Artificial Polarization Research Articles

Modulation of electrical activity of neuron RPal ofHelix pomatia

Neuron RPa2 ofHelix pomatia can generate rhythmic (beating) or periodic (bursting) activity. A spontaneous switch from beating to bursting activity takes place in the course of tens of minutes. Similar changes in electrical activity can be induced by the addition of the water-soluble fraction obtained from a homogenate of snail ganglia to the experimental chamber. Artificial polarization of the membrane of neuron RPa2 by asteady inward current leads to an increase in the duration of intervals between bursts and to a decrease in the number of action potentials in the burst. With an increase in amplitude of the polarizing current, action potential generation ceases completely, but generation of waves of membrane potential persists. If the voltage on the neuron membrane is clamped, periodic fluctuations of membrane current disappear. It is suggested that action potential generation by neurons RPa2 is determined by the properties of the potential-dependent conductance of its membrane, i.e., that it is endogenous in origin and can be regulated by compounds acting on the membrane. These compounds, secreted by other neurons, resemble neurotransmitters or neurohormones.

Artificial polarization anomalies from holographic gratings

Abstract An aluminum reflection grating made holographically was found to display polarization anomalies when illuminated with p-polarized light. Additional anomalies were detected for both p- and s-polarizations after the grating was coated with a layer of dielectric (410 nm of photoresist). These new anomalies have been interpreted in terms of the optical guided modes of a thin film dielectric waveguide bounded on one side by metal and on the other by vacuum.

Effects of trans-membrane polarization and TEA injection on monosynaptic actions from motor cortex, red nucleus and group Ia afferents on lumbar motoneurons in the monkey.

Abstract The monosynaptic EPSPs evoked from supraspinal structures and muscle afferents in alpha-motoneurons were investigated in the rhesus monkeys with the aid of intracellular recording. There was a statistically significant difference in the time course of cortico-motoneuronal, rubro-motoneuronal and group Ia monosynaptic EPSPs but a relatively small difference between these inputs in the sensitivity to the artificial polarization. No correlation was found between the sensitivity of monosynaptic actions to injected currents and the rise time of EPSP. Tetraethylammonium (TEA) injection into the neuroplasm induced a large increase in the ability of the applied currents to affect the magnitude of the monosynaptic EPSPs, and shifted the extrapolated equilibrium potential in the negative direction. TEA accentuated the trend of cortico-motoneuronal EPSPs toward a more negative equilibrium potential as compared with the group Ia and rubro-motoneuronal EPSPs recorded in the same cell. The early phase of all monosynaptic EPSPs could not be reversed by depolarizing currents in normal and TEA-treated motoneurons and when superimposed on the plateau of depolarization of TEA-prolonged action potential. The results are discussed in relation to the ionic mechanisms of excitatory subsynaptic membrane and to the location of the synaptic sites.

Effect of polarizing currents on potentials evoked in neurons of the ventral leaf of nucleus reticularis thalami by intralaminar stimulation

Intracellular recordings from neurons in the ventral leaf of nucleus reticularis thalami revealed two modes of responsiveness to repetitive intralaminar stimulation in encephàle isolé cats. One group of cells showed no hyperpolarizing potentials, responding only with depolarizations of up to 18 mv and 90 msec which were enhanced 15–80% by the intracellular injection of hyperpolarizing currents. A second group responded with a few or no spikes to the initial stimulus, while later shocks triggered depolarizations with maximum amplitudes of 8–15 mv and durations between 40 and 60 msec which were followed by hyperpolarizations of longer duration and equal or greater amplitude. Artificial membrane polarization exerted a very limited or no effect on the depolarizations in these neurons, while the hyperpolarizations were reduced up to 30% in some units but remained unchanged in others. It is concluded that the depolarizations in both cell populations were EPSP which may have been generated at different synaptic locations and that the hyperpolarizations were IPSP which may have been enhanced by an additional disfacilatatory process.

White-noise analysis of a neuron chain: an application of the Wiener theory.

The Wiener theory of nonlinear system identification was applied to a three-stage neuron chain in the catfish retina in order to determine the functional relationship between the artificial polarization of the horizontal cell membrane potential and the resulting discharge of the ganglion cell. A mathematical model was obtained that can predict quantitatively, with reasonable accuracy, the nonlinear, dynamic behavior of the neuron chain. The applicability of the method is discussed. We conclude that this is a very powerful method in the analysis of information transfer in the central nervous system.

Horizontal cells of the retina as regulators of synaptic transmission

1. During hyperpolarization of a horizontal cell of the turtle retina to 100–150 mV through an intracellular microelectrode, the hyperpolarizing response of this cell to light (the S-potential) increases, while during depolarization it decreases. This effect, difficult to explain from the standpoint of the membrane theory, may be attributed to the presynaptic effect of the current on the photoreceptor-horizontal cell synapse. 2. Artificial polarization of one horizontal cell through an intracellular microelectrode may cause changes in the local ERG, representing the response of bipolar cells situated close to this cell. Depolarization causes a decrease in the ERG; hyperpolarization an increase. If short hyperpolarizing pulses of current (condenser discharges) are passed through a horizontal cell, potentials similar to the d wave of the ERG arrive in the layer of bipolar cells. The electrical response of bipolar cells to the current differs under different conditions of illumination. 3. The results obtained suggest that the horizontal cells are regulators of synaptic transmission between the photoreceptors and bipolar cells. The available evidence (electrophysiological and morphological) indicates that this regulation is effected through an electric current generated by the postsynaptic membrane of the horizontal cells.

Artificial Rotatory Polarization

Artificial Rotatory Polarization