Recording Of Synaptic Potentials Research Articles

Electrophysiological analysis of synaptic transmission in Drosophila.

Synaptic transmission is dynamic, plastic, and highly regulated. Drosophila is an advantageous model system for genetic and molecular studies of presynaptic and postsynaptic mechanisms and plasticity. Electrical recordings of synaptic responses represent a wide-spread approach to study neuronal signaling and synaptic transmission. We discuss experimental techniques that allow monitoring synaptic transmission in Drosophila neuromuscular and central systems. Recordings of synaptic potentials or currents at the larval neuromuscular junction (NMJ) are most common and provide numerous technical advantages due to robustness of the preparation, large and identifiable muscles, and synaptic boutons which can be readily visualized. In particular, focal macropatch recordings combined with the analysis of neurosecretory quanta enable rigorous quantification of the magnitude and kinetics of transmitter release. Patch-clamp recordings of synaptic transmission from the embryonic NMJ enable overcoming the problem of lethality in mutant lines. Recordings from the adult NMJ proved instrumental in the studies of temperature-sensitive paralytic mutants. Genetic studies of behavioral learning in Drosophila compel an investigation of synaptic transmission in the central nervous system (CNS), including primary cultured neurons and an intact brain. Cholinergic and GABAergic synaptic transmission has been recorded from the Drosophila CNS both in vitro and in vivo. In vivo patch-clamp recordings of synaptic transmission from the neurons in the olfactory pathway is a very powerful approach, which has a potential to elucidate how synaptic transmission is associated with behavioral learning. WIREs Dev Biol 2017, 6:e277. doi: 10.1002/wdev.277 For further resources related to this article, please visit the WIREs website.

Characteristics of background and evoked discharges of multireceptive neurons in lumbar spinal cord of cat

1. Intracellular recordings were made in laminae III-V of the dorsal horn of the cat spinal cord from a group of multireceptive neurons that exhibited similar physiological properties. The background discharge contained irregular and occasional clusters of action potentials, each arising from a complex excitatory postsynaptic potential (EPSP); brushing elicited more frequent clusters containing more action potentials, whereas noxious heating elicited more regular firing, with action potentials arising singly. The distribution of interspike intervals (ISIs) was measured for the background and heat-evoked discharges and revealed characteristic differences in pattern between the two states. 2. Statistical tests were applied to the point process of times of occurrence of spikes within a discharge to establish stationary, to identify renewal instants, and to describe the process between renewal instants. In each case, the statistical description of the discharge was related to the physiological state of the neuron as revealed by recording of synaptic potentials and analysis of the different activating inputs. 3. Background discharge was stationary, and spikes occurred singly or occasionally in clusters. The data were therefore analyzed as a series of "bursts," where a burst could be made up of one or more spikes. Examination of the pattern of serial dependence led to the conclusion that the point process renewed itself after each burst. This, together with the distribution of the intervals between bursts, suggested that bursts were triggered by single, distinct events, which occurred randomly at a slightly and randomly varying average rate. The variation in the number of spikes in a burst suggested random variation in the strength of the physiological trigger. 4. Clusters of action potentials arising from a complex EPSP could be produced by simultaneous stimulation of a number of fast-conducting A beta fibers in the periphery and gentle mechanical stimulation, whereas stimulation of slow C fibers and noxious heat evoked discrete EPSPs from which action potentials arose singly. It was, therefore, concluded that background activity was, at least in part, the result of random activity in a randomly varying number of A beta primary afferent fibers, which could arise from operative procedures. 5. The discharge evoked by heat was stationary, and the absence of serial dependence established that the point process renewed itself after every spike and was, therefore, a simple renewal process. The distribution of the ISIs suggested that each spike was triggered by a randomly occurring physiological event.(ABSTRACT TRUNCATED AT 400 WORDS)

Location and functioning of transmitter release sites in frog neuromuscular junction

End-plate potentials (EPP) and miniature EPP (MEPP) were recorded in a single neuromuscular synapse of the frog sartorius muscle by means of two microelectrodes with a resistance of 0.5–2.0 Mθ. Groups of signals (fields), reflecting transmitter secretion in spatially distinct release sites were identified by extracellular recording on MEPP amplitude scatter diagrams. Release sites in the nerve ending were found to be unevenly distributed, to be grouped in certain areas, and to differ in their probability of secretion of a quantum of transmitter. Comparison of fields on MEPP and uniquantal EPP amplitude scatter diagrams in solution with low Ca++ concentration (0.2–0.4 mM) showed that ability to induce evoked and spontaneous transmitter release at the release site differs, and that sometimes a release site does not participate in evoked secretion. The results of simultaneous recording of synaptic potentials using extra- and intracellular electrodes indicate that transmitter secretion in spatially distinct groups of release sites leads to the appearance of polymodality in the distribution of amplitudes of intracellularly recorded MEPP and uniquantal EPP.

Mechanical properties of a slow muscle in the cockroach.

The mechanical properties of the metacoxal muscle, 177d, in the cockroach, Periplaneta americana, was investigated. The muscle exhibited a mean resting tension of 2.6 +/- 1.3g SD. Neurally evoked tension summed with the resting tension and the relaxation phase of the evoked tension varied from less than 1 s to several minutes. This residual tension varied not only in duration but also in amplitude. Stimulation of inhibitory axons increased the rate of relaxation and thereby abolished the residual tension. However, inhibitory stimulation never reduced the resting tension. Stimulation of the main leg nerve at several times the threshold of the inhibitory axons could evoke residual tension. Recording of synaptic potentials from the two histochemically different fiber types (dorsal and ventral groups) revealed large hyperpolarizations in the ventral fibers and decreased duration and amplitude of excitatory potentials in the dorsal fibers. These results suggest that there are a variety of ways in which tension can be evoked, maintained, and controlled in these muscles.