Of Stg Neuron Spontaneous Discharge Transition To The Preliminary Study Of The Law

Understanding the genesis of rhythmic motor patterns such as walking and swimming has long been a fundamental goal of neuroscience. Invertebrate preparations have always played a prominent role in these studies because these preparations are often easily maintained in vitro and often have anatomically distributed nervous systems (as opposed to the highly centralized systems found in vertebrates), large neurons that are easily recorded from and repeatedly identifiable in different animals of the same species, and fixed neuron populations and synaptic connections. Indeed, the crayfish and locust were the first preparations in which it was unambiguously demonstrated that central pattern generators (CPG)-neural networks capable of spontaneously producing rhythmic, patterned neural outputs in the absence of sensory feedback or patterned central input-exist. Subsequent work in a large variety of systems showed that in all cases, CPG generate the fundamental rhythmicity and phasing of rhythmic motor patterns.The stomatogastric nervous system(STNS) are present even in the absence of sensory feedback and are typical CPGs. The STNS controls rhythmic movements in different parts of the stomach in decapod crustaceans. The stomatogastric ganglion(STG) contains two networks, one controlling the teeth of the gastric mill (the gastric CPG) and one controlling the pyloric filter apparatus (the pyloric CPG). These networks are composed of neurons that act both as part of their respective CPG and as motor neurons that send axons to specific stomach muscles. Many of these neurons also express rhythmic activity of multiple patterns at the same time, reflecting influences of inter-network and other networks. These interactions are mediated by direct chemical and electrical synapses cell-to-cell.For any CPG, the mechanisms generating the rhythm (rhythmogenesis), and those involved with the formation of the sequential pattern are the most important to understand. The genesis of the rhythm is generally framed as being due to two possible mechanisms:individual cellular electrical characteristic and various types of synaptic interactions that must be tuned to work together. Nevertheless, cellular and synaptic mechanisms for the generation of rhythmic activity and the formation of a multi-phasic burst pattern are still not sufficiently understood in this system.The purpose of this work is to describe complex and diverse firing pattern and pattern transition exhibited in neuron, the characteristics of the electrical activity of functionally isolated single neurons in the stomatogastric ganglion (STG)of crayfish during the alteration of the extracellular calcium concentration and blockade of calcium-dependent potassium channel were observed by using intracellular recording method. EGTA(a chelating agent of calcium) was used to change the extracellular calcium concentration ([Ca2+]。) while tetraethylammonium (TEA) was used to block the calcium-dependent potassium channel after a single neuron in the STG was functionally isolated by perfusing the neurons with atropine and picrotoxin, which blocked the inhibitory acetylcholine synapses and glutamatergic synapses respectively.The main results are as follows:1.Rhythmic patterns of STG neurons spontaneous firingWhen the STG was perfused continuously with normal perfusate, abundant spontaneous firing rhythm patterns were observed, such as the two rhythmic period 1 spiking with low voltage, continuity, high-frequency and high voltage, continuity, high-frequency; the spiking pattern with irregular firing duration, occurrences and duration of quiescence; the low-frequency bursting with long firing trains, long plateau duration, big potential between plateau and resting potential; and the high-frequency bursting with short firing trains, short plateau duration, small potential between plateau and resting potential.2. Pyloric rhythm is affected by neuronal property and network interactionThe bursting phase of the different pyloric neurons formed the three-phase rhythm according to some relatively fixed order, which in turn controls the separation, digestion and absorption of food in the muscle movement. The dynamics of pyloric networks depends on the ongoing interplay between the intrinsic properties of the neurons that make up networks and the strength, time course, and time-dependent properties of the synapses among them.3.The dynamic ionic mechanism of the initiation and termination of burst in STG neuronsIn the bursting pacemaker potential oscillation, calcium influx increases the level of intracellular calcium, thereby activates calcium-dependent potassium current, and results in potassium outflow and membrane potential repolarization. The burst disappear, to the quiescence; in the quiescence, calcium influx is terminated and calcium-dependent potassium current is decreased, the membrane potential uplift to a threshold level, oscillatory bursting appeared again. Thereby STG neurons alternated between the oscillation and resting state, and produced bursting.4.Regular transitions in spontaneous firing patterns of isolated STG neuronsWhen [Ca2+]。was decreased, the membrane potential of neuron was increased, and the electronic activity was changed from polarized resting state to bursting firstly, and then to spiking, at last to the depolarized resting state. When TEA concentration([TEA]。)was increased, the membrane potential also increased, the electronic activity was changed from polarized resting state to bursting firstly, and then to spiking, and the duration of the burst was increased. When [Ca2+]。was increased or [TEA]。was decreased, the reversed changing procedure of the electrical activity was observed. The results indicated that the electronic activity pattern of STG neurons exhibit regular transition with respect to the changes of the physiological parameters, and the changes of both [Ca2+]。and conductance of the calcium-dependent potassium channel influence the generation of firing rhythm and pattern transitions. The transition regularity could explain the reason of complex and diverse rhythm patterns generated in STG neuron.