bluuebunny/crossref_metadata_2025_split huggingface dataset:
Muscarinic Receptor Characteristics and Regulation in Rat Cerebral Cortex: Changes during Development, Aging and the Oestrous Cycle
Authors: van Huizen Frans , March Derrick , Cynader Max S. , Shaw Christopher 
Published: April 2006

AbstractThe effects of postnatal development, aging and the oestrous cycle on muscarinic acetylcholine receptor (mAChR) properties were examined in in vitro living slices of rat neocortex. Using the hydrophilic antagonist ([3H]NMS) to label cell surface mAChRs, an increase in both Bmax and Kd was found during the first postnatal weeks. These values peaked at between 20–40 days postnatally and then declined to adult levels. After 3 months of age, a steady decline in receptor number started: it was 10.1% lower at 10 months and 38.7% lower at 17 months of age. In contrast, Kd values increased, being 31.7 and 20% higher respectively at these ages. Carbachol‐induced (4 h at 37°C) down‐regulation of receptor number was ‐22.2% in newborn and 26.1% in adult (3‐month‐old) rats, but only 16.3% at 20–40 days of age. The degree of carbachol‐induced down‐regulation of mAChR was not affected in the older animals. Veratridine, which increases neural activity, also induced a significant reduction in [3H]NMS binding sites of 11.4% in rats aged 0–20 days and 22.4% in 3‐month‐old rats, but at 20–40 and 40–60 days of age no significant down‐regulation of receptor number was observed. Furthermore, down‐regulation was absent in the 10‐month‐old rats as well. Since a great variation in Smax and Kd values was seen in 3‐month‐old females but not in male rats, we investigated mAChR characteristics during the oestrous cycle of female rats. In pro‐oestrus, mACh receptor number was increased and affinity decreased in comparison with di‐oestrus. The transition from pro‐oestrus into oestrus was accompanied by a significant decrease in receptor number and an increase in receptor affinity. Injection of ovariectomized females with oestradiol and progesterone induced an increase in the number of binding sites and a decrease in affinity. These values are comparable to those seen in pro‐oestrous rats. These results demonstrate (i) that both carbachol‐ and veratridine‐induced down‐regulation of the mACh receptor is limited during the critical period of cortical plasticity, (ii) that after 3 months of age mACh receptor number is gradually declining, and (iii) that the steroid hormones oestrogen and progesterone are capable of modifying the characteristics of muscarinic antagonist binding sites in the female rat cerebral cortex.
Fibroblast Growth Factor‐5 Promotes Differentiation of Cultured Rat Septal Cholinergic and Raphe Serotonergic Neurons: Comparison with the Effects of Neurotrophins
Authors: Lindholm Dan , Hartikka Jukka , da Penha Berzaghi Maria , Castrén Eero , Tzimagiorgis Georgios , Hughes Richard A. , Thoenen Hans 
Published: April 2006

AbstractFibroblast growth factor‐5 (FGF‐5) is a member of the fibroblast growth factor gene family, which has a signal sequence characteristic of secretory proteins. FGF‐5 mRNA has previously been shown to be present in the adult mouse brain. Here we demonstrate that recombinant FGF‐5 has neurotrophic activity on cultured rat septal cholinergic and raphe serotonergic neurons. The effect of FGF‐5 on serotonin uptake was stronger than that evoked with either brain‐derived neurotrophic factor or neurotrophin‐3. FGF‐5 also increased the choline acetyltransferase activity of cultured rat septal cholinergic neurons, the effect being additive to that of nerve growth factor. In situ hybridization experiments and immunohistochemistry using a specific anti‐FGF‐5 antibody demonstrated that FGF‐5 is expressed in rat hippocampal neurons. Like nerve growth factor mRNA, the levels of FGF‐5 mRNA in the rat hippocampus increased substantially during early postnatal development. In addition, injection of the muscarinic receptor agonist pilocarpine elevated FGF‐5 mRNA. The presence of the secretory FGF‐5 in the rat hippocampus, a target field of septal cholinergic and raphe serotonergic neurons, suggests that FGF‐5 acts as a trophic factor for these neurons also in vivo.
Development of the Thalamic Reticular Nucleus in Ferrets with Special Reference to the Perigeniculate and Perireticular Cell Groups
Authors: Mitrofanis John 
Published: April 2006

AbstractThis study describes the development of the ferret thalamic reticular nucleus from Nissl‐stained and from parvalbumin‐immunostained sections. From early stages [embryonic day (E) 23‐E25], there is a large group of ventral thalamic cells which lies between the dorsal thalamus and the primordial internal capsule. This group of cells, the primordial reticular nucleus, gives rise to the main body of the reticular nucleus, the perigeniculate nucleus and the perireticular nucleus. In the reticular nucleus, there are two waves of parvalbumin expression during development. The first wave begins prenatally in small cells which are seen rarely after birth. Their fate is not clear: they may have lost immunoreactivity, migrated elsewhere, or died. At the end of the first wave, a second wave begins in a distinct group of larger ovoid reticular cells, which appear to remain into adulthood. At about birth, the dorsocaudal pole of the reticular nucleus first forms the perigeniculate nucleus. During this developmental stage, cells which make up the reticular and perigeniculate nuclei are the only parvalbumin‐immunostained structures in the thalamus. Thus, rather than develop from the dorsal thalamus, the perigeniculate nucleus seems to have its origins in the ventral thalamus together with the reticular nucleus. During development, the reticular nucleus is associated closely with a large mass of cells located in the internal capsule, called the perireticular nucleus. Later, the perireticular nucleus is dramatically reduced in size: that is, there is a large reduction in the number of perireticular cells seen per section and in the extent of the nucleus across the internal capsule. There are two cytoarchitectonically distinct groups of perireticular cells. One group of cells, called the large‐celled perireticular zone (LPR), enters the internal capsule from early prenatal development (E25). Many of these cells reach the globus pallidus and extend as far as the cortical subplate zone. The LPR together with the subplate form an extensive neuronal network in the white matter during early development, which disappears later in development (about postnatal day 20). The second group of perireticular cells is made up of smaller cells and is called the small‐celled perireticular zone (SPR). These small cells enter the internal capsule from the reticular nucleus just prior to birth. Many of the cells in the SPR remain in the adult.
Innervation of Putative Rapidly Adapting Mechanoreceptors by Calbindin‐ and Calretinin‐immunoreactive Primary Sensory Neurons in the Rat
Authors: Duc Christophe , Barakat‐Walter Ibtissam , Droz Bernard 
Published: April 2006

AbstractCalbindin and calretinin are two homologous calcium‐binding proteins that are expressed by subpopulations of primary sensory neurons. In the present work, we have studied the distribution of the neurons expressing calbindin and calretinin in dorsal root ganglia of the rat and their peripheral projections. Calbindin and calretinin immunoreactivities were expressed by subpopulations of large‐ and small‐sized primary sensory neurons and colocalized in a majority of large‐sized ones. The axons emerging from calbindin‐ or calretinin‐immunoreactive neurons innervated muscle spindles, Pacini corpuscles and subepidermal lamellar corpuscles in the glabrous skin, formed palisades of lanceolate endings around hairs and vibrissae, and gave rise to intraepidermal nerve endings in the digital skin. Since most of these afferents are considered as rapidly adapting mechanoreceptors, it is concluded that calbindin‐ or calretinin‐expressing neurons innervate particular mechanoreceptors that display physiological characteristics of rapid adaptation to stimuli.
Evidence for Excitatory Amino Acid Neurotransmitters in Forward and Feedback Corticocortical Pathways within Rat Visual Cortex
Authors: Johnson Randall R. , Burkhalter Andreas 
Published: April 2006

AbstractIt is a commonly accepted notion that cells which make projections between the multiple cortical areas found in the mammalian visual system are excitatory, but there is little direct evidence that this is the case. Here we demonstrate using retrograde tracing with D‐[3H]aspartate that connections in the rat which project from lower to higher visual areas (i.e. forward) and those which project from higher to lower areas (i.e. feedback) may use excitatory amino acid neurotransmitters. Following injection into the primary visual cortex, clusters of retrogradely labelled cells were found in several extrastriate areas within the cytoarchitectonic subdivisions 18a (‘areas’ LM, AL, PX, FLX, RL, AX) and 18b (‘area’ MX), and in the retrosplenial cortex. In all of these areas D‐[3H]aspartate‐labelled cells were surrounded by diffuse label which may represent anterograde labelling of axon terminals. This suggests that both legs of reciprocal intracortical circuits have similar chemospecificity. To directly demonstrate excitatory amino acid localization in forward projections, D‐[3H]aspartate was injected into extrastriate area LM. As expected, the results revealed retrogradely labelled neurons within area 17. Outside area 17, LM injections labelled neurons in AL, PX, FLX, RL, AX and MX. Taken in the context of the hierarchy of areas in rat cerebral cortex (Coogan and Burkhalter, J. Neurosci., 13, 3749–3772, 1993), these results show that D‐[3H]aspartate labels: (1) forward connections from area 17 to LM, AL, PX, RL, AX and MX, (2) feedback connections from LM, AL, FLX, PX, RL, AX and MX to area 17, (3) feedback connections from AL, PX, RL, AX and MX to LM, and (4) lateral connections between FLX and LM. These findings strongly indicate that both forward and feedback connections as well as lateral connections at several different levels of the cortical hierarchy use excitatory amino acid neurotransmitters.
Chemical Compartmentation and Relationships between Calcium‐binding Protein Immunoreactivity and Layer‐specific Cortical and Caudate‐projecting Cells in the Anterior Intralaminar Nuclei of the Cat
Authors: Molinari M. , Leggio M. G. , Dell'Anna M. E. , Giannetti S. , Macchi G. 
Published: April 2006

AbstractNeurons projecting to the parietal cortex or striatum and neurons showing immunoreactivity for the calcium‐binding proteins parvalbumin and 28KD‐calbindin were examined in the anterior intralaminar nuclei (IL) of the cat. Retrograde tracing from deep or superficial parietal cortical layers or from the caudate nucleus was coupled with immunohistochemistry to determine which of these proteins were expressed in the projection neurons. It was found that IL neurons project to deep as well as to superficial layers of the parietal cortex, that IL‐cortical neurons could be differentiated into two populations according to their cortical projection pattern and their soma size, and that IL neurons projecting to the parietal cortex or to the striatum express 28KD calbindin immunoreactivity but not parvalbumin immunoreactivity. The distribution of immunoreactivity to 28KD calbindin and parvalbumin in the neuropil showed a consistent complementary distribution pattern in the IL. The compartments based on differential parvalbumin and 28KD calbindin expression may indicate the presence of functionally segregated units in IL.
Characteristics of Calcium Channels Responsible for Voltage‐activated Calcium Entry in Rat Cerebellar Granule Cells
Authors: Bossu J. L. , De Waard M. , Fagni L. , Tanzi F. , Feltz A. 
Published: April 2006

AbstractThe properties and characteristics of calcium channel openings in cerebellar granule cells were analysed by the cell‐attached patch‐clamp technique. At depolarized potentials, with 110 mM Ba2+ as the divalent charge carrier, 36% of the patches displayed activity that consisted of elementary events whose amplitude ranged from – 0.3 to –1. 75 pA at 0 mV, giving rise to a high threshold current. In this population of events at least four different types of channel openings were identified by their distinct biophysical and pharmacological properties. Two types of channel openings, with conductances around 24 and 7 pS, had similar characteristics in that both opened following two modes of gating characterized by brief (˜ 2 ms) and longer openings (˜ 8 ms) and both were sensitive to dihydropyridines. A further type of channel opening, with a conductance around 11 pS gated mainly with brief openings (∼1 ms), was shown to be insensitive to dihydropyridines but was undetectable in recordings from the cells that had been treated with ω‐conotoxin. The last type of event was revealed after treatment of the cell with nicardipine or nifedipine and ω‐conotoxin. The corresponding channel had a conductance of 19 pS and opened in one dominant mode characterized by brief openings (∼1 ms). The data obtained on single‐channel activity of cerebellar granule cells are compared with the properties of the total current recorded in whole‐cell conditions.
Effects of Transforming Growth Factor β1, on Scar Production in the Injured Central Nervous System of the Rat
Authors: Logan Ann , Berry Martin , Gonzalez Ana Maria , Frautschy Sally A. , Sporn Michael B. , Baird Andrew 
Published: April 2006

AbstractIn the central nervous system (CNS), nerve regeneration after traumatic injury fails. The formation of a dense fibrous scar is thought to restrict in part the growth of axonal projections, providing one of the many reasons that complete lesions of neural pathways in the adult mammalian CNS are rarely followed by significant functional recovery. In order to determine which mechanisms mediate scar formation in the CNS and to investigate whether they can be modulated in vivo, we have attempted to define the potential role of trophic factors. Our previous studies have shown the focal elevation of transforming growth factor β1 (TGFβ1) expression in lesioned CNS tissue. In the studies described here, we demonstrate that TGFβ1 participates in the scarring response in the rat brain. First, the elevated protein levels of TGFβ1 are localized to specific populations of injury‐responsive cells in the traumatized CNS. Furthermore, the injection of TGFβ1 into the brains of injured rats causes a dramatic increase in the scarring response. Conversely, when neutralizing TGFβ1 antibodies are administered, the deposition of fibrous scar tissue and the formation of a limiting glial membrane that borders the lesion is significantly attenuated, thus establishing a role for the endogenous growth factor in regulation of the non‐glial component of the scar. In implicating TGFβ1 in the scarring response in the CNS, the potential use for TGFβ1 antagonists as inhibitors of scar formation in the injured mammalian CNS is self‐evident.
Muscarinic Regulation of Ca2+ Currents in Rat Sensory Neurons: Channel and Receptor Types, Dose ‐ response Relationships and Cross‐talk Pathways
Authors: Wanke Enzo , Bianchi Laura , Mantegazza Massimo , Guatteo Ezia , Mancinelli Enzo , Ferroni Arnaldo 
Published: April 2006

AbstractWe studied, in rat sensory neurons, the modulation of high voltage‐activated Ca2+ currents (ICa mediated by the pertussis toxin‐sensitive activation of muscarinic receptors, which were found to be of subtypes M2, or M4. Muscarine reversibly blocked somatic Ca2+ spikes but strong predepolarizations only partially relieved the inhibited Ca2+ current. On the other hand, the putative coupling messenger could not rapidly diffuse towards channels whose activity was recorded from a macro‐patch. The perforated patch technique virtually prevented the response rundown present during whole‐cell experiments. Both ω‐conotoxin GVIA (ω‐CgTx)‐sensitive channels and ω‐CgTx‐ and dihydropyridine‐resistant channels are coupled to the muscarinic receptor, but not the L‐channel. When measured in the same neuron, dose ‐ response relationships for the first and subsequent agonist applications differed; maximal inhibition, the reciprocal of half‐maximal concentration and the Hill coefficient were always highest in the first trial. Muscarine and oxotremorine exhibited monotone dose ‐ response curves, but oxotremorine‐M showed non‐linear relationships which became monotonic when cells were intracellularly perfused with inhibitors of protein kinase A (PKA) and C (PKC), suggesting that either PKA or receptor‐induced PKC could phosphorylate and thus inactivate G‐proteins or other unknown proteins involved in inhibitory muscarinic actions on ICa. In summary, these data provide a preliminary pharmacological characterization of the muscarinic inhibition of the Ca2+ channels in sensory neurons, with implications about agonist specificity and the interplay between signalling pathways.
Intracellular Action of Spermine on Neuronal Ca2+ and K+ Currents
Authors: Drouin Herbert , Hermann Anton 
Published: April 2006

AbstractIntra‐and extracellular effects of the polyamine spermine on electrical activity and membrane currents of identified neurons in the abdominal ganglion of Aplysia californica were studied under current‐and voltage‐clamp conditions. Lonophoretic injection of spermine reduced the amplitude of action potentials and altered their time course as well as spontaneous discharge activity. Investigation of membrane currents showed that intracellular spermine suppressed the total outward current but increased the inward rectifier current. After separation of ion currents it was found that the voltage‐activated, delayed K+ outward current and the Ca2+ inward current were reduced by intracellular spermine in a dose‐ and voltage‐dependent manner. The block of the K+ current can be described by a voltage‐dependent reaction, where one spermine molecule binds to one channel. The binding constant Kb, at zero voltage, and the effective valency, zδ, had values of 176/M and 0.41 for cell R‐15, 223/M and 0.64 for cell L‐11, and 137/M and 0.42 for cell L‐3. Apparently, more than one spermine cation is needed to block one Ca2+ channel, since the coefficient n, which absorbs the molecularity and cooperativity of the reaction, had non‐integral values between 1.34 and 2.22. The binding constant Kb and the effective valency zδ had values of 265/M and 0.64 for cell R‐15, 821M and 0.56 for cell L‐4, and 263/M and 0.51 for cell L‐6. Intracellular spermine also blocked the Ca2+‐activated K+ current induced by ionophoretic Ca2+‐injections, but increased the current at prolonged times after spermine injection. Extracellular spermine had no effect on electrical activity or on membrane currents. The results indicate that intracellular spermine affects the electrical discharge activity of neurons by acting as a blocker and/or modulator at voltage‐dependent membrane conductances.
Different Domains of the F3 Neuronal Adhesion Molecule are Involved in Adhesion and Neurite Outgrowth Promotion
Authors: Durbec Pascale , Gennarini Gianfranco , Buttiglione Mara , Gomez Sophie , Rougon Geneviève 
Published: April 2006

AbstractThe mouse F3 cell surface protein is preferentially expressed on axons of subpopulations of neurons and is anchored to the membrane by a glycosyl‐phosphatidylinositol group. It consists of six immunoglobulin‐like domains and four fibronectin type III homologous repeats, and can be found both in membrane‐anchored and soluble forms. We have previously established that F3 fulfils the operational criteria of a cell adhesion molecule when anchored to the plasma membrane and that its soluble form stimulates neurite initiation and neurite outgrowth. To further characterize F3‐mediated adhesion and to investigate whether adhesion and neurite outgrowth promoting activities are displayed by different parts of the molecule, we (i) selected F3 transfected CHO cells expressing increasing levels of F3 at their surface and (ii) prepared transfectants expressing an F3 molecule with its fibronectin type III repeats deleted. We show that the F3 molecule mediates divalent‐cation‐independent, temperature‐dependent binding. The levels of aggregation of F3 transfectants are proportional to the level of F3 expression. Transfectants expressing F3 deleted of the fibronectin type Ill repeats lose their adhesive properties; conversely, cells expressing wild‐type F3 and treated with collagenase, specifically removing the immunoglobulin‐like domains, are still able to aggregate. Therefore, in this model adhesion site(s) mapped to the fibronectin type III repeats. By contrast, transfectants expressing deleted F3, as well as the soluble forms of this F3 deleted molecule, were able to stimulate neurite outgrowth of sensory neurons similarly to wild‐type F3. Our data indicate that F3 is a multifunctional molecule and that adhesion and neurite outgrowth promoting properties are expressed by distinct and independent domains.
Motor Neuron Death Induced by Axotomy in Neonatal Mice Occurs More Slowly in a Mutant Strain in Which Wallerian Degeneration is Very Slow
Authors: Lapper S. R. , Brown M. C. , Perry V. H. 
Published: April 2006

AbstractIn contrast to motor neurons of adults, motor neurons of neonatal mice die if their axons are cut. We have examined the extent, the time course and the loss of susceptibility with age to such induced death in C57BLWlds mice. This is a strain which has a dominant autosomal mutation which dramatically slows the rate of degeneration of axons separated from their cell bodies. Following axotomy in neonatal animals the total number of motor neurons killed is no less in C57BL/Wdls mice than in two other strains (C57BL/6J/Ola and BALB/c/Ola). Indeed, the susceptibility to axotomy persists to a later age in C57BL/Wlds mice. However, the rate of cell death is significantly slower than in the two other strains; in C57BL/Wlds mice under a week old at the time of sciatic nerve section only‐16% of motor neurons have been lost 3 days after axotomy, whereas in the other mice ‐45–84% of the final loss has by then occurred. This result extends previous work which showed that retrograde degeneration of retinal ganglion cells of adult mice was slower in C57BL/Wlds mice (V. H. Perry et al., Eur. J. Neurosci., 2, 408–413, 1991). It is therefore possible that Wallerian degeneration of axons shares features in common with retrograde nerve cell death and that the Wlds mutation may throw light on aspects of this complex process.
Expression of Neuronal Nicotinic Acetylcholine Receptor Subunit Genes in the Rat Autonomic Nervous System
Authors: Rust G. , Burgunder J.‐M. , Lauterburg T. E. , Cachelin A. B. 
Published: April 2006

AbstractIn the autonomic nervous system efferent signals are relayed in sympathetic and parasympathetic ganglia. Fast synaptic transmission between pre‐ and postsynaptic neurons is achieved by neuronal nicotinic acetylcholine receptors (nAChRs). There is still little known about the subunit composition of these receptors. Establishing the subunit composition of native neuronal nAChRs is important for the understanding of their functional properties both in vivo and after expression in heterologous expression systems. We have combined in situ hybridization and autoradiography to detect the presence of mRNAs encoding subunits of neuronal nAChRs in sympathetic and parasympathetic ganglia. Inspection of the autoradiographs showed that the hybridization signal of five riboprobes (α3, 014–1, α7, β2 and β4) was significantly higher than the unspecific signal obtained with sense riboprobes. The distribution of α7 was tissue‐dependent: a7 riboprobe binding was detected in the neurons of the superior cervical ganglion, adrenal medulla and ciliary ganglion. In contrast, the α7 hybridization signal was found only in a small fraction (1 ‐3%) of the neurons of the sphenopalatine and otic ganglia. Our results are consistent with the idea that α3 mRNA expression levels are somewhat higher than those of α7, α4 ‐1, β2 and β4.