‐unit activity. No excitatory effect of NE was observed. In contrast, both excitatory and inhibitory actions of NE were observed in the Group II neurons. Of 37 Group II neurons tested, 28 were excited and 7 were inhibited by NE. The inhibitory effect of NE in Group I and Group III neurons was selectively blocked by the alpha antagonist, phentolamine, that was coiontophoresed with NE, but not by the beta antagonist, timolol (n = 9). The unit activity of Group I neurons that were inhibited by NE was not altered by an increase in arterial blood pressure (n = 3), whereas the unit activity of one NE‐insensitive Group I neuron was decreased by an increase in blood pressure.

Taken together, the results suggest that NE plays an alpha‐adrenoreceptor‐mediated inhibitory role in controlling the single‐unit activity of caudally projecting PVN neurons. These neurons include a subpopulation of PVN neurons that project caudally as well as to the PP. The possible function associated with the NE‐sensitive, caudally projecting PVN neurons may be other than the regulation of blood pressure.
Long‐term blockade of the dopamine uptake complex by metaphit, an isothiocyanate derivative of phencyclidine
Authors: Zimänyi Ildikó , Jacobson Arthur E. , Rice Kenner C. , Lajtha Abel , Reith Maarten E. A.
Published: January 2005

[3H]Mazindol was used to label the dopamine uptake complex in mouse striatum in vitro in the presence and absence of metaphit, an isothiocyanate derivative of phencyclidine. In some experiments, metaphit was present in the incubation fluid throughout the procedure in other experiments it was eliminated by several washings and centrifugations. It was found that after removal of the metaphit by washing and centrifugation, the mazindol binding was not restored. Membranes that were pretreated with metaphit and washed had a lower density of mazindol binding sites than control membranes; the remaining mazindol sites had the same afinity for [3H]mazindol. These findings are in agreement with the previous studies on [3H]cocaine and [3H]methylphenidate binding. The following observations support that metaphit is irreversibly acting and not slowly dissociating from the mazindol recognition sites of the dopamine uptake carrier complex: (1) Metaphit did not change the off‐rate of [3H]mazindol binding, arguing against an allosteric action at a distinct site. (2) The presence of cocaine protected the mazindol binding sites from the action of metaphit, supporting binding of metaphit and mazindol to the same site. (3) Nine hours after metaphit pretreatment and removal, the degree of inhibition of mazindol binding was the same as immediately after pretreatment, consonant with an irreversible effect of metaphit. (4) The potency of metaphit in inhibiting mazindol binding was greater under slightly alkaline conditions, consistent with acylation of the mazindol sites. Furthermore, it was found that intracerebroventricular application of metaphit did not result in a decrease in the binding of [3H]mazindol 5 hr after the administration.
Review: Fine structure of synaptogenesis in the vertebrate central nervous system
Authors: Vaughn James E.
Published: January 2005

This article reviews studies of the formation of synaptic junctions in the vertebrate central nervous system. It is focused on electron microscopic investigations of synaptogenesis, although insights from other disciplines are interwoven where appropriate, as part of the review is concerned with the morphological maturation of synapses as described from both qualitative and quantitative perspectives. Next, epigenetic influences on synaptogenesis are examined, and later in the article the concept of epigenesis is integrated with that of hierarchy. It is suggested that the formation of synaptic junctions may take place as an ordered progression of epigenetically modulated events wherein each level of cellular affinity becomes subordinate to the one that follows. The ultimate determination of whether a synapse is maintained, modified or dissolved would be made by the changing molecular fabric of its junctional membranes. In closing, a hypothetical model of synaptogenesis is proposed, and an hierarchial order of events is associated with a speculative synaptogenic sequence. Key elements of this hypothesis are (1) epigenetic factors that facilitate generally appropriate interactions between neurites; (2) independent expression of surface specializations that contain sufficient information for establishing threshold recognition between interacting neurites; (3) exchange of molecular information that biases the course of subsequent junctional differentiation and ultimately results in (4) the stabilization of synaptic junctions into functional connectivity patterns.
Immunochemical identification of desmin in Torpedo postsynaptic membranes and at the rat neuromuscular junction
Authors: Sealock Robert , Murnane Amy A. , Paulin Denise , Froehner Stanley C.
Published: January 2005

Preparations of acetylcholine receptor‐rich (AChR‐rich) postsynaptic membranes from electric tissue of electric rays often contain an Mr 55,000 protein (55kD protein) that has not been previously characterized. Using a monoclonal antibody (MAb 1403) against the 55kD protein from Torpedo californica and a pan‐specific, anti‐intermediate filament antibody (Pruss et al., 1981; Cell 27:419–428), we show that the 55kD protein has the properties expected of Torpedo desmin. By the electron microscope immunogold method applied to perfusion‐fixed electric tissue, MAb 1403 labeled only cytoplasmic filaments in the electroplax. These filaments were neither more concentrated nor arranged detectably differently in postsynaptic regions relative to nonpostsynaptic regions. The 55kD protein could also be fractionated away from isolated postsynaptic membranes by gradient centrifugation. The protein is thus a minor component of the postsynaptic membrane in situ and after isolation. On semithin cryosections of rat skeletal muscle, on the other hand, MAb 1403, which recognizes rat desmin but not rat vimentin, gave strong fluorescent labeling of the postsynaptic region, weaker labeling of the Z‐line, and still weaker labeling of the cell surface immediately surrounding extrajunctional nuclei. The pattern of postsynaptic labeling suggests that desmin, presumably in the form of intermediate filaments, occurs near the AChR‐rich crests of the junctional folds, but is particularly concentrated among and around the ends of the folds. Similar results were obtained with a second monoclonal antibody raised against authentic desmin. These results suggest that desmin intermediate filaments may have an important role in organization of the postsynaptic cytoplasm in rat muscle.
Presence of calcium/calmodulin‐dependent protein Kinase II in Nerve terminals of rat brain
Authors: Walaas S. Ivar , Gorelick Fred S. , Greengard Paul
Published: January 2005

Calcium/calmodulin‐dependent protein kinase type II, a multimeric 550‐650 kilodalton enzyme composed of major alpha (50 kilodalton) and beta/beta' (60/58 kilodalton) subunits, is present in high concentrations in mammalian brain. Previous immunocytochemical studies indicated that the enzyme is enriched in cell bodies and dendrites, but did not show a clear‐cut localization in nerve terminals. The present study present evidence, using lesion‐induced degenerations of pre‐ and postsynaptic neuronal populations in the neostriatum and substantia nigra, that calcium/calmodulin‐dependent protein kinase II, as measured both by autophosphorylation of enzyme subunits and by synapsin I kinase activity, is present in high concentrations in several populations of presynaptic terminals. Lesions of the corticostriatal tract decreased the amount of enzyme by 30‐40% in the neostriatum, a decrease similar to that seen in the same region of synapsin I, a general nerve terminal market. Lesions of the striatonigral tract induced an even more pronounced decrease of the enzyme in the substantia nigra; this decrease was larger than the lesion‐induced change of synapsin I seen in the same region. Our data therefore indicate that certain nerve terminal population in the rat brain contain high levels of calcium/calmodulin‐dependent protein kinase II.
Phencyclidine and sigma receptors in rat spinal cord: Binding characterization and quantitative autoradiography
Authors: Aanonsen Linda M. , Seybold Virginia S.
Published: January 2005

These experiments were designed to compare phencyclidine (PCP) and s̀ (sigma) receptor binding sites in the rat spinal cord by using receptor binding and autoradiographic techniques. Binding sites for 3H‐TCP (3H‐1‐[1‐(2‐thienyl)cyclohexy]piperidine), a PCP receptor agonist, and (+)3H‐3‐PPP (3H‐(+)‐3‐(3‐hydroxyphenyl)‐N‐(1‐propyl)piperidine), a s̀ receptor agonist, in the rat spinal cord were shown to represent two populations of recognition sites. Inhibition studies revealed that ligands with high affinity for the PCP receptor (MK‐801 and PCP) were potent competitors at 3H‐TCP binding sites whereas the putative s̀ receptor ligands (±)pentazocine and haloperidol were potent competitors at (+)3H‐3‐PPP binding sites. The autoradiographic distribution of 3H‐TCP and (+)3H‐3‐PPP binding sites in adjacent sections of rat spinal cord demonstrated the occurrence of two distinct populations of binding sites. 3H‐TCP binding sites were localized primarily in laminae I and II in cervical and thoracic spinal segments. Binding sites in lamina I decreased in density along a rostral to caudal gradient in the spinal cord. The highest density of (+)3H‐3‐PPP binding sites was found in the ventral horn (lamina VIII and IX) and over perikarya in dorsal root ganglia. Significantly elevated densities of (+)3H‐3‐PPP binding sites were also found in lamina X within thoracic and lumbar segments and in the intermediolateral cell column. The results of the present study show that PCP and s̀ receptor binding sites are differentially localized in the rat spinal cord and suggest that separate binding sites exist for PCP and s̀ agonists.