Housing under the pyramid reduces susceptibility of hippocampal CA3 pyramidal neurons to prenatal stress in the developing rat offspring.

Mother-offspring interaction begins before birth. The foetus is particularly vulnerable to environmental insults and stress. The body responds by releasing excess of the stress hormone cortisol, which acts on glucocorticoid receptors. Hippocampus in the brain is rich in glucocorticoid receptors and therefore susceptible to stress. The stress effects are reduced when the animals are placed under a model wooden pyramid. The present study was to first explore the effects of prenatal restraint-stress on the plasma corticosterone levels and the dendritic arborisation of CA3 pyramidal neurons in the hippocampus of the offspring. Further, to test whether the pyramid environment would alter these effects, as housing under a pyramid is known to reduce the stress effects, pregnant Sprague Dawley rats were restrained for 9 h per day from gestation day 7 until parturition in a wire-mesh restrainer. Plasma corticosterone levels were found to be significantly increased. In addition, there was a significant reduction in the apical and the basal total dendritic branching points and intersections of the CA3 hippocampal pyramidal neurons. The results thus suggest that, housing in the pyramid dramatically reduces prenatal stress effects in rats.

Relationships between dendritic morphology, spatial distribution and firing patterns in rat layer 1 neurons

The cortical layer 1 contains mainly small interneurons, which have traditionally been classified according to their axonal morphology. The dendritic morphology of these cells, however, has received little attention and remains ill defined. Very little is known about how the dendritic morphology and spatial distribution of these cells may relate to functional neuronal properties. We used biocytin labeling and whole cell patch clamp recordings, associated with digital reconstruction and quantitative morphological analysis, to assess correlations between dendritic morphology, spatial distribution and membrane properties of rat layer 1 neurons. A total of 106 cells were recorded, labeled and subjected to morphological analysis. Based on the quantitative patterns of their dendritic arbor, cells were divided into four major morphotypes: horizontal, radial, ascendant, and descendant cells. Descendant cells exhibited a highly distinct spatial distribution in relation to other morphotypes, suggesting that they may have a distinct function in these cortical circuits. A significant difference was also found in the distribution of firing patterns between each morphotype and between the neuronal populations of each sublayer. Passive membrane properties were, however, statistically homogeneous among all subgroups. We speculate that the differences observed in active membrane properties might be related to differences in the synaptic input of specific types of afferent fibers and to differences in the computational roles of each morphotype in layer 1 circuits. Our findings provide new insights into dendritic morphology and neuronal spatial distribution in layer 1 circuits, indicating that variations in these properties may be correlated with distinct physiological functions.

Location matters: the endoplasmic reticulum and protein trafficking in dendrites

Neurons are highly polarized, but the trafficking mechanisms that operate in these cells and the topological organization of their secretory organelles are still poorly understood. Particularly incipient is our knowledge of the role of the neuronal endoplasmic reticulum. Here we review the current understanding of the endoplasmic reticulum in neurons, its structure, composition, dendritic distribution and dynamics. We also focus on the trafficking of proteins through the dendritic endoplasmic reticulum, emphasizing the relevance of transport, retention, assembly of multi-subunit protein complexes and export. We additionally discuss the roles of the dendritic endoplasmic reticulum in synaptic plasticity.

Supramolecular effects in dentritic systems containing photoactive groups

In this article are described dendritic structures containing photoactive groups at the surface or in the core. The observed supramolecular effects can be attributed to the nature of the photoactive group and their location in the dendritic architecture. The peripheric azobenzene groups in these dendrimeric compounds can be regarded as single residues that retain the spectroscopic and photochemical properties of free azobenzene moiety. The E and Z forms of higher generation dendrimer, functionalized with azobenzene groups, show different host ability towards eosin dye, suggesting the possibility of using such dendrimer in photocontrolled host-guest systems. The photophysical properties of many dendritic-bipyridine ruthenium complexes have been investigated. Particularly in aerated medium more intense emission and a longer excited-state lifetime are observed as compared to the parent unsubstituted bipyridine ruthenium complexes. These differences can be attributed to a shielding effect towards dioxygen quenching originated by the dendritic branches

Subcellular localization of neurotrophins and neurotrophin receptors: implications for synaptic plasticity

A growing body of recent evidence indicate that neurotrophins can act as mediators of neuronal plasticity. In the context of a more detailed, comprehensive understanding of the function of neurotrophins it is essential to characterize where neurotrophins are synthesised and stored and from where they are released. Here we present evidence that the mRNAs for NGF, trkB and BDNF but not trkA are localised in the dendrites of rat neurons, thus implying that neurotrophins and their receptors can be synthesised at locations close to their sites of function, with particular regard to the dendritic synapses. The significance of this finding and its possible implications for synaptic plasticity are discussed within the theoretical framework of the synapse-specific control of individual synapses of a given neuron.

Plasticity of hippocampal and motor cortical pyramidal neurons induced by self-stimulation experience.

The self-stimulation (SS) induced neuronal plasticity was observed in CA3 hippocampal and layer V motor cortical pyramidal neurons. SS experience was allowed daily for a total of 1 hour for 10 days through four bipolar electrodes implanted bilaterally in lateral hypothalamus (LH) and substantia nigra-ventral tegmental area (SN-VTA) in adult male Wistar rats. Examination of pyramidal neurons stained by rapid Golgi technique was made in a total of 1,600 neurons out of 80 rats consisting of 4 groups. The dendritic intersections were quantified upto 200 and 120 microns radial distances in apical and basal dendrites respectively. The CA3 hippocampal and layer V motor cortical pyramidal neurons of SS group revealed significant increase (P < 0.001, two-way ANOVA) in dendritic intersections in both apical and basal dendrites, compared to normal control (NC), sham control (SH) and experimenter-administered (EA) group of animals. These results demonstrate that SS experience promotes increase in dendritic length in hippocampal and motor cortical pyramidal neurons.

Specificity of synapse formation in the cockroach

Las conecciones sinápticas entre las neuronas sensoriales de los pelos filiformes (FHSNs) y las interneuronas gigantes (GIs) en el ganglio terminal abdominal del primer estadió ninfal de la cucaracha Periplaneta americana han sido utilizado como sistema modelo para investigar los mecanismos de especificidad en la formación de sinapsis. Técnicas de electrofisiología y microscopía electrónica fueron usadas con el fin de establecer los circuitos normales de conección entre FHSNs y GIs. Se encontró que durante el período de "sinaptogénesis" no hubo equivocación al formarse las sinápsis entre los axones sensoriales y las dendritas de las interneuronas correspondientes. Estudios con un mutante que posee un axon sensorial adicional han arrojado nueva luz sobre la función de la información posicional para determinar la forma y las conecciones de la neurona sensorial con las GIs. Ha sido obtenida evidencia electrofisiológica de interacciones competitivas entre el axon sensorial adicional y el original

Aminoacids and oscillatory electrocortical activity

En la corteza intacta y en islotes aislados de la misma corteza de gastos anestesiados con pentobarbital se estudiaron algunos de los efectos de la aplicación local de diversos aminoácidos: glutamato, aspartato, glicina, GABA y alanina. Tambien se hicieron observaciones semejantes en la corteza expuesta de la tortuga de tierra, anestesiada con el mismo barbitúrico. La capacidad de los aminoácidos para favorecer la producción de respuestas repetitivas fue confirmada. Esta capacidad tambien fue observada en la corteza aislada. A menudo ocurrió una actividad oscilatoria que se presentó al parecer espontáneamente, o bajo la acción de los aminoácidos, o inducida por las espigas de estricnina inducida, o por alguna otra onda de potencial de amplitud relativamente grande. En ocasiones fue observado que las ondas sucesivas de los potenciales oscilantes aparecían separadas por escalones. Un retardo semejante fue observado entre la RCD y la espiga de estricnina inducida por ésta. Las oscilaciones fueron de frecuencias diferentes, pero dentro de los límites que se observan para los potenciales en los husos de sueño. También se presentaron estas oscilaciones en la corteza aislada. La negatividad inicial de la respuesta cortical directa mostró mayor resistencia que el componente negativo de las espigas de estricnina inducida a la acción depresora de los aminoácidos. Durante los efectos de estas sustancias la impedancia eléctrica de la corteza mostró cierto aumento. Esta evidencia se desprende de las medidas directas hechas algunas veces de esta impedancia, así como de otras observaciones menos directas como son: el aumento en la amplitud de los artefactos del estímulo para choques de igual intensidad, y la disminución de la corriente medida cuando fue aplicado un pulso largo de corriente directa subumbral a través de los electrodos de estimulación. Se discuten los mecanismos posibles de los efectos estudiados de los aminoácidos...