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D Oertel

Publications and source records attributed to D Oertel.

44 records · Page 3Linked to original sources
PubMed1983

Synaptic responses and electrical properties of cells in brain slices of the mouse anteroventral cochlear nucleus.

Intracellular recordings were made from cells in brain slices of the anteroventral cochlear nucleus. Responses to electrical stimulation of the stump of the auditory nerve were: (1) all-or-none, following the stimulus with no delay, and insensitive to the removal of extracellular Ca2+, probably representing the firing of directly stimulated auditory nerve fibers, or (2) graded, excitatory postsynaptic potentials, with synaptic delays of about 0.7 msec, which were often followed by graded, inhibitory synaptic potentials with synaptic delays of 1.2 msec or longer. The excitatory and inhibitory synaptic potentials were abolished by the removal of extracellular Ca2+. The result that delays of inhibitory synaptic responses were at least 2 times as long as those of excitatory ones indicates that probably an additional synapse was interposed. Responses to intracellularly injected current pulses show that cells in the anteroventral cochlear nucleus have one of two types of electrical characteristics. Type I properties are characterized by linear current-voltage relationships in the subthreshold voltage range and large, regularly firing action potentials in the suprathreshold range. Type II properties are characterized by nonlinear current-voltage relationships; suprathreshold depolarization elicits only one or two small action potentials. Type II characteristics are particularly well suited for maintaining the information contained in the timing and patterns of firing of the auditory nerve fibers.

Action Potentials↗
PubMed1981

Transformation of signals by interneurones in the barnacle's visual pathway.

1. The photoreceptors of the median eye of the giant barnacle drive decrementally-conducting neurones in the supraoesophageal ganglion termed ;inverting cells' (I-cells) which in turn drive impulse-producing neurones termed ;amplifying cells' (A-cells). Using intracellular recording techniques we have studied the role of I-cells in visual processing.2. Horseradish peroxidase injections show that I-cells are interneurones whose processes are confined to the regions of the photoreceptor terminals on both sides of the bilaterally symmetrical ganglion.3. In the dark, I-cell membrane potentials (-45 mV) are considerably less negative than those of other ganglion cells (-60 to -70 mV). At the onset of a maintained light, I-cells undergo a transient peak hyperpolarization which declines to a steady-state response. Both response components are graded with light intensity.4. The reversal potential of the peak of the I-cell light response depends on the external K(+) concentration more strongly than does the dark resting potential (3-30 mm-K(+)). This evidence indicates that the hyperpolarization results from an increase in the cell's permeability to K(+) ions.5. At the offset of light an I-cell undergoes a transient depolarization that overshoots the dark membrane potential. Dimming of a background light can also cause the I-cell membrane potential to overshoot its dark resting value. This overshoot is associated with a large depolarizing synaptic potential in A-cells.6. An overshoot of the dark resting potential can also be elicited by the break of a hyperpolarizing pulse of current injected into an I-cell. The amplitude of this overshoot increases with pulse duration over a time course of seconds.7. In the presence of external tetraethylammonium ion (TEA) and tetrodotoxin, (TTX), the break of a hyperpolarizing pulse or the onset of a depolarizing pulse can evoke in an I-cell an action potential whose rate of rise and amplitude depend on the external Ca concentration. This action potential can be maintained by replacement of external Ca with Ba, or blocked by addition of 15 mm-Co to the saline. These observation's indicate that depolarizing potential changes in this cell activate a voltage-sensitive Ca conductance.8. When hyperpolarizing current pulses are injected into an I-cell, the voltage during the pulse sags back slowly towards the dark resting potential. Thus, during hyperpolarization with light or current an I-cell's membrane properties change over a time course of seconds.9. The onset of a depolarizing pulse or the offset of a hyperpolarizing pulse of current injected into an I-cell leads to a transient depolarization of a simultaneously impaled A-cell. Synaptic transmission occurs when the I-cell is depolarized to the vicinity of the dark resting potential. The amplitude of the response in an A-cell depends on the rate of change of the I-cell voltage.

Animals↗
PubMed1978

A potassium conductance activated by hyperpolarization in paramecium.

Voltage clamp studies show that the wild-type membrane of Paramecium tetraurelia contains a conductance component which is sensitive to hyperpolarization. This component manifests itself as "anomalous", or "inward going", rectification of membrane voltage in response to applied constant current pulses and as a "hyperpolarizing spike" when no K is added to the external solution (Y. Satow, C. Kung, 1977. J. Comp. Physiol. 119:99). Like the conductances which underlie anomalous rectification in other cells, the hyperpolarization-sensitive conductance in Paramecium is specific for K, and the magnitude of the voltage-dependent conductance change depends not only on voltage but also on external potassium concentration. The internal potassium ion concentration of Paramecium is calculated to be between 17 and 18mM.

Animals↗
PubMed1977

Separation of membrane currents using a Paramecium mutant.

The net membrane current of the electrically excitable membrane of Paramecium during step depolarisations was measured using voltage-clamp techniques. The mutant, pawn B, lacks a functional Ca channel. Thus the difference between the total current measured in the wild type and the leakage and rectification currents measured in the pawn mutant is the Ca current. These findings were confirmed by ion substitution experiments. The possibility that inactivation may be apparent only, and caused by a hypothetical, superposed, Ca-induced, rectifying K+ current was eliminated.

Animals↗
PubMed1976

Neural excitation of the larval firefly photocyte: slow depolarization possibly mediated by a cyclic nucleotide.

1. In firefly larvae, extracellular recordings from the light organ nerve show that a volley of action potentials elicits a glow of an intact animal. 2. Intracellular recordings from the photocytes show that they respond to nerve stimulation with a slow, graded depolarization which precedes light emission. The depolarization begins about 0-5 s after the nerve is stimulated; it peaks about 1 s after stimulation; and subsides about 2-5 s after the stimulus. The glow increases fastest when the photocyte depolarization is at its peak and lasts 5-15 s. 3. Photocyte depolarization is associated with a decrease in the input resistance of the cell. 4. Adrenergic receptors in the light organ are pharmacologically similar to vertebrate alpha-receptors. 5. Phophodiesterase inhbitors, aminophylline and theophylline, cause the light organ to glow, suggesting that cyclic nucleotides may mediate the effect of the adrenergic nerve transmitter.

Action Potentials↗
PubMed1975

Ultrastructure of the larval firefly light organ as related to control of light emission.

The firefly larva has a pair of light organs consisting of a layer of interdigitating, light emitting cells, covered dorsally with a layer of opaque, white cells. Each light organ is ventilated by one large and several smaller tracheal branches and is innervated by a branch of the segmental nerve containing two axons. These axons branch profusely in the photocyte layer so that several nerve profiles are seen around any photocyte. Nerve terminals contain large dense-core vesicles and small light-core vesicles. Clusters of light-core vesicles surrounding irregularly shaped membrane densifications, presumably the synapses between nerve and photocyte, are common in nerve terminals. Light emitting cells in insects characteristically contain photocyte vesicles. In the larva there are both full and empty photocyte vesicles; the full vesicles contain a matrix with tubular membrane invaginations in contrast to the empty vesicles which contain amorphous membrane invaginations.

Animals↗
PubMedDate not supplied

Role of biophysical specialization in cholinergic modulation in neurons of the ventral cochlear nuclei.

In contacting arrays of different types of neurons whose axons have differing targets in the brain stem, the auditory pathway is subdivided into parallel ascending pathways, each of which carries a different type of information. Several distinct arrays of neurons in the ventral cochlear nuclei have anatomical and biophysical specializations which enable them to extract differing facets of acoustic information and to convey it up the auditory pathway. T stellate cells have higher input resistances and have lower firing thresholds than bushy or octopus cells, enabling their firing to be modulated by small currents. Cholinergic currents, driven by neurons in the ventral nucleus of the trapezoid body that are likely to include medial olivocochlear efferents, excite T stellate cells, but have subtle effects on the firing of bushy cells, and have no detectable influence on octopus cells and D stellate cells. We suggest that cholinergic excitation of T stellate cells contributes toward shifting their acoustic dynamic ranges and increasing the encoding of spectral peaks in noisy conditions and in awake animals.

Acetylcholine↗