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Dendritic Segments (dendritic + segment)
Selected AbstractsSynthesis and self-organization of rod,dendron and dendron,rod,dendron moleculesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2003Sébastien Lecommandoux Abstract We synthesized molecules containing one or two dendritic segments and a rigid-rod-like segment with their structures in the solid state. The molecules with rod,dendron or dendron,rod,dendron architecture had biphenyl ester rigid segments and 3,4,5 tris(n -dodecyloxy)benzoate of first or second generation as their dendritic segments. The variables investigated included the rod segment length as well as dendron generation, and all materials obtained were characterized by optical microscopy, differential scanning calorimetry, and X-ray scattering. Depending on the size of the rod segment and generation number of the dendritic segment, molecules organized into smectic, columnar, or cubic phases, and the symmetries observed were dominated by the anisotropic rod,rod interactions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3501,3518, 2003 [source] Dynamics of action potential backpropagation in basal dendrites of prefrontal cortical pyramidal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2008Wen-Liang Zhou Abstract Basal dendrites of neocortical pyramidal neurons are relatively short and directly attached to the cell body. This allows electrical signals arising in basal dendrites to strongly influence the neuronal output. Likewise, somatic action potentials (APs) should readily propagate back into the basilar dendritic tree to influence synaptic plasticity. Two recent studies, however, determined that sodium APs are severely attenuated in basal dendrites of cortical pyramidal cells, so that they completely fail in distal dendritic segments. Here we used the latest improvements in the voltage-sensitive dye imaging technique (Zhou et al., 2007) to study AP backpropagation in basal dendrites of layer 5 pyramidal neurons of the rat prefrontal cortex. With a signal-to-noise ratio of >,15 and minimal temporal averaging (only four sweeps) we were able to sample AP waveforms from the very last segments of individual dendritic branches (dendritic tips). We found that in short- (< 150 µm) and medium (150,200 µm in length)-range basal dendrites APs backpropagated with modest changes in AP half-width or AP rise-time. The lack of substantial changes in AP shape and dynamics of rise is inconsistent with the AP-failure model. The lack of substantial amplitude boosting of the third AP in the high-frequency burst also suggests that in short- and medium-range basal dendrites backpropagating APs were not severely attenuated. Our results show that the AP-failure concept does not apply in all basal dendrites of the rat prefrontal cortex. The majority of synaptic contacts in the basilar dendritic tree actually received significant AP-associated electrical and calcium transients. [source] Distribution and regulation of L-type calcium channels in deep dorsal horn neurons after sciatic nerve injury in ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005E. Dobremez Abstract Deep dorsal horn neurons are involved in the processing of nociceptive information in the spinal cord. Previous studies revealed a role of the intrinsic bioelectrical properties (plateau potentials) of deep dorsal horn neuron in neuronal hyperexcitability, indicating their function in pain sensitization. These properties were considered to rely on L -type calcium currents. Two different isotypes of L -type calcium channel alpha 1 subunit have been cloned (CaV1.2 and CaV1.3). Both are known to be expressed in the spinal cord. However, no data were available on their subcellular localization. Moreover, possible changes in CaV1.2 and CaV1.3 expression had never been investigated in nerve injury models. Our study provides evidence for a differential expression of CaV1.2 and CaV1.3 subunits in the somato-dendritic compartment of deep dorsal horn neurons. CaV1.2 immunoreactivity is restricted to the soma and proximal dendrites whereas CaV1.3 immunoreactivity is found in the whole somato-dendritic compartment, up to distal dendritic segments. Moreover, these specific immunoreactive patterns are also found in electrophysiologically identified deep dorsal horn neurons expressing plateau potentials. After nerve injury, namely total axotomy or partial nerve ligation, CaV1.2 and CaV1.3 expression undergo differential changes, showing up- and down-regulation, respectively, both at the protein and at the mRNA levels. Taken together, our data support the role of L-type calcium channels in the control of intrinsic biolectrical regenerative properties. Furthermore, CaV1.2 and CaV1.3 subunits may have distinct and specific roles in sensory processing in the dorsal horn of the spinal cord, the former being most likely involved in long-term changes after nerve injury. [source] Synthesis and self-organization of rod,dendron and dendron,rod,dendron moleculesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2003Sébastien Lecommandoux Abstract We synthesized molecules containing one or two dendritic segments and a rigid-rod-like segment with their structures in the solid state. The molecules with rod,dendron or dendron,rod,dendron architecture had biphenyl ester rigid segments and 3,4,5 tris(n -dodecyloxy)benzoate of first or second generation as their dendritic segments. The variables investigated included the rod segment length as well as dendron generation, and all materials obtained were characterized by optical microscopy, differential scanning calorimetry, and X-ray scattering. Depending on the size of the rod segment and generation number of the dendritic segment, molecules organized into smectic, columnar, or cubic phases, and the symmetries observed were dominated by the anisotropic rod,rod interactions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3501,3518, 2003 [source] A model of thalamocortical relay cellsTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Paul A. Rhodes It is well established that the main intrinsic electrophysiological properties of thalamocortical relay cells, production of a low threshold burst upon release from hyperpolarized potential and production of a train of single spikes following stimulation from depolarized potentials, can be readily modelled using a single compartment. There is, however, another less well explored intrinsic electrophysiological characteristic of relay cells for which models have not yet accounted: at somatic potentials near spike threshold, relay cells produce a fast ragged high threshold oscillation in somatic voltage. Optical [Ca2+] imaging and pharmacological tests indicate that this oscillation correlates with a high threshold Ca2+ current in the dendrites. Here we present the development of a new compartment model of the thalamic relay cell guided by the simultaneous constraints that it must produce the familiar regular spiking relay mode and low threshold rebound bursts which characterize these cells, as well as the less-studied fast oscillation occurring at near-threshold somatic potentials. We arrive at a model cell which is capable of the production of isolated high threshold Ca2+ spikes in distal branch segments, driven by a rapidly inactivating intermediate threshold Ca2+ channel. Further, the model produces the low threshold spike behaviour of the relay cell without requiring high T-current density in the distal dendritic segments. The results thus support a new picture of the dendritic tree of relay cells which may have implications for the manner in which thalamic relay cells integrate descending input from the cortex. [source] | ||||||||||