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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intramedullary or subarachnoid injections of alumina cream were made in the lumbar region of 38 adult cats. The animals were observed for 3 to 12 months and then subjected to acute neurophysiologic and histologic analysis. Neuronal hyperactivity in the dorsal horns was reliably produced by either subarachnoid or intramedullary alumina; behavioral abnormalities were not produced unless some of the alumina was present adjacent to dorsal root fibers in the subarachnoid space. Neuronal hyperactivity does not predict cutaneous hyperesthesia or motor abnormality; alumina produces scarring in the subarachnoid space and probably causes pain by making the dorsal root fibers mechanosensitive. Subarachnoid alumina may be a good model for human arachnoiditis.
Pain 1978 Oct
PMID:Intraspinal alumina injection: the relationship between epileptiform focus, root scarring and chronic pain. 10 60

Neuronal activity in the spinal trigeminal subnucleus oralis in response to electrical tooth stimulation was recorded in the anaesthetized cat in order to compare the electrophysiological characteristics of the oralis neurons with those of subnucleus caudalis and interpolaris neurons recorded in previous studies. The most sensitive oralis neurons had lower thresholds and shorter latencies than the most sensitive caudalis and interpolaris neurons. The thresholds of the oralis neurons were lower and their strength-duration curves flatter than those depicting liminal dental pain in man but similar to those depicting liminal jaw reflexes in the cat. Noxious conditioning stimulus elevated the threshold of only 1 of 10 neurons tested. The converging input from the skin and oral mucosa was from low-threshold mechanoreceptors. The results indicate that the response properties of the subnucleus oralis neurons differ significantly from those of other spinal subnuclei. Human pain thresholds cannot be explained by the liminal response properties of oralis neurons. These neurons might be important in the mediation of liminal reflex events evoked by dental stimuli.
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PMID:Response characteristics of tooth pulp-driven postsynaptic neurons in the spinal trigeminal subnucleus oralis of the cat. 157 51

Neuronal multiplication occurs mainly from the 10th to the 20th gestational weeks, after which probably no new nerve cells are formed, though neuronal arborization and the formation and re-organisation of synapses continues until adulthood. An intriguing question is how the blueprint for the formation of about 100 billion nerve cells and their dendrites and synapses can be contained in the human genome. Environmental factors are probably crucially involved in the development of the brain, particularly from the later stages of gestation onwards. Somatosensory functions are developed at an early stage. The pain threshold is assumed to be lower in the fetus than in the adult. In man, general fetal movements appear from the 8th gestational week, and more complex movements such as sucking, swallowing and breathing during the 10th-12th gestational weeks. These movements are generated by neuronal networks, and seem to occur spontaneously without any sensory stimulation. At birth there is a general excitation of the infant, and the neonate is awake and aroused. Studies in rats have shown a multifold increase in noradrenaline turnover to occur in the brain stem at birth, which is assumed to be related to the arousal of the newborn. Recent studies have shown that there is a switch-on of an excitatory neuropeptide genes at birth, and an increase in noradrenaline in the locus coeruleus which is assumed to be the arousal centre.
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PMID:[Functional development of the brain in the fetus and the newborn infant]. 194 96

A controversy exists concerning the role of the neuropeptide somatostatin for the transmission or inhibition of nociceptive information in the spinal cord. To better correlate electrophysiological effects of somatostatin at single cell level with results obtained with intrathecal injections of somatostatin in behaving animals and human pain patients we applied somatostatin to the spinal cord by controlled superfusion of the recording segment in vivo. The hypothesis of an opioid link and possible neurotoxic effects of somatostatin were also addressed. In cats deeply anaesthetized with pentobarbitone, halothane and nitrous oxide, extracellular recordings were made from 27 neurons located in laminae I-VI. All neurons responded to both innocuous mechanical and noxious radiant heat stimuli applied to the glabrous skin of the ipsilateral hindpaw. The dorsal surface of the spinal cord was superfused at the recording segment by means of a Perspex chamber (7 x 7 mm). Somatostatin superfusions at 1.2 microM had no effect on responses to noxious heat. Responses were, however, depressed by somatostatin at 61 microM to 59.7 +/- 5.1% of control and by somatostatin at 1.53 mM to 39.9 +/- 9.5% of control. This inhibition was not antagonized by the mu-opiate antagonist naloxone applied to the spinal cord at concentrations of 2.7 mM, either together with somatostatin, or after the inhibition by somatostatin had fully developed. Neuronal responses were linear functions of the skin temperatures for stimulation intensities between 42 degrees C and 52 degrees C. The slopes of these stimulus response functions were reduced during somatostatin superfusion at 61 microM to 46.8 +/- 9.3% of control, without changing the temperature thresholds for responding (42.5 +/- 0.6 degrees C). Somatostatin superfusion at 61 microM had no effect on the number of action potentials evoked by innocuous skin brushing, or by electrical stimulation of primary afferent A-fibres in cutaneous nerves. The amplitude of intraspinally recorded field potentials evoked by these electrical nerve stimuli was also unaffected by somatostatin. The inhibition of nociceptive spinal dorsal horn neurons by spinally administered morphine was assessed in eight experiments. Morphine reduced noxious heat-evoked responses to 42.1 +/- 9.6% of control at 0.3 mM and to 51.8 +/- 6.9% of control at 3.0 mM. The slopes of the stimulus-response functions were reduced by morphine at 0.3 mM to 53.1 +/- 11.3% of control, without changing the temperature thresholds (42.7 degrees C). Naloxone superfusion (2.7 mM) reliably antagonized the inhibition by morphine. Brush-evoked responses were not, or much less, affected by spinal morphine.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Spinal somatostatin superfusion in vivo affects activity of cat nociceptive dorsal horn neurons: comparison with spinal morphine. 197 67

Neuronal multiplication occurs mainly from the 10th to the 20th gestational weeks, after which probably no new nerve cells are formed, though neuronal arborisation and the formation and re-organisation of synapses continues until adulthood. An intriguing question is how the blueprint for the formation of about 100 billion nerve cells and their dendrites and synapses can be contained in the human genome. Environmental factors are probably crucially involved in the development of the brain, particularly from the later stages of gestation onwards. Somatosensory functions are developed at an early stage. The pain threshold is assumed to be lower in the fetus than in the adult. In man, general fetal movements appear from the 8th gestational week, and more complex movements such as sucking, swallowing and breathing during the 10th-12th gestational weeks. These movements are generated by neuronal networks, and seem to occur spontaneously without any sensory stimulation. At birth there is a general excitation of the infant, and the neonate is awake and aroused. Studies in rats have shown a multifold increase in noradrenaline turnover to occur in the brain stem at birth, which is assumed to be related to the arousal of the newborn. Recent studies have shown that there is a switch-on of various excitatory neuropeptide genes at birth, and an increase in noradrenaline in the locus coeruleus which is assumed to be the arousal centre.
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PMID:[Functional development of the brain in the fetus and the infant]. 205 60

The transplantation of chromaffin cells from the adrenal medulla into pain modulatory regions of the CNS has previously been shown to reduce pain sensitivity, most likely via local release of neuroactive substances from the transplanted cells. The ready availability of bovine adrenal glands, as well as the high levels of opioid peptides produced by their chromaffin cells, make these glands a potentially valuable donor source for antinociception studies. However, the success of these xenografts depends on their ability to survive and integrate within the host CNS. The aim of the present study was to assess host-graft relationships of bovine chromaffin cells transplanted to the rat CNS. We have found that isolated bovine chromaffin cells survive for at least three months in the rat periaqueductal grey, with no evidence of immunological response following a short-term course of immunosuppressant treatment. In the early stages following transplantation, only minor pathology is found at the injection site, which apparently recovers completely at later stages. The host-graft borders are not well demarcated, in contrast to solid tissue grafts. Neuronal processes of host origin, forming numerous synapses with the transplanted bovine chromaffin cells, are apparent by three weeks following transplantation. Migration also occurs from the graft into the host parenchyma, as evidenced by individual chromaffin cells found near host parenchymal blood vessels. The clusters of chromaffin cells found in the graft itself are generally not very vascular, in contrast to solid tissue grafts. The chromaffin cell clusters are surrounded by blood vessels of the non-fenestrated CNS type at the host-graft border. It is likely that the small size of the graft does not require extensive angiogenesis. The lack of fenestrated peripheral-type endothelial capillaries, normally seen in adrenal medullary tissue grafts, may contribute to the survival of these xenografts in the rat brain.
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PMID:Host-graft relationships of isolated bovine chromaffin cells in rat periaqueductal grey. 207 11

Experiments reported in this study have been performed in order to investigate cholinergic and GABA-ergic neurotransmitter systems and substance P in the realization of internal inhibition and pain reinforcement. This was accomplished during the elaboration of inhibitory and defensive conditioned reflexes to light flashes in alert, nonimmobilized rabbits. Present results together with a review of past research indicate that the cholinergic system is directly involved in transmitting the effects of pain reinforcement to neocortical neurons. Substance P, a neuropeptide, reduces the background activity of neocortical and hippocampal neurons and the response of cortical neurons to pain and positive conditioned stimuli. The cholinergic system and substance P exert a modulating effect on the elaboration of internal inhibition. Phenybut, a GABA derivative capable of penetrating the blood-brain barrier, enhances inhibitory hyperpolarization in the cerebral cortex and improves discrimination between the inhibitory and reinforcing light flashes. It appears, therefore, that the GABA-ergic system plays a leading part in the elaboration of internal inhibition. Neuronal activity and slow potential changes in response to positive conditioned and pain stimuli occur in the same direction after administering the preparations, and the dynamics of these changes is different from that in responses to inhibitory stimuli. It may be supposed on these grounds that the neurotransmitter and neuromodulator systems studied possess a considerable degree of plasticity.
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PMID:On neurotransmitter mechanisms of reinforcement and internal inhibition. 243 77

The measurement of cutaneous pain threshold using the Neuromod Selectra Model 7750 Transcutaneous Neuronal Electrical Stimulator is described. Pain threshold, measured in 520 healthy volunteers aged 5-105 years, increased with age. Consistent values were obtained in 22 healthy volunteers on three successive days. Pain threshold may be rapidly measured by this method which is potentially of value in the assessment of patients with neurological deficits.
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PMID:Age-associated change in pain threshold measured by transcutaneous neuronal electrical stimulation. 268 20

The midbrain periaqueductal gray is a functionally heterogeneous region which plays an important role in pain modulation. Despite the heterogeneity considerable controversy exists regarding the presence or absence of morphological subdivisions within the region. The present study was designed to evaluate the possibility of morphological subdivisions within the rat periaqueductal gray by using a statistical cluster analysis system. In addition both qualitative and quantitative data concerning neuronal size, shape, and density were obtained. On the basis of measurements of over 12,000 neurons in two planes of section, the mean neuronal length of cell bodies in this region was 14.82 microns and the mean neuronal area was 95.59 microns squared . The mean neuronal density was found to be 16,284 cells per mm3. Neuronal density decreased from rostral to caudal in the periaqueductal gray. The data obtained from cluster maps suggest the presence of four subdivisions within this midbrain region. The medial subdivision contains the smallest neurons and exhibits the lowest cell density. The dorsolateral and ventrolateral divisions contain the largest neurons while the dorsal division displays the highest packing density. These results are discussed in light of recent receptor binding and immunohistochemical studies of this region.
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PMID:The midbrain periaqueductal gray in the rat. I. Nuclear volume, cell number, density, orientation, and regional subdivisions. 404 95

Neurons of the rostral ventromedial medulla (RVM) have been implicated in the modulation of nociceptive transmission. In order to further analyze their role in pain behavior, we studied their activity while eliciting the tail flick reflex with noxious heat. Recording sites were regions in the RVM from which microstimulation (less than or equal to 10 microA, 400 mu sec, 50 Hz continuous pulse trains) inhibited the tail flick reflex. Extracellular unit activity and tail temperature were recorded, stored, and plotted with reference to either the time of tail flick or the time when the stimulating temperature reached 45 degrees C. Neuronal discharges were found to be either increased (on-cells), decreased (off-cells), or unchanged around the time of the tail flick. The decreases in discharge were more closely correlated with the tail flick behavior than with the temperature of the stimulus. These off-cells were located at sites of lowest threshold for tail flick inhibition and tended to be ventral to on-cells. We propose that off-cells must pause if the tail flick is to occur, and that this pausing allows the transmission of nociceptive input through spinal reflex loops.
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PMID:The activity of neurons in the rostral medulla of the rat during withdrawal from noxious heat. 631 12


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