蜜蜂下行神经元的光反应特征

利用电生理细胞外记录方法研究了蜜蜂下行神经元对光的反应特征以及与水平方向上光刺激角度的关系。 光刺激主要引起下行神经元的给光反应和撤光反应,持续性反应很弱。下行神经元的反应依赖于光刺激强度,在一定的强度范围内,随着光强度增大,反应强度也增大根据改变刺激角度引起的反应,在水平方向上最敏感,张角最大,约大于40°。     

猫外膝体神经元兴奋和抑制过程的相互作用

用神经脉冲自动计数的方法,定量地研究了猫外膝体神经元兴奋与抑制过程在时间和空间上的相互作用。1.时间上的相互作用:在亮度变化瞬间,神经细胞的兴奋或抑制过程增强,表现为放电频率暂时地明显增加或减少。这一作用持续的时间(适应时间),瞬变细胞约0.1秒,持续性小感受野细胞约4～8秒,持续性大感受野细胞约40～80秒。2.空间上的相互作用:改变被照射视网膜面积的大小,同时计算神经元的平均放电频率,可以确定外周抑制区的存在、范围和强度。外周抑制可以同时作用于给-撤细胞的给光反应和撤光反应,也可以选择地只抑制其中某一种反应。纯撤光细胞没有外周抑制区。具有大感受野的外膝体神经元,其感受野的大小与背景光的强度有关。在高亮度情况下,感受野变小,有利于改善分辨率;在低亮度下,感受野扩大,有利于提高灵敏度。     

猫外膝体神经元兴奋和抑制过程的相互作用

用神经脉冲自动计数的方法,定量地研究了猫外膝体神经元兴奋与抑制过程在时间和空间上的相互作用。1.时间上的相互作用:在亮度变化瞬间,神经细胞的兴奋或抑制过程增强,表现为放电频率暂时地明显增加或减少。这一作用持续的时间(适应时间),瞬变细胞约0.1秒,持续性小感受野细胞约4～8秒,持续性大感受野细胞约40～80秒。2.空间上的相互作用:改变被照射视网膜面积的大小,同时计算神经元的平均放电频率,可以确定外周抑制区的存在、范围和强度。外周抑制可以同时作用于给-撤细胞的给光反应和撤光反应,也可以选择地只抑制其中某一种反应。纯撤光细胞没有外周抑制区。具有大感受野的外膝体神经元,其感受野的大小与背景光的强度有关。在高亮度情况下,感受野变小,有利于改善分辨率;在低亮度下,感受野扩大,有利于提高灵敏度。     

华虻小叶神经元运动敏感性的研究

用电生理细胞内记录的方法记录了１０个以上小叶神经元对闪光、运动光斑及运动光栅刺激的电生理反应特点,结果表明：（１）小叶神经元对闪光刺激具有特征性反应,细胞对给光和撤光刺激都会表现出不同程度的去极化和超极化,反应的波形不随闪光时间的改变而改变,两次去极化之间的时间间隔与闪光刺激的时间长度成线性关系;（２）小叶神经元对运动光斑的运动速度非常敏感,而对光斑的运动方向的改变却不敏感,尽管有的细胞存在一个能使反应的变化更快的优势方向,但并没有明显的运动方向选择性;（３）小叶神经元对运动光栅的响应频率受光栅的空间频率和运动速度的双重调制,与光栅的运动方向无关。     

具有共同感受野的外膝体神经元的反应相位互补特性

用微电极在猫外膝体进行记录时,有时同一支微电极能同时记录到两个神经元放电,通常是一个给光中心细胞和一个撤光中心细胞。这一对神经元具有共同的感受野,并且对光刺激的反应类型也相同(同属于瞬变型细胞,或者同属于持续型细胞)。当正弦调制的光点投射在它们的感受野中心时,在不同的刺激强度下,给光中心细胞和撤光中心细胞的反应相位彼此相差半个周期(180°)。在低的刺激频率(5Hz)下,给光中心和撤光中心细胞的反应峰值延迟时间(相对于光调制信号的最大和最小值)也相同,表明它们具有相同的反应潜伏期。这种相位互补特性使具有共同感受野的一对细胞工作于“推挽”方式。对于瞬变型细胞来说,尽管它们在单独活动时显示半波整流特性,然而组成互补对以后则能传递全周期光调制信号。     

蜻蜒运动检测神经元的光谱反应

蜻蜒腹神经束上存在着自运动检测神经元和目标运动检测神经元.我们采用了两种视觉刺激条件来测试自运动检测神经元的光谱反应.当采用控制强度和波长的闪光进行测试时、它们的光谱反应曲线与绿色光感受器的光谱灵敏度曲线极其相似,峰值位于500nm处.然而采用运动的条纹进行测试时,它们的峰值却位于560nm处.当用一种颜色的运动图案作为目标放置在另一种颜色背景的前方测试时,发现存在某个目标的照明强度值能使反应下降到自发放电的水平,这表明自运动检测器无法检测这二种颜色的差别,即它们是色盲的、它主要接受来自绿色光感受器的信号.目标运动检测神经元的光谱反应特性与自运动检测神经元的不同,目标运动检测神经元在以380nm至580nm的范围中有着平坦的光谱反应曲线,有时在紫外频段出现峰有(?)前景与背景颜色不同且固定背景光的颜色与强度而改变前景的光强时,神经元的反应不会下降到自发放电水平,当背景为绿色而目标为另一个颜色.特别是兰色时,神经元反应强烈,但当背景为兰色而目标为绿色时,它们的反应相对较弱.这些结果表明目标运动检测神经元是对颜色敏感的.     

蜻蜒运动检测神经元的光谱反应

蜻蜒腹神经束上存在着自运动检测神经元和目标运动检测神经元.我们采用了两种视觉刺激条件来测试自运动检测神经元的光谱反应.当采用控制强度和波长的闪光进行测试时、它们的光谱反应曲线与绿色光感受器的光谱灵敏度曲线极其相似,峰值位于500nm处.然而采用运动的条纹进行测试时,它们的峰值却位于560nm处.当用一种颜色的运动图案作为目标放置在另一种颜色背景的前方测试时,发现存在某个目标的照明强度值能使反应下降到自发放电的水平,这表明自运动检测器无法检测这二种颜色的差别,即它们是色盲的、它主要接受来自绿色光感受器的信号.目标运动检测神经元的光谱反应特性与自运动检测神经元的不同,目标运动检测神经元在以380nm至580nm的范围中有着平坦的光谱反应曲线,有时在紫外频段出现峰有(?)前景与背景颜色不同且固定背景光的颜色与强度而改变前景的光强时,神经元的反应不会下降到自发放电水平,当背景为绿色而目标为另一个颜色.特别是兰色时,神经元反应强烈,但当背景为兰色而目标为绿色时,它们的反应相对较弱.这些结果表明目标运动检测神经元是对颜色敏感的.     

普氏蹄蝠下丘CF-CF联合敏感神经元的声反应

为了研究普氏蹄蝠(Hipposideros pratti)下丘(IC)中恒频-恒频(CF-CF)联合敏感神经元声反应特性,以及易化型和抑制型CF-CF联合敏感神经元在IC高频表征区神经元中所占的比例,实验记录了普氏蹄蝠IC神经元在不同频率和声强下的单声反应以及在不同延迟下的双声反应。本实验采用在体细胞内电生理技术从7只听力正常的蝙蝠上共获得77个IC声敏感神经元。所获得的数据经过处理并应用Sigma Plot 10.0软件作图。研究结果显示,77个神经元中37(48.1%)个为CF-CF联合敏感神经元,且多数为抑制型(24/37),少数为(13/37)易化型。实验结果说明普氏蹄蝠IC中既存在易化型也存在抑制型CF-CF联合敏感神经元,其中抑制型CF-CF联合敏感神经元比易化型所占比例更高。这些CF-CF联合敏感神经元有助于蝙蝠在巡航过程中处理回声信息时进行频谱和时相的整合。     

噪声和二硫化碳对大鼠外膝体神经元光反应的影响及其联合效应

目的：观察噪声或二硫化碳（CS2）暴露对大鼠外侧膝状体（LGB）神经元光反应的影响及二者的联合效应。方法：脉冲噪声刺激和光栅刺激由计算机控制输出,CS2通过皮下注射,运用电生理学方法记录LGB神经元电活动。结果：噪声暴露后有21％的神经元光反应被抑制,当噪声持续时,抑制程度有增强的趋势,呈现出剂量效应关系。不同剂量的CS2暴露,神经元受到不同程度的抑制,亦呈剂量一效应关系。噪声和CS2同时作用时,呈一定的协同作用。结论：噪声或者CS2的单独作用可明显抑制外膝体神经元的光反应,在共同作用时存在联合效应,主要表现为协同效应。     

小鼠听皮层对下丘神经元方位敏感性的调控

应用常规电生理学技术,研究小鼠听皮层对中脑下丘神经元方位敏感性的下行调制.实验记录了198个下丘神经元的听反应,这些神经元的最佳方位角大多数(84.8%)位于听空间对侧20°～50°范围内.根据神经元的方位敏感曲线特征,将这些神经元分为方位选择型,半场型、多峰型和全向型四种调谐模式.电刺激听皮层对绝大多数下丘神经元方位角的范围产生易化(42.0%)或抑制(45.0%)效应,并使59.3%的神经元的最佳方位角发生了转移.结果提示,小鼠下丘神经元具有明显的方位敏感性,听皮层对下丘神经元听觉方位信息处理具有下行调制作用.此研究结果为深入研究中枢听觉信息处理的离皮质调控机制提供了重要实验资料.     

Effects of leg movements on the synaptic activity of descending statocyst interneurons in crayfish,Procambarus clarkii

Crustacean postural control is modulated by behavioral condition. In this study, we investigated how the responses of descending statocyst interneurons were affected during leg movements. Intracellular recording was made from an animal whose statoliths had been replaced with ferrite grains so that statocyst receptors could be activated by magnetic field stimulation. We identified 14 morphological types of statocyst-driven descending interneurons. Statocyst-driven descending interneurons always showed an excitatory response to statocyst stimulation on either ipsilateral or contralateral side to the axon. The response of each statocyst-driven descending interneuron to statocyst stimulation was differently modulated by leg movements in different conditions. During active leg movements, six statocyst-driven descending interneurons were activated regardless of whether a substrate was provided or not. In other two statocyst-driven descending interneurons, the excitatory input during leg movements was stronger when a substrate was provided than when it was not. One statocyst-driven descending interneuron received an excitatory input only during leg movements on a substrate, whereas another statocyst-driven descending interneuron did not receive any input during leg movements both on a substrate and in the air. These results suggest that the descending statocyst pathways are organized in parallel, each cell affected differently by behavioral conditions.Abbreviations EMG electromyogram - NGI nonspiking giant interneuron - SDI statocyst-driven descending interneuron     

Physiological and morphological characterization of olfactory descending interneurons of the male silkworm moth, Bombyx mori

In order to understand the neural mechanisms of pheromone-oriented walking in male silkworm moths, Bombyxmori, we have characterized olfactory responses and three-dimensional structure of two clusters (Group-I, Group-II) of descending interneurons in the brain by intracellular recording and staining with lucifer yellow. Neurons were imaged with laser-scanning confocal microscopy. Group-I and Group-II descending interneurons were classified into three morphological types, respectively. In response to the sex pheromone, bombykol, Type-A Group-I descending interneurons showed characteristic flipflopping activity. The Group-I descending interneurons had dendritic arborizations in the lateral accessory lobe and varicose profiles in the posterior-lateral part of the suboesophageal ganglion where the dendritic arborizations of a neck motor neuron (i.e., cv1 NMN) reside. Other types of Group-I descending interneurons exhibited long-lasting suppression of firing. The pheromonal responses of Group-II descending interneurons fell into two classes: brief excitation and brief inhibition. Type-A Group-II descending interneurons showing brief excitation had blebby processes in the posterior-lateral part of the suboesophageal ganglion. Type-B and Type-C Group-II descending interneurons did not have varicose profiles there. Therefore, the neck motor neuron regulating head turning, which accompanies the pheromone-oriented walking, may be controlled by these two types, flipflop and phasic excitation, of descending activity patterns. Accepted: 2 November 1998     

Quantitative analysis of inputs to somatostatin-immunoreactive descending interneurons in the myenteric plexus of the guinea-pig small intestine

Somatostatin immunoreactivity occurs in a specific subgroup of cholinergic descending interneurons in the myenteric plexus of the guinea-pig small intestine. In the present work, we made light- and electron-microscopic investigations of chemically defined inputs to these neurons, in order that the origins of the connections of other neurons with them could be deduced. Somatostatin-immunoreactive synapses and close contacts were found on the cell bodies and filamentous processes of somatostatin neurons; these were 84% of all inputs. It is thus confirmed that this class of interneuron forms chains that project anally. Descending interneurons with immunoreactivity for nitric oxide synthase provided 14% of inputs to somatostatin-immunoreactive descending interneurons. An antiserum against a calcium-binding protein, calbindin, was used as marker for the majority of intrinsic primary afferent neurons, AH/Dogiel type II neurons; this class of neurons provided only 2.5% of the inputs to somatostatin-immunoreactive descending interneurons. We conclude that somatostatin-immunoreactive descending interneurons are involved in the conduction of impulses distally along the full length of the small intestine, but receive only a minor input from calbindin-immunoreactive primary afferent neurons.     

Responses of descending interneurons to stimulation of wind head receptors in locust

Responses of descending interneurons of the thoracic nerve chain ofLocusta migratoria L. to wind stimulation of the head receptors concerned with the activation of the insect's flight were investigated by means of extracellular microelectrode recordings from their axons. Altogether 11 types of descending effects transmitted by these interneurons to neurons of the segmental ganglia were detected. Ipsilateral and contralateral wind stimulation of the receptors can not only activate hitherto silent interneurons but also effectively modify the character of discharges from spontaneously active, discharging neurons. This influence may be either excitatory (increased spontaneous firing rate) or inhibitory (decreased rate or total abolition of spontaneous discharges). Some descending interneurons give rise not only to on-responses but also to typical off-responses to stimulation. The possible functional role of some of the observed effects in the mechanisms triggering and maintaining the insect's flight is discussed.I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Biological Research Institute, Hungarian Academy of Sciences, Tihany. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 602–610, November–December, 1973.     

Reticulofugal influences of interneurons in the lateral region of gray matter of the cat spinal cord

Responses of lumbar interneurons located in the most lateral regions of Rexed's laminae IV–VII to stimulation of the medial longitudinal bundle and gigantocellular reticular nucleus of medullary pyramids, red nucleus, and peripheral nerves were investigated in cats anesthetized with pentobarbital. Stimulation of the reticulospinal fibers evoked monosynaptic excitation of many interneurons specialized for transmitting activity of the lateral descending systems, but not of peripheral afferents. Convergence of excitatory influences of all three descending systems (cortico-, rubro-, and reticulospinal) was observed on some cells of this group. In addition, monosynaptic "reticular" E PSPs appeared in interneurons transmitting activity of group Ia muscle fibers and in some interneurons of the flexor reflex afferent system. Stimulation of reticulospinal fibers evoked IPSPs in some neurons of this last group. Neurons not exposed to reticulofugal influences (both specialized neurons and interneurons of segmental reflex arcs) were located chiefly in the dorsal zones of the region studied. Recordings were also obtained from single fibers of the lateral reticulospinal tracts (conduction velocity from 26 to 81 m/sec).A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 525–536, September–October, 1973.     

Sources of inputs to longitudinal muscle motor neurons and ascending interneurons in the guinea-pig small intestine

Light- and electron-microscopic studies were used to investigate connections between specific subgroups of neurons in the myenteric plexus of the guineapig small intestine. Inputs to two classes of calretinin-immunoreactive (IR) nerve cells, longitudinal muscle motor neurons and ascending interneurons, were examined. Inputs from calbindin-IR primary sensory neurons and from three classes of descending interneurons were studied. Electron-microscopic analysis showed that calbindin-IR axons formed two types of inputs, synapses and close contacts, on calretinin-IR neurons. About 40% of inputs to the longitudinal muscle motor neurons and 70% to ascending interneurons were calbindin-IR. Approximately 50% of longitudinal muscle motor neurons were surrounded by bombesin-IR dense pericellular baskets and 40% by closely apposed varicosities. At the electron-microscope level, the bombesin-IR varicosities were found to form synapses and close contacts with the motor neurons. Dense pericellular baskets with bombesin-IR surrounded 36% of all ascending interneurons, and a further 17% had closely apposed varicosities. Somatostatin-and 5-HT-IR descending interneurons provided no dense pericellular baskets to calretinin-IR nerve cells. Thus, calretinin-IR, longitudinal muscle motor neurons and ascending interneurons receive direct synaptic inputs from intrinsic primary sensory neurons and from non-cholinergic, bombesin-IR, descending interneurons.     

Synaptic transmission in simple motility reflex pathways excited by distension in guinea pig distal colon

We examined specific receptor/transmitter combinations used at functionally identified synapses in ascending and descending reflex pathways of guinea pig distal colon. Excitatory (EJPs) or inhibitory junction potentials (IJPs) were recorded intracellularly from nicardipine-paralyzed circular smooth muscle in either the oral or anal recording chamber of a three-chambered organ bath, respectively. Blockade of synaptic transmission in the central chamber with a 0.25 mM Ca2+/12 mM Mg2+ solution abolished EJPs evoked by distension applied either in the central or the far (anal) chamber. IJPs evoked by distension in the central or the far (oral) chamber were depressed to approximately 50% of control. Hexamethonium (nicotinic receptor antagonist, 200 microM) in the central chamber reduced IJPs evoked by far or central distension to 50%, whereas EJPs evoked by far distension were abolished and EJPs evoked by central distension were reduced to 70% of control. Hexamethonium in the recording chambers reduced both IJPs and EJPs evoked by central distension to approximately 50%. EJPs in the ascending pathway were unaffected by blockade of muscarinic receptors in the central chamber or blockade of neurokinin 3 tachykinin receptors in this or the recording chamber. In the descending pathway, blockade of P2 receptors in the same chambers had only a minor effect on distension-evoked IJPs. Thus some intrinsic sensory neurons of guinea pig colon have long descending projections (>30 mm), but ascending projections of <15 mm. In contrast to the ileum, transmission between ascending or descending interneurons and from sensory neurons to descending interneurons is predominantly via nicotinic receptors; but transmission to inhibitory or excitatory motoneurons and from sensory neurons to ascending interneurons involves nicotinic and other unidentified receptors.     

Transmission of descending activity evoked by prolonged stimulation of the pyramids and red nucleus by groups of spinal interneurons

Responses of two groups of spinal interneurons to prolonged stimulation of the medullary pyramids and the red nucleus by repetitive and random sequences of stimuli were investigated in cats anesthetized with pentobarbital. Interneurons specialized for transmission of descending, but not peripheral, effects were excited by impulses from both higher structures; the evoked activity was stable and stationary in character in response to stimulation within the range from 20–30 to 75–100/sec. The response of interneurons activated by flexor reflex afferents was more complex and, as a rule, it was not stationary. Prolonged pyramidal stimulation led to an increase in the mean spontaneous firing rate, while stimulation of the red nucleus inhibited spontaneous activity. Statistical analysis of the records of unit activity on the "Dnepr'-1" computer was used to study some possible mechanisms of the transformation of activity in the lateral descending systems by these groups of interneurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 644–653, November–December, 1973.     

Constancies in the neuronal architecture of the suboesophageal ganglion at metamorphosis in the beetleTenebrio molitor L.

Summary Topological organization of identified neurons has been characterized for the larval, pupal and imaginal suboeosphageal neuropil of the meal-worm beetleTenebrio molitor. Neuronal fate mapping allows identification of individually persisting neurons in the metamorphosing suboesophageal ganglion ofTenebrio. Analysis was performed on interneurons characterized by serotonin and CCAP (crustacean cardioactive peptide) immunohistochemistry, on motoneurons that innervate the dorsal and ventral longitudinal muscles, and on suboesophageal descending neurons. All these different populations of neurons show topologically invariant features throughout metamorphosis. Motoneurons, interneurons, and descending suboesophageal neurons of the imaginal suboeosphageal ganglion embody individually persisting larval interneurons. Impacts for a functional interpretation of the neuronal architecture of the suboesophageal ganglion are discussed.