High-frequency stimulation on cell soma induces potentiation of intrinsic excitability in VTA dopaminergic neurons / 生理学报

Ventral tegmental area (VTA) is an important relay station of signal transmission in the reward system. The plasticity of VTA dopaminergic neurons directly influences actions of other regions of the reward system. Studies concerning the plasticity of VTA dopaminergic neurons focus mainly on synaptic plasticity, while much less attention has been given to the plasticity of intrinsic excitability of the neurons. The aim of the present study was to investigate the effect of high-frequency stimulation (HFS) on the plasticity of excitability of VTA neuron. Whole-cell patch-clamping was performed on VTA dopaminergic neurons in midbrain slices bathed with PTX, AP-5 and CNQX, and HFS was introduced to cell soma. The result showed that, after HFS induction the pharmacologically isolated neurons showed increased input resistance and firing frequency, as well as decreased rheobase. Meanwhile, the steady-state whole-cell current decreased, and the hyperpolarization-activated current (I(h)) decreased. These results suggest that HFS on soma induces a long-term potentiation of excitability in VTA dopaminergic neurons, and the underlying mechanism involves the changes of membrane current.

Phenotype of congenital cataract accompanied with iris dysplasia / 中华实验眼科杂志

Background Certain relationship has been found between phenotype and genes mutation of congenital cataract.It is clear that different genetic mutations can cause the same complication in congenital cataract,meanwhile,different complications may be caused by the same gene mutation.However,their mechanism is still remained unclear.Objective This study was to observe the phenotype of congenital cataract accompanied with iris dysplasia.Methods Fifteen patients with congenital cataract accompanied with iris dysplasia were included in this study.The slit lamp,gonioscope and ophthalmoscope were used for the examination of the anterior ocular segment,the anterior chamber angle and fundus on all the patients.This study was approved by the Ethic Committee of Second People' s Hospital of Yunnan Province.Written informed consent was obtained from each patient or the custodian prior to any medical procedure.Results All the patients showed binocular involvement.Congenital nuclear cataract with whole coloboma of iris was seen in 7 cases,and 2 cases showed an entire cataract associated with incomplete coloboma of iris.Entire cataract with aniridia was diagnosed in 5 patients,and suture cataract complicated with aniridia was in 1 patient.Conclusions Some regular patterns can be implied between the morphological type of cataract and iris dysplasia,which may be helpful for further study of these diseases.

Research progress in bone marrow mesenchymal stem cell in ophthalmology / 中华实验眼科杂志

Bone marrow mesenchymal stem cell (BMSC) is one kind of the adult stem cells.BMSCs have a strong capacity of self-renewal,the ability to differentiation into different cell types and low immunogenicity.The cells have been successfully differentiated into osteoblast,cartilage cells,adipose cells,cardiac muscle cells and vascular endothelial cells and have a bright future in the field of tissue engineering and cell transplantation.Resent years,BMSCs become the hot spot in ophthalmology due to their advantages.This paper summarizes the effects of BMSCs in the research of ophthalmology.

Repeated morphine pretreatment reduces glutamatergic synaptic potentiation in the nucleus accumbens induced by acute morphine exposure / 生理学报

Repeated exposure to morphine leads to the addiction, which influences its clinical application seriously. The glutamatergic projection from prefrontal cortex (PFC) to the nucleus accumbens (NAc) plays an important role in rewarding effects. It is still unknown whether morphine exposure changes PFC-NAc synaptic transmission. To address this question, in vivo field excitatory postsynaptic potentials (fEPSPs) induced by electric stimulating PFC-NAc projection fibers were recorded to evaluate the effect of acute morphine exposure (10 mg/kg, s.c.) on glutamatergic synaptic transmission in NAc shell of repeated saline/morphine pretreated rats. It was showed that acute morphine exposure enhanced fEPSP amplitude and reduced paired-pulse ratio (PPR) in saline pretreated rats, which could be reversed by following naloxone injection (1 mg/kg, i.p.), an opiate receptor antagonist. However, repeated morphine pretreatment significantly inhibited both the enhancement of fEPSP amplitude and reduction of PPR induced by acute morphine exposure. Those results indicate that the initial morphine exposure enhances PFC-NAc synaptic transmission by pre-synaptic mechanisms, whereas morphine pretreatment occludes this effect.

Ultrastructure observation of rhesus bone marrow mesenchymal stem cell after transplantation of cornea / 中华实验眼科杂志

BackgroundThe quest to look for seed cells is a hot spot of cornea transplant research in solving the problem of the lack of donor. Bone marrow mesenchymal stem cells(BMSCs) have been successfully induced into retinal ganglion cells(RGCs) in vivo,but the successful induction of BMSCs into corneal endothelial cells has not been reported.Objective This experiment was to study the transplantation of BMSCs on corneal endothelial surface using the splitting Descemet's membrane. MethodsFour healthy adult rhesus monkeys were divided into the experimental group ( 3 monkeys) and control group ( 1 monkey). Mesenchymal stem cells (MSCs) were isolated from bone marrow by density gradient centrifugation combined with adhering means. The cultured cells were identified by flow cytometry and its ability to differentiate was determined by allowing them to differentiate into adipocytes in vitro and labeled by 5-bromodeoxyuridine ( BrdU ) for subsequent identification. Corneal grafts of 7 mm in size with tearing of the Descemet' s membrane were prepared in the experimental group and control group. After labeling by 5-bromodeoxyuridine( BrdU ) ,cultured cells were transplanted onto the endothelial surface of cornea grafts in the experimental group, but no cultured cells were seeded in the graft of the control group. The corneal grafts were then sutured in situ, and were removed 1,2 or 3 months after operation to examine the distribution and connection between transplanted cells and their morphologic changes under the electron microscope. Results High purity MSCs were harvested by density gradient centrifugation combined with adhering method. Cultured cells reached confluency after 12 to 16 days, presenting with a spindle shape and parallel or swirling arrangement. Flow cytometry analysis showed that 94.26％ of cells were positive for CD29,7. 51％ for CD34 and 4. 02％ for CD45. Larger nuclei filled with plastosomes, golgiosomes and rough endoplasmic reticula were found on the graft under the transmission electron microscope( TEM ). After 3 weeks, MSCs were differentiated into adipocytes where Oil Red O staining resulted in an orange-red staining in the cytoplasm and blue staining in the nuclei. The transplanted cells attached loosely on the endothelial surface of the corneal graft and came in contact with each other in one month. The shape of the cells appeared as spindle-shaped and polygonal after 2 months and became tightly packed after 3 months. The positive cells retained the BrdU label and presented with brown nuclei. No endothelia cells grew in the cornea graft in the control group, with an absence of BrdU labeling. Conclusions Mesenchymal stem cells can be transplanted onto the corneal endothelial surface successfully and form a monolayer using the centrifugation method, and present with good survival and proliferation ability.

The influence of L-glutamate and carbachol on burst firing of dopaminergic neurons in ventral tegmental area / 生理学报

Burst firing of dopaminergic neurons in ventral tegmental area (VTA) induces a large transient increase in synaptic dopamine (DA) release and thus is considered the reward-related signal. But the mechanisms of burst generation of dopaminergic neuron still remain unclear. This experiment investigated the burst firing of VTA dopaminergic neurons in rat midbrain slices perfused with carbachol and L-glutamate individually or simultaneously to understand the neurotransmitter mechanism underlying burst generation. The results showed that bath application of carbachol (10 μmol/L) and pulse application of L-glutamate (3 mmol/L) both induced burst firing in dopaminergic neuron. Co-application of carbachol and L-glutamate induced burst firing in VTA dopaminergic cells which couldn't be induced to burst by the two chemicals separately. The result indicates that carbachol and L-glutamate co-regulate burst firing of dopaminergic neuron.

The modulation of 4-aminopyridine sensitive potassium channel to bifurcation scenario of the spontaneous neural firing rhythms / 生理学报

Neuronal firing is crucial to the information processing in the nervous system. In order to make a further study of bifurcation scenarios, experiments were performed on neural pacemakers formed at the injured site of rat sciatic nerve subjected to chronic ligatures. We chose the conductance of voltage-dependent potassium ion channels as conditional parameter, and the extracellular calcium concentration as bifurcation parameter, to give a demonstration of how the firing pattern of neural pacemaker responses to dual parameter adjusting. Among 28 preparations observed, 21 were insensitive to dual parameter adjusting since no change of bifurcation scenario structure was detected. On the contrary, the residual 7 preparations showed dramatic bifurcation scenario shifting corresponding to different dual parameter configuration. Briefly, when concentration of 4-aminopyridine (4-AP), a voltage-dependent potassium ion channels blocker, was kept at different level and extracellular Ca2+ concentration was decreased gradually, different bifurcation scenarios of firing patterns were exhibited in an identical neural pacemaker. The two-parameter bifurcation scenarios of experimental neural pacemaker with different parameter configuration were also different. The results show that neural firing pattern is different when the parameter configuration is different, and the bifurcation scenario is a fundamental framework to identify the transitions between firing patterns.