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At least 973 records · Page 54Linked to original sources
PubMed1991

[Pain in children: the mechanisms of transmission and response].

The pain transmission pathways are briefly reviewed, emphasizing the major role the endogenous opioid system plays as a modulator of the pain. The neuroanatomic and physiologic evolution of pain, both in fetus and newborns, are also stated, as well as its relationship with clinical and hormonal response to harmful stimulus. On the whole as newborns can perceive pain preventing this with anaesthetic agents reduces the surgical stress.

Afferent Pathways↗
PubMed1990

Input and output connections of an anteromedial group of spiking local interneurons in the metathoracic ganglion of the locust.

Intracellular recordings were made from an anteromedial group of spiking local interneurons in the metathoracic ganglion of the locust to determine the input connections that shape their mechanoreceptive fields on a hindleg and the output connections that define their effects on hindleg motor neurons. The receptive fields of these interneurons may contain excitatory and inhibitory regions. An excitatory region on the ipsilateral hind leg is formed by direct excitatory connections of the afferents from exteroceptors. Afferent spikes consistently evoke EPSPs in interneurons with a central synaptic latency of 1.2-1.5 msec. The connections appear to be direct and chemically mediated. An inhibitory region of a receptive field is not formed by direct afferent connections. Instead, spiking local interneurons of a midline group, which also receive direct excitatory inputs from the afferents, make direct inhibitory connections with anteromedial interneurons. Spikes in particular midline interneurons consistently evoke IPSPs in anteromedial interneurons with a central synaptic latency of about 1.0 msec. The connections appear to be direct and chemically mediated. By contrast, spikes in anteromedial interneurons could not be linked to any synaptic potentials in midline interneurons, so that direct connections are unidirectional and inhibitory. The large inhibitory regions to the receptive fields of anteromedial interneurons result from convergent inhibitory inputs of several midline interneurons. Each midline interneuron may make inhibitory output connections with several anteromedial interneurons, but there is a high degree of specificity in these divergent connections. Anteromedial interneurons make excitatory output connections with specific hind leg motor neurons. EPSPs in motor neurons follow spikes in the interneurons with short and consistent synaptic latencies of about 1.0 msec. The connections appear to be direct and chemically mediated. Two or more anteromedial interneurons with overlapping receptive fields may converge onto one motor neuron, and, in turn, one interneuron may make divergent connections with several motor neurons of the same pool. This pattern of connections suggests that these interneurons are essential elements in the local circuitry responsible for the expression of local reflexes of a leg. They provide an excitatory drive to the motor neurons in parallel to that from nonspiking local interneurons when particular arrays of exteroceptors are stimulated.

Action Potentials↗
PubMed1990

Distributed processing of sensory information in the leech. I. Input-output relations of the local bending reflex.

Sensory processing in the local bending reflex of the leech (Hirudo medicinalis) was studied by examining the input-output relations of the reflex. Sensory cells (P cells) were stimulated singly and in pairs and the responses of the longitudinal muscle motor neurons were recorded. Each pattern of single and paired P cell stimulation produced a unique pattern of motor neuron response. In general, motor neuron response patterns were consistent with the behavioral response of the whole animal.

Afferent Pathways↗
PubMed1988

The pretectal nuclear complex and the accessory optic system.

A critical survey of the nomenclatures used for subdivisions of the pretectal nuclear complex is followed by a description of pretectal development and connectivity of individual nuclei. Some of these mediate the pupillary light reflex; part of another forms part of the accessory optic system, involved in processing visual signals for the generation of compensatory (optokinetic) eye movements. The anatomy, development, connections and function of the accessory optic system and its subdivisions are reviewed.

Afferent Pathways↗
PubMedDate not supplied

[Neural control of somatic muscle function in the earthworm, Allobophora longa, and in the leech, Hirudo medicinalis].

Studies have been made on the electrical activity of the segmentary nerves and connectives of the abdominal nervous chain in the earthworm and leech. It was shown that the electrical activity of the isolated piece of the abdominal chain of the leech is manifested of periodic outbursts of impulsation. Presumably this central periodicity accounts for the discharge-like pattern of muscle rhythmic activity which was revealed in our earlier investigations. The electrical activity in the central nervous system of the earthworm depends on afferent influences which pass to the ganglia from the peripheral sensory nervous cells. Stimulation of the abdominal nervous chain did not result in extra discharges of muscle activity, but only affected some of the parameters of the latter.

Afferent Pathways↗
PubMed1978

[Pain relief during delivery by transcutaneous electrical nerve stimulation (author's transl)].

The analgesic effect of transcutaneous electrical nerve stimulation (TNS) during delivery has been evaluated. The usual technique of TNS was modified to suit the specific needs of pain control during the whole course of delivery. Two pairs of electrodes were taped to the patient's back, one pair level with the spinal processes Th 10-L1 and the other with S2-S4, corresponding to the influx of pain during the first and second stages respectively. Stimulation was delivered as biphasic pulses at 60-80 Hz. A low-intensity stimulation was given continuously, and a high-intensity stimulation was initiated by the patient herself whenever pain increased. As a rule, stimulation via the thoracic electrodes was given throughout delivery and sacral stimulation added from the later part of the first stage. No complications with respect to mother or child have occured. Three hundred and forty-seven women have been treated, 47% of them considered the analgesia with TNS to be good or very good, 42% experienced a certain effect whil 11% considered that TNS made no difference. In view of the relatively good results and the absence of complications, the authors recommend the method as a primary pain relieving measure to which conventional methods can be added if necessary.

Afferent Pathways↗
PubMed1983

Interaction of baroreflex bradycardia and inotropy in the rabbit.

In urethane-anaesthetized, closed-chest rabbits negative inotropic reflex responses from the left ventricle were elicited by aortic nerve (AoN) and carotid sinus nerve (CSN) stimulation in the paced and spontaneously beating heart and characterized as percent decrease of the contractility index (d log p/dt)max. The negative inotropic reflex action upon the left ventricle is, at freely changing heart rate, masked by the concomitant reflex bradycardia, in dependence on the prestimulation spontaneous heart rate. Therefore, inotropic reflex responses to AoN and CSN stimulation, as well as before and after vagotomy are comparable only on the condition of paced heart. In hearts with a prestimulation rate below 245 beats/min the negative reflex inotropy at freely changing rate is higher than under pacing, and at rates above 245 beats/min vice versa. It is assumed that at lower rates the nervous inotropy is augmented by negative rate-dependent inotropy (Bowditch staircase), at higher rates counteracted by a positive staircase, caused by reflex bradycardia. This nonuniform interaction can be explained by the strength-interval relation of the left ventricle which has an optimum at 245 ms (= 245 beats/min). The inotropic effect differences between stimulations at freely changing and paced heart rate are correlated to the effective heart intervals; the regression lines both for AoN and for CSN stimulation show equal intercepts with the abscissa at 245 ms. This is further evidence that at high heart rate the negative nervous inotropy counteracts, and at low rate cooperate with the rate-dependent inotropy.

Afferent Pathways↗
PubMed1983

[Pathways in the dorsomedial hippocampus of the turtle].

In tortoises (Testudo horsfieldi Gray) and in pond turtles (Emys orbicularis L.) rostral portions connections of the dorsomedial hippocamp with various structures of the forebrain and the diencephalon have been studied. Reciprocal connections of the hippocamp with the olfactory bulb have been revealed by means of the horseradish peroxidase method. Other olfactory centers of the hemisphere (anterior olfactory nucleus, olfactory tubercle, bandaletta diagonalis (Broca) nucleus and medial nucleus of the anterior amygdaloid area) send to the hippocamp their afferent fibres. An essential number of peroxidase-labelled cells are detected in the anterior thalamic, anterior dorsolateral and anterior dorsomedial nuclei (the lateral preoptic, the periventricular, the lateral and the mamillary (niclei) are labelled in less number. By means of the anteriograde axons and terminas degeneration, it has been stated that descending axons of the dorsomedial hippocamp terminate in the same nuclei of the dorsal thalamus, in which the labelled cells are revealed after injection of horseradish peroxidase into the hippocamp. The experiments demonstrate that there is a considerable prevalence of the hippocampal fibres descending to the thalamic nuclei comparing those descending to the hypothalamus. The results obtained demonstrate structural heterogeneity of the tortoise hippocamp. The data on connections of the tortoise three thalamic nuclei with the hippocamp make it possible to consider them as limbic structures.

Afferent Pathways↗
PubMed1981

An experimental study of early ultrastructural changes in the injured spinal cord.

Experimental hemisection injury of rat spinal cord was undertaken in order to examine Wallerian degeneration of ascending and descending tracts, and alterations in neurons and synapses. By light microscopy degeneration of axons was recognized first at 72 hours post-operatively. On the other hand, EM study revealed axonal degeneration 24 hours post-operatively. There were several ultrastructural changes in the early stages after hemisection injury. Increase in number of lysosomes in neurones was believed to be related to "autolysis" of the injured spinal cord. Another noteworthy finding was the "separation" of boutons. The mechanisms considered to account for these findings were deafferentation and oedema.

Afferent Pathways↗