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.

Estragole blocks neuronal excitability by direct inhibition of Na+ channels

Estragole is a volatile terpenoid, which occurs naturally as a constituent of the essential oils of many plants. It has several pharmacological and biological activities. The objective of the present study was to investigate the mechanism of action of estragole on neuronal excitability. Intact and dissociated dorsal root ganglion neurons of rats were used to record action potential and Na+ currents with intracellular and patch-clamp techniques, respectively. Estragole blocked the generation of action potentials in cells with or without inflexions on their descendant (repolarization) phase (Ninf and N0 neurons, respectively) in a concentration-dependent manner. The resting potentials and input resistances of Ninf and N0 cells were not altered by estragole (2, 4, and 6 mM). Estragole also inhibited total Na+ current and tetrodotoxin-resistant Na+ current in a concentration-dependent manner (IC50 of 3.2 and 3.6 mM, respectively). Kinetic analysis of Na+ current in the presence of 4 mM estragole showed a statistically significant reduction of fast and slow inactivation time constants, indicating an acceleration of the inactivation process. These data demonstrate that estragole blocks neuronal excitability by direct inhibition of Na+ channel conductance activation. This action of estragole is likely to be relevant to the understanding of the mechanisms of several pharmacological effects of this substance.

Prevalência de ansiedade e depressão e suas comorbidades em pacientes com doença renal crônica em hemodiálise e diálise peritoneal

Introdução: Os pacientes com doença renal crônica (DRC) que realizam terapia renal substitutiva (TRS) estão sujeitos a maior prevalência de distúrbios de humor. Objetivo: O objetivo do presente estudo é comparar a prevalência de ansiedade e depressão nos pacientes que realizam hemodiálise (HD) e diálise peritoneal (DP), levando em conta comorbidades que podem contribuir para isso. Métodos: O estudo foi realizado em Ponta Grossa, PR, com pacientes portadores de DRC, utilizando os inventários de depressão e ansiedade de Beck (BDI e BAI) e a Escala Hospitalar de Ansiedade e Depressão (EHAD). Resultados: Foram estudados 155 pacientes, 128 no grupo em HD e 27 em DP. No primeiro, depressão foi encontrada em 22,6% dos pacientes no BDI e em 9,3% na EHAD, e ansiedade em 25,7% no BAI e em 11,7% na EHAD. No grupo em DP, 29,6% dos pacientes apresentaram depressão no BDI e 14,8% na EHAD, e ansiedade em 11,1% no BAI e em nenhum na EHAD. Conclusão: A realização de hemodiálise ou diálise peritoneal não influenciou na prevalência de ansiedade ou depressão nos pacientes com DRC.