Biomedical subjects

A Eblen-Zajjur

Publications and source records attributed to A Eblen-Zajjur.

5 recordsLinked to original sources

PubMed1997

PAG-microinjected dipyrone (metamizol) inhibits responses of spinal dorsal horn neurons to natural noxious stimulation in rats.

In addition to their well-known peripheral and spinal effects, non-steroidal antiinflammatory drugs (NSAIDs) are believed to diminish nociceptive responses by acting supraspinally and activating descending modulatory systems. We have herein investigated whether this descending action involves a depression of spinal sensory neurons. In rats under barbiturate anesthesia, responses of lumbar wide-dynamic-range neurons to a noxious clamp in their receptive fields were depressed to 46% of baseline value by the microinjection of 100 microg dipyrone (metamizol) into the periaqueductal gray matter (PAG). These results show that PAG application of NSAIDs activates descending systems which depress the excitation of spinal sensory neurons by natural noxious stimuli.

Animals↗

PubMed1997

A simple analog of visual field retinal projection.

Basic biophysical principles of the eye, such as the retinal projection of the visual field, bidimensional image inversion, blind point determination, visual field and retinal quadrants, perimetric principles, and determination of scotoma, are seen on a working anatomic model of the eye and its visual field that can easily be constructed at very low cost and from easily obtained materials: an opaque glass globe, a styrofoam hemisphere, a wood screen, bulbs, sockets, wire, and switches. This model has been used for many years in our undergraduate medical physiology courses and has replaced the classical model of candle image inversion by a converging lens.

Audiovisual Aids↗

PubMed1996

Fractal analysis of spinal dorsal horn neuron discharges by means of sequential fractal dimension D.

The present study describes a new method for converting a typical point process, such as a train of neuronal action potentials (spikes), into a planar curve which is then processed by means of a fast algorithm to calculate and display the fractal dimension D values of each of a sequence of blocks having an equal and preselectable number of interspike intervals, hence the term sequential fractal dimension D (SFD). This method is fast, does not require special computing facilities, and provides a continuous, high temporal resolution display of the neuronal discharge complexity along the course of spontaneous activity or event relating changes. The method affords insight into short duration changes in neuronal behaviour in a way independent of its discharge rate. SFD analysis of spike trains from spinal dorsal horn neurons suggests that the neuronal response to a given stimulus can be expressed as changes in the discharge pattern complexity, thus revealing a novel sensory coding strategy.

Action Potentials↗

PubMed1995

Differential effects of spinalization on discharge patterns and discharge rates of simultaneously recorded nociceptive and non-nociceptive spinal dorsal horn neurons.

Recordings were made simultaneously from 2-5 neurons at the same site in the lumbar spinal dorsal horn of pentobarbital-anesthetized rats. Neurons were classified as low-threshold (LT) or multireceptive (MR) according to their responses to non-noxious mechanical or noxious radiant heat stimuli of the skin. At the same recording sites neurons could be encountered which belong to different classes and/or which had mechanoreceptive fields which did not overlap. Cold blocks of the upper or lower thoracic cord or transsections of the upper cervical cord were made to evaluate the effects of spinalization on both the rate and pattern of background activity and/or noxious heat-evoked responses of different dorsal horn neurons under identical experimental conditions. At 24 of 27 recording sites, spinalization had qualitatively or quantitatively different effects on the rate of background activity of simultaneously recorded neurons. Interspike interval (ISI) means of background activity were significantly reduced in 29 of 65 (44.6%) neurons, prolonged in 23 of 65 (35.4%) neurons, or unchanged in 13 of 65 (20%) neurons. MR neurons displayed a significantly higher incidence of decreased background activity 17 of 45 (37.8%) and a lower incidence of increased background activity (18 of 45, 40%) during spinalization than the LT neurons from which 1 of 12 (8.3%) decreased and 8 of 12 (66.6%) increased background activity. Almost all (95.4%) neurons changed their discharge patterns after spinalization. At 9 of 27 recording sites, the discharge patterns of simultaneously recorded neurons were affected differently by spinalization as revealed by the coefficient of dispersion of the interspike intervals (ISI), indicating changes in the tendency to discharge action potential in clusters (bursts). At the same recording sites the level of noxious heat-evoked responses of simultaneously recorded MR neurons was also differentially affected by spinalization. Nociceptive responses were significantly enhanced in 19 of 37 (51.4%) neurons (137.8 +/- 142.6% of control, mean +/- SD), reduced in 13 of 37 neurons (35.1%) (by 58.9 +/- 20.9%) and/or unchanged in 5 of 37 (13.5%) neurons. It is concluded that no general 'tone' of descending antinociception exists and that tonic descending excitatory and inhibitory systems may be active simultaneously modulating both the level and pattern of neuronal discharges.

Animals↗

PubMed1995

Analysis of single and multiple neuronal discharges as point processes: a computer program set.

The analysis of single or multiple neuron discharges as point processes has gained considerable importance for understanding the principles of information coding and processing in the central nervous system (CNS). Here, a set of programs written in BASIC language for microcomputers is described for the point process analysis of discharges of individual or multiple simultaneously recorded neurons as well as the mathematical basis of the methods implemented in these programs. The input data consist of one or more ASCII files with the spike or stimulus occurrence times generated by the spike sorting system used. Interspike interval histogram, autocorrelogram, autospectrum, cross-correlogram, joint impulse configuration scatter diagram, poststimulus time histogram and joint peristimulus time scatter diagram, together with other more conventional methods, are included in this package which provides graphical or alpha numeric results which can be printed or stored on disk for additional graphical or statistical analysis.

Action Potentials↗