The Anterior Insula and its Projection to the Prelimbic Cortex are Involved in the Regulation of 5-HT-Induced Itch / 神经科学通报·英文版

Itch is an unpleasant sensation that urges people and animals to scratch. Neuroimaging studies on itch have yielded extensive correlations with diverse cortical and subcortical regions, including the insular lobe. However, the role and functional specificity of the insular cortex (IC) and its subdivisions in itch mediation remains unclear. Here, we demonstrated by immunohistochemistry and fiber photometry tests, that neurons in both the anterior insular cortex (AIC) and the posterior insular cortex (PIC) are activated during acute itch processes. Pharmacogenetic experiments revealed that nonselective inhibition of global AIC neurons, or selective inhibition of the activity of glutaminergic neurons in the AIC, reduced the scratching behaviors induced by intradermal injection of 5-hydroxytryptamine (5-HT), but not those induced by compound 48/80. However, both nonselective inhibition of global PIC neurons and selective inhibition of glutaminergic neurons in the PIC failed to affect the itching-scratching behaviors induced by either 5-HT or compound 48/80. In addition, pharmacogenetic inhibition of AIC glutaminergic neurons effectively blocked itch-associated conditioned place aversion behavior, and inhibition of AIC glutaminergic neurons projecting to the prelimbic cortex significantly suppressed 5-HT-evoked scratching. These findings provide preliminary evidence that the AIC is involved, at least partially via aversive emotion mediation, in the regulation of 5-HT-, but not compound 48/80-induced itch.

A modified intracellular labelling technique for high-resolution staining of neuron in 500 microm-thickness brain slice / 中国应用生理学杂志

<p><b>AIM</b>To develop simple but reliable intracellular labelling method for high-resolution visualization of the fine structure of single neurons in brain slice with thickness of 500 microm.</p><p><b>METHODS</b>Biocytin was introduced into neurons in 500 microm-thickness brain slices while blind whole cell recording. Following processed for histochemistry using the avidin-biotin-complex method, stained slices were mounted in glycerol on special glass slides. Labelled cells were digital photomicrographed every 30 microm and reconstructed with Adobe Photoshop software.</p><p><b>RESULTS</b>After histochemistry, limited background staining was produced. The resolution was so high that fine structure, including branching, termination of individual axons and even spines of neurons could be identified in exquisite detail with optic microscope. With the help of software, the neurons of interest could be reconstructed from a stack of photomicrographs.</p><p><b>CONCLUSION</b>The modified method provides an easy and reliable approach to revealing the detailed morphological properties of single neurons in 500 microm-thickness brain slice. Without requisition of special equipment, it is suited to be broadly applied.</p>

A comparison of the spontaneous firing patterns between principal cells and fast spiking interneurons from dentate gyrus in waking guinea pigs / 神经科学通报·英文版

Objective To explore the possible mechanisms that cause the dentate gyrus (DG) neurons to play different roles in information coding. Methods In vivo extracellular single unit recording was performed on 22 waking female guinea pigs, which were positioned in a sound-attenuated recording chamber without any muscular relaxants. The spontaneous firing patterns of the DG neurons were detected and compared. Results There were two different electrophysiological populations in the DG of guinea pigs, principal cells (PCs) and fast spiking interneurons (INs). Of the PCs, 1.3% discharged regularly, 48.1% irregularly and 50.6% in bursts; in contrast, of the INs units, 64.1% discharged regularly, 2.6% irregularly and 33.3 % in bursts. The spontaneous firing patterns of PCs were significantly different from those of INs (P <0.01). In addition, the differences of several interspike interval (ISI) parameters also have been observed: (1) the ISI coefficients of variation of PCs (3.39 +/- 3.56) were significantly higher than those of INs (1.08 +/- 0.46) (P < 0.01 ); (2) the ISI asymmetric indexes of PCs (0. 047 +/- 0. 059) were significantly lower than those of INs (0. 569 +/-0. 238) (P < 0.01). Conclusion In the DG, the spontaneous firing patterns of PCs were significantly different from those of INs. The former were prone to fire in bursts, the latter were prone to fire regularly. The different roles in information coding between PCs and INs might be caused by their different firing patterns.

Spontaneous discharges of pyramidal cells in the dorsal hippocampus of guinea pig / 生理学报

To determine the characteristics of spontaneous discharges of hippocampal pyramidal cells (PCs), extracellular neuronal firing in CA1 and CA3 regions of dorsal hippocampus was recorded, the firing modes and interspike interval (ISI) were analyzed with the conventional and nonlinear methods. PCs were discriminated from interneurons using the measurement of action-potential duration and firing rate in this study. There was no significant difference in duration, mean firing frequency, complexity and firing mode between the neurons in CA1 and CA3 regions both in anesthetized and awake animals. The complexity of neurons was higher in awake group than that in anesthetized group, though no difference was found in firing rate. There were differences in the type of pyramidal cells and the coefficient of variance of ISI of neurons. The results obtained from the spontaneous discharges of dorsal hippocampal pyramidal cells reveal some nonlinear and linear aspects in anesthetized and awake states. It seems likely that the combination of conventional and non-linear measurements of the hippocampal pyramidal cells encoding may reflect genuine characteristics of the hippocampal pyramidal cells.

Effects of acute hypobaric hypoxia on spatial learning, memory and its relationship with orphanin FQ of hippocampus in rats / 中国应用生理学杂志

<p><b>AIM</b>To study the relationship between changes of learning, memory and orphanin FQ (OFQ) in hippocampus of rats in acute hypobaric hypoxia at two different altitude levels of 4 500 m(moderate) and 7 500 m(serious).</p><p><b>METHODS</b>Hypobaric chamber, Morris water maze training method and RT-PCR technique were used in the experiment.</p><p><b>RESULTS</b>(1) Compared with the control, the OFQ mRNA expression of hippocampus increased significantly after exposure to acute serious hypobaric hypoxia (8 h/d for 6 d in succession), but obviously decreased after Morris water maze training (6 times/d for 6 d in succession, the latency of place navigation was shortened). (2) After exposure to acute hypobaric hypoxia, the latency of place navigation was markedly elongated, but the OFQ mRNA of hippocampus was significantly higher than that of learning and memory group.</p><p><b>CONCLUSION</b>The hippocampal OFQ was involved in the mechanism of decrease in spatial learning and memory induced by acute hypobaric hypoxia.</p>