Information processing in the femur-tibia control loop of stick insects

The complicated response characteristics of the identified nonspiking interneuron type E4 upon elongation stimuli to the femoral chordotonal organ (fCO) can be obtained by a computer simulation using the neuronal network simulator BioSim, if the following assumptions were introduced: (1) The interneurons receive direct excitatory input from position- and velocity-sensitive fCO afferents but also, in parallel delayed inhibition from the same velocity-sensitive afferents. (2) Position-sensitive afferents in part show adaptation with a rather long time-constant. A subsequent experimental analysis demonstrated that all these assumptions fit the reality: (1) Interneurons of type E4 receive direct excitatory input from fCO afferents. (2) Interneurons of type E4 are affected by velocity dependent delayed inhibitory inputs from the fCO. (3) The fCO does contain adapting position-sensitive sensory neurons, which have not been described before. The described principle of the information processing is also able to generate the response in interneurons of type E6 with less steep amplitude-velocity characteristic due to a different weighting of the direct excitation and delayed inhibition.Abbreviations EPSP excitatory postsynaptic potential - FETi fast extensor tibiae motor neuron - fCO femoral chordotonal organ - FT-control loop femur-tibia control loop - IPSP inhibitory postsynaptic potential - SETi slow extensor tibiae motor neuron     

Further studies of the effects of somatostatin and related peptides in area CA1 of rabbit hippocampus

1. In slice studies of mature and immature CA1 hippocampal pyramidal cells from rabbit, somatostatin 14 (SS14), the related peptide somatostatin 28(1-12) [SS(1-12)], and the synthetic analogue of somatostatin 14, SMS-201995 (SMS), had similar effects. When pressure-ejected onto cell somata, these peptides elicited depolarizations, often accompanied by action potential discharge. When applied to dendrites, the peptides produced depolarizations or hyperpolarizations. 2. When a large amount of one of the three somatostatin-related (SS) peptides was applied to the slice at some distance from the impaled cell, hyperpolarizations were observed that were not always blocked by tetrodotoxin (TTX) or low Ca2+. Since SS peptides were also found to depolarize interneurons in area CA1, it seems likely that the hyperpolarizations that were blocked by TTX or low Ca2+ were mediated via excitation of interneurons that in turn hyperpolarized pyramidal cells. 3. All SS peptides also had long-lasting effects on CA1 pyramidal cells that led to spontaneous firing of action potentials and an increase in the number of action potentials discharged in response to a given depolarizing current pulse; the spontaneous discharge effect was blocked by TTX or low Ca2+ plus Mn2+ and, thus, appeared to have a presynaptic mechanism. However, the increase in discharge in response to a constant depolarizing current pulse was not dependent on intact synaptic transmission and, therefore, was attributable to a direct postsynaptic effect of the SS peptides.     

γ节律振荡机制在视觉研究中的新进展

γ节律振荡是大脑皮质中常见的,频率在30～80 Hz之间的神经振荡模式,在初级视觉通道中能观察到多种起源的γ节律振荡.在小鼠、猫与猴V1的视觉诱发的γ节律振荡主要起源于L2/3和L4B,并对刺激参数敏感.猫与小鼠初级视觉通道(视网膜、LGN与V1)中观察到起源于视网膜由亮度诱发的高频γ节律振荡;在猴LGN却没有观察到γ节律振荡,而在V1上记录到亮度诱发的γ活动.γ节律振荡的产生与抑制性中间神经元网络有重要的关系,其中抑制性中间神经元中PV细胞被认为与自发γ节律振荡的产生相关. SOM细胞的参与对低频γ节律振荡(20～40 Hz)的产生起到关键作用;而光栅诱发的高频γ节律振荡(65～80 Hz)主要与PV细胞有关.动物在不同生理状态、发育阶段与脑疾病状态下光栅诱发的γ节律振荡存在较大差异,反映大脑对视觉信息加工的变化.     

Neural progenitor diversity and their therapeutic potential for spinal cord repair

Development of the central nervous system (CNS) requires progressive differentiation of neural stem cells, which generate a variety of neural progenitors with distinct properties and differentiation potentials in a spatiotemporally restricted manner. The underlying mechanisms of neural progenitor diversification during development started to be unraveled over the past years. We have addressed these questions by v-myc immortalization method and generation of neural progenitor clones. These clones are served as in vitro models of neural differentiation and cellular tools for transplantation in animal models of neurological disorders including spinal cord injury. In this review, we will discuss features of two neural progenitor types (radial glia and GABAergic interneuron progenitor) and diversification even within each progenitor type. We will also discuss pathophysiology of spinal cord injury and our ongoing research to address both motor and sensory malfunctions by transplantation of these neural progenitors.     

A unique expression pattern of Tbx10 in the hindbrain as revealed by Tbx10LacZ allele

To study the expression/function of Tbx10, a T‐box gene, Tbx10LacZ/+ mice were established by replacing the T‐box coding region with a LacZ gene. X‐gal staining showed that LacZ+ cells were localized to two‐cell populations in rhombomere 4 and rhombomere 6. No significant differences in the locations of LacZ+ cells were found between Tbx10LacZ/+ and Tbx10LacZ/LacZ mice, and the Tbx10LacZ/LacZ mice were viable and fertile. We found that the LacZ+ cells are present in both embryonic and adult mice. Histological studies suggest that the rhombomere 4‐derived LacZ+ cells are a subpopulation of the ventral interneurons in the pons.     

Serotonin, social status and aggression

Serotonin, social status and aggression appear to be linked in many animal species, including humans. The linkages are complex,and, for the most part, details relating the amine to the behavior remain obscure. During the past year, important advances have been made in a crustacean model system relating serotonin and aggression. The findings include the demonstration that serotonin injections will cause transient reversals in the unwillingness of subordinate animals to engage in agonistic encounters, and that at specific synaptic sites involved in activation of escape behavior, the direction of the modulation by serotonin depends on the social status of the animal.     

Physiological characteristics of the synaptic response of an identified sensory nonspiking interneuron in the crayfish Procambarus clarkii girard

Voltage-dependent variability in the shape of synaptic responses of the LDS interneuron, an identified nonspiking cell of crayfish, to mechanosensory stimulation was studied using intracellular recording and current injection techniques. Stimulation of the sensory root ipsilateral to the interneuron soma evoked a large depolarizing synaptic response. Its peak amplitude was decreased and the time course was shortened when the LDS interneuron was depolarized by current injection. When the cell was hyperpolarized, the peak amplitude was increased and the time course was prolonged. Upon large hyperpolarization, however, the amplitude did not increase further while the time course showed a slight decrease. The dendritic membrane of the LDS interneuron was found to show an outward rectification upon depolarization and an inward rectification upon large hyperpolarization. Current injection experiments at varying membrane potentials revealed that the voltage-dependent changes in the shape of the synaptic response were based on an increase in membrane conductance due to the rectifying properties of the LDS interneuron. Stimulation of the contralateral root evoked a small depolarizing potential comprising an early excitatory response and a later inhibitory component. Its shape also varied depending on the membrane potential in a manner similar to that of the synaptic response evoked ipsilaterally.     

An identified cerebral interneuron initiates different elements of prey capture behavior in the pteropod mollusc,Clione limacina

The prey capture phase of feeding behavior in the pteropod molluscClione limacina consists of an explosive extrusion of buccal cones, specialized oral appendages which are used to catch the prey, and significant acceleration of swimming. Several groups of neurons which control different components of prey capture behavior inClione have been previously identified in the CNS. However, the question of their coordination in order to develop a normal behavioral reaction still remains open. We describe here a cerebral interneuron which has wide-spread excitatory and inhibitory effects on a number of neurons in the cerebral and pedal ganglia, directed toward the initiation of prey capture behavior inClione. This bilaterally symmetrical neuron, designated Cr-PC (Cerebral interneuron initiating Prey Capture), produced monosynaptic activation of Cr-A motoneurons, which control buccal cone extrusion, and inhibition of Cr-B and Cr-L motoneurons, whose spike activities maintain buccal cones in a withdrawn position inside the head in non-feeding animals. In addition, Cr-PC produced monosynaptic activation of a number of swim motoneurons and interneurons of the swim central pattern generator (CPG) in the pedal ganglia, pedal serotonergic Pd-SW neurons involved in a peripheral modulation of swimming and the serotonergic Heart Excitor neuron.     

螽斯听觉中间神经元TN2的声反应特征以及GABA对其影响

采用单细胞电生理记录技术,对螽斯Ｇａｍｐｏｃｌｅｉｓ ｇｒａｔｉｏｓａ听觉双轴突中间神经元ＴＮ２的声反应放电活动的基本特征进行了观测,发现ＴＮ２的放电模式为“ｐｈａｓｉｃ”型,最敏感频率为１３ｋＨｚ,反应阈值为３１ｄＢ ＳＰＬ,是一个高灵敏、宽带通的神经元。还研究了抑制性神经递质ＧＡＢＡ及其拮抗剂苦毒素对ＴＮ２声反应的影响,发现ＧＡＢＡ能抑制ＴＮ２的放电活动,而苦毒素则将其放电模式改变为“ｔｏｎｉ     

Patch-clamp recordings of spiking and nonspiking interneurons from rabbit olfactory bulb slices: Membrane properties and ionic currents

Summary Physiological and morphological properties of rabbit, Oryctolagus cuniculus, olfactory bulb interneurons were characterized by using a thin slice preparation in combination with patch-clamp measurements and Lucifer Yellow fills. Two types of interneurons, periglomerular (PG) and juxtaglomerular (JG) cells, were unequivocally distinguished in the glomerular layer. Their properties were compared to those of mitral cells. PG cells closely resembled previously described periglomerular cells in their morphology. During current clamp recording these neurons were characterized by their lack of action potentials upon depolarization. Consistent with these results no Na⁺ currents could be elicited in voltage clamp experiments. Two types of outward K⁺ currents were distinguished: one which inactivated and one which did not. From their morphology JG cells appear to be either short axon cells or external tufted cells. JG cells always responded with a single, TTX-blockable action potential in response to maintained current injection. Two types of membrane currents were identified in JG cells during voltage clamp: a fast, inactivating Na⁺ current that was fully activated at — 80 mV, and a sustained outward current that shared some properties with a delayed rectifier K⁺ current. The particular relationship between the voltage dependence of the Na⁺ and K⁺ currents appeared to preclude repetitive spike activity.Abbreviations JG juxtraglomerular interneuron - LOT lateral olfactory tract - M/T mitral/tufted (cells) - PG periglomerular - SA short axon