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Results for “sensory function”

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PubMed1996

A simple systems approach to neural-immune communication.

The marine mollusc Aplysia californica is emerging as a useful model system to study neuralimmune communication at the mechanistic level because it has a well characterized nervous system that is easily accessible and it shares with mammals similar basic cellular defensive responses to wounded or non-self, i.e. the accumulation of defense cells (haemocytes) at the target site. Loose ligation of peripheral nerves in Aplysia induces a cellular defense response as evidenced by the accumulation of numerous haemocytes around the ligature. The excitability of nociceptive sensory neurons having axons close to the responding haemocytes is significantly increased. Haemocytes also accumulate at regions of axonal injury. The finding that human recombinant IL-1 beta can enhance the expression of injury-induced sensory hyperexcitability coupled with the detection of (ir)IL-1 in Aplysia haemolymph raises the interesting possibility that cytokines released from activated haemocytes attracted to an injured nerve or to a foreign body close to peripheral nerves may modulate nociceptive sensory function. The feasibility of using results from simple system such as Aplysia to formulate testable hypotheses in more complex systems is also discussed.

Animals↗

PubMed1995

Teeth and tooth nerves.

(1) Although our knowledge on teeth and tooth nerves has increased substantially during the past 25 years, several important issues remain to be fully elucidated. As a result of the work now going on at many laboratories over the world, we can expect exciting new findings and major break-throughs in these and other areas in a near future. (2) Dentin-like and enamel-like hard tissues evolved as components of the exoskeletal bony armor of early vertebrates, 500 million years ago, long before the first appearance of teeth. It is possible that teeth developed from tubercles (odontodes) in the bony armor. The presence of a canal system in the bony plates, of tubular dentin, of external pores in the enamel layer and of a link to the lateral line system promoted hypotheses that the bony plates and tooth precursors may have had a sensory function. The evolution of an efficient brain, of a head with paired sense organs and of toothed jaws concurred with a shift from a sessile filter-feeding life to active prey hunting. (3) The wide spectrum of feeding behaviors exhibited by modern vertebrates is reflected by a variety of dentition types. While the teeth are continuously renewed in toothed non-mammalian vertebrates, tooth turnover is highly restricted in mammals. As a rule, one set of primary teeth is replaced by one set of permanent teeth. Since teeth are richly innervated, the turnover necessitates a local neural plasticity. Another factor calling for a local plasticity is the relatively frequent occurrence of age-related and pathological dental changes. (4) Tooth development is initiated through interactions between the oral epithelium and underlying neural crest-derived mesenchymal cells. The interactions are mediated by cell surface molecules, extracellular matrix molecules and soluble molecules. The possibility that the initiating events might involve a neural component has been much discussed. With respect to mammals, the experimental evidence available does not support this hypothesis. In the teleost Tilapia mariae, on the other hand, tooth germ formation is interrupted, and tooth turnover ceases after local denervation. (5) Prospective dental nerves enter the jaws well before onset of tooth development. When a dental lamina has formed, a plexus of nerve branches is seen in the subepithelial mesenchyme. Shortly thereafter, specific branches to individual tooth primordia can be distinguished. In bud stage tooth germs, axon terminals surround the condensed mesenchyme and in cap stage primordia axons grow into the dental follicle.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1996

Optical design with the aid of a genetic algorithm.

Natural evolution is widely accepted as being the process underlying the design and optimization of the sensory functions of biological organisms. Using a genetic algorithm, this process is extended to the automatic optimization and design of optical systems, e.g. as used in astronomical telescopes. The results of this feasibility study indicate that various types of aberrations can be corrected quickly and simultaneously, even on small computers.

Algorithms↗

PubMed1983

An anatomical investigation of visual inputs to the cat orbital cortex.

The orbital region of the cortex in the cat is known to be involved in multimodal sensory functions. Visual afferent connections of this area have been investigated using the horseradish peroxidase technique. Our results demonstrate the existence of projections from ipsilateral thalamic nuclei essentially at the suprageniculate and magnocellular medial geniculate junction, well known to have multimodal physiological properties.

Afferent Pathways↗

PubMed1983

Serotoninergic fibers in dorsal roots of the spinal cord.

In the lumbar segment of the spinal cord, serotonin-containing nerve fibers are shown to connect the descending serotoninergic pathway of the intermediolateral column with the ipsilateral dorsal root. This may suggest that efferent serotoninergic fibers, originating from brainstem raphe nuclei, leave the spinal cord via the dorsal roots. However, when tryptophan pretreatment is employed in addition to a monoamine oxidase inhibitor, a limited number of yellow-fluorescing neurons can at times also be visualized in the dorsal ganglia. These could be the cell bodies of origin of at least some of the above-mentioned serotonin-containing nerve fibers, which would then have, at least in part, an afferent, sensory function. At present, therefore, the origin and function of this newly discovered serotoninergic pathway remains to be clarified.

Animals↗

PubMed1985

Autoradiographic localization of [3H]nicotine binding sites in the rat brain.

In vitro autoradiography was used to visualize [3H]nicotine binding sites in the rat brain. Labeling was densest in the interpeduncular nucleus and medial habenula but was also detected in thalamic nuclei, areas related to sensory function, the cerebral cortex, and molecular layer of the dentate gyrus. Specific binding was sparse in the hypothalamus and caudate-putamen, and not detected in Ammon's horn of the hippocampus or in the periaqueductal grey matter. These findings may relate to the distribution of nicotine's cerebral loci of action.

Animals↗

PubMed1989

Galanin-positive nerves of trigeminal origin innervate rat cerebral vessels.

(GAL)-positive nerve fibers in rat cerebral vessels were demonstrated by immunohistochemistry, and their origin in the trigeminal ganglia and pathway in the nasociliary nerve to the vessels was shown by retrograde tracer technique and nerve transection. Some fibres in the vertebrobasilar system appear to originate in extracranial sources. With the antiserum used only few GAL fibers could be seen in the vessels, mostly in the vertebrobasilar system. In neonatally sympathectomized animals a rich network could be visualized in most pial arteries - still particularly in the vertebrobasilar system - probably as a result of a diminished competition for nerve growth factor. No vasomotor effect of GAL could be detected in isolated segments of pial arteries, neither in normal nor in sympathectomized animals, which rules out a direct postsynaptic effect on vascular tone. GAL did not display prejunctional modulatory action on the adrenergic nerves present in the vascular preparations. A sensory function of GAL is discussed.

Adrenergic Fibers↗

PubMed1993

Substance P innervation of equine synovial membranes: joint differences and neural and nonneural receptor localizations.

Substance P (SP) immunocytochemistry and receptor autoradiography were used to define the innervation of the equine synovial membrane of joints equivalent to the wrist and knuckle of man. SP-immunoreactive fibers were mainly concentrated around blood vessels in the subsynovial layer, although not exclusively, while in the more distal joint, SP fibers were more frequently seen in the synovial surface layer. Iodinated SP receptor autoradiography studies revealed silver grain concentrations in the advential layer of blood vessels associated with the vasa vasorum, on the vascular endothelium and in the synovial surface. These findings suggest that SP has various sites of action within the synovial membrane, each of which may contribute both a sensory function and a different component of the inflammatory process to the joint.

Animals↗

PubMed1994

Relief of post-herpetic neuralgia with the N-methyl-D-aspartic acid receptor antagonist ketamine: a double-blind, cross-over comparison with morphine and placebo.

Pain and sensory thresholds were examined before and after intravenous administration of ketamine (0.15 mg/kg), morphine (0.075 mg/kg) or saline in 8 patients with post-herpetic neuralgia. A randomized, double-blind, cross-over study design was used. Post-herpetic neuralgia was associated with impaired sensory function, as shown by reduced tactile and warm sensation in the affected compared with the contralateral non-affected skin area. Neither ketamine nor morphine changed significantly the thresholds for warm, cold, heat pain or tactile sensation. However, ketamine normalized abnormal heat pain sensations in 4 patients, probably due to a central effect. Ketamine, but not morphine, produced significant relief of pain. Pain evoked by non-noxious stimulation of the skin (allodynia) was significantly inhibited by ketamine as well as by morphine. Wind-up-like pain (i.e., pain evoked by repeatedly pricking the affected skin area) was significantly inhibited by ketamine, but significantly aggravated by morphine. Side effects were observed in all the 8 patients after injection of ketamine and in 6 patients after injection of morphine. The present results support the hypothesis that the N-methyl-D-aspartic acid (NMDA) receptors are involved in the control of post-herpetic neuralgia including allodynia and wind-up-like pain. The NMDA receptors also may play a role in the modulation of thermal perception.

Aged↗

PubMed1986

Benzodiazepine receptors in the human spinal cord: a detailed anatomical and pharmacological study.

The anatomical distribution and pharmacological characteristics of benzodiazepine receptors in the human spinal cord were examined in four cases aged 20-41 years using in vitro autoradiography and biochemical assays of [3H]flunitrazepam binding. In all cases, the autoradiograms demonstrated that benzodiazepine receptors were distributed in a consistently similar fashion in the gray matter of the cervical, thoracic, lumbar and sacral regions of the human spinal cord. At all levels, the highest densities of benzodiazepine receptors were found to be localized within lamina II of the dorsal horn as defined on cytoarchitectonic, myeloarchitectonic and substance P immunocytochemical criteria. Within this lamina the receptors were concentrated mainly in its deeper, inner portion which lies immediately adjacent to lamina III, with some overlap dorsally into the outer segment of lamina II and ventrally into the adjacent region of lamina III. The lowest density of receptors was found in regions of laminae I, IV, VII and X; in particular, in lamina VII the lowest concentration of receptors was found in the dorsal nucleus of Clarke and the sacral parasympathetic nucleus. The remaining laminae of the spinal gray (laminae, V, VI, VIII and IX) showed a moderate density of receptors. Biochemical assays of membranes prepared from the lumbosacral cord indicated that these [3H]flunitrazepam binding sites have high affinity and have the pharmacological characteristics of the "central" Type II benzodiazepine receptor. These results show a high concentration of Type II benzodiazepine receptors in the substantia gelatinosa of the human spinal cord and suggest a possible role for these receptors in spinal sensory functions.

Adult↗

PubMed1990

GABA, GABA receptors and benzodiazepine receptors in the human spinal cord: an autoradiographic and immunohistochemical study at the light and electron microscopic levels.

The regional, cellular and subcellular distribution of GABA, GABA receptors and benzodiazepine receptors was investigated by light and electron microscopy in the human lumbar spinal cord taken post-mortem from eight cases aged 20-76 years. Firstly, the regional distribution of GABA receptors and benzodiazepine receptors was studied using autoradiography following in vitro labelling of cryostat sections with tritiated ligands. This was followed by a detailed study of the cellular and subcellular distribution and localization of GABA and benzodiazepine/GABAA receptors by light and electron microscopy using immunohistochemical techniques with monoclonal antibodies to GABA and to the alpha and beta subunits of the benzodiazepine/GABAA receptor complex. The results showed a close correspondence in the regional distributions of GABA, GABA (GABAA and GABAB) receptors and benzodiazepine receptors. The highest density of GABA-like immunoreactivity, GABA receptors and benzodiazepine receptors was localized as a dense band within lamina II of the dorsal horn (especially inner lamina II) with moderately high densities in laminae I and III. The remaining laminae of the spinal gray matter showed much lower levels of labelling. A close correspondence was also seen in the distribution of GABA-like immunoreactivity and of benzodiazepine/GABAA receptor immunoreactivity at the cellular and subcellular levels. At the cellular level, the greatest number of GABA-immunoreactive cells was found in lamina II; they comprised small, round to oval cells and, on the basis of soma size, shape, orientation and dendromorphology, they corresponded to previously described islet and filamentous cells. Benzodiazepine/GABAA receptor immunoreactivity was also localized on the same cell types in lamina II. At the subcellular level in lamina II, GABA-immunoreactive axon terminals mainly established axodendritic synaptic contacts. Small numbers of GABA-immunoreactive axon terminals appear to form possible axo-axonic contacts in complex synaptic arrays. Benzodiazepine/GABAA receptors were localized within the same types of synaptic complexes in which GABA-immunoreactive axon terminals were found. In these synaptic complexes, benzodiazepine/GABAA receptor immunoreactivity was associated with presynaptic and postsynaptic membranes and on apparent non-synaptic membranes. These results show a high concentration of GABA, GABA receptors and benzodiazepine receptors in lamina II of the dorsal horn of the human spinal cord and suggest a possible role for GABA in spinal sensory functions.

Autoradiography↗

PubMed1993

Nitric oxide synthase immunoreactivity in the rat, mouse, cat and squirrel monkey spinal cord.

The distribution of nitric oxide synthase-immunoreactive neurons was examined in the spinal cord of rats, mice, cats and squirrel monkeys at the light microscopic level. Some sections were processed for choline acetyltransferase immunoreactivity. Double-labeling techniques were used to assess possible co-localization of nitric oxide synthase and choline acetyltransferase immunoreactivity in the same spinal neurons. Nitric oxide synthase-immunoreactive neurons were concentrated in three fairly well-defined regions of the spinal cord of all species studied: (i) the intermediolateral cell column of the thoracic and sacral segments, (ii) lamina X of all segments, and (iii) the superficial layers of the dorsal horn of all segments. A few nitric oxide synthase-immunoreactive neurons were scattered in the deeper laminae and the ventral horn. There were fewer nitric oxide synthase-positive neurons in monkey spinal lamina X and dorsal horn than in similar locations of rodents and felines. Double-staining showed that not all choline acetyltransferase-positive neurons in the intermediate cell column and lamina X were nitric oxide synthase-immunoreactive. In the ventral horn, choline acetyltransferase-positive neurons (presumed motoneurons) were nitric oxide synthase-negative. In addition to cell bodies, nitric oxide synthase-positive fibers were scattered in the dorsal, lateral and ventral horns of all species. Finally, punctate nitric oxide synthase-immunoreactive fibers were seen traversing the dorsal, lateral and ventral white matter, and reaching the respective gray matter. The present study shows that, in spite of quantitative differences, the pattern of distribution of nitric oxide synthase-positive neurons in the spinal cord was similar across the four species. The concentration of nitric oxide synthase-positive neurons in the autonomic nuclei and laminae I, II and X of all four species underscores a prominent role of these neurons in visceral and sensory functions.

Amino Acid Oxidoreductases↗

PubMed1995

The effects of dopamine and serotonin on rat dorsal root ganglion neurons: an intracellular study.

The effects of bath application of dopamine and serotonin (10(-10)-10(-8) M) were studied in the superfused dorsal root ganglia of 30-36-day-old rats by means of the intracellular technique. In the majority of cells, dopamine and serotonin caused depolarization (60% and 64% of the tested cells, respectively). In other cells hyperpolarization, biphasic reactions or absence of responses have been observed. All reactions were dose dependent and reversible. Depolarization was accompanied by a decrease of input membrane resistance and hyperpolarization by its increase. Some cells did not show these alterations. Monoamines were also capable of modulating spikes. In some cases dopamine (10(-8)-10(-7) M) decreased the amplitude of the action potential and increased its duration, but the same concentration of serotonin produced the opposite effect on these parameters. The correlation between the electrophysiological properties of the dorsal root ganglion neurons and their responses to monoamines were discovered. Neurons with high input membrane resistance, prolonged action potential and slow conduction velocity (small cells) were influenced much more by monoamines than neurons with low input membrane resistance, "fast" action potential and rapid conduction velocity (large cells). (1) Small cells had lower threshold to monoamines (10(-8)-10(7) M) than large ones, some of which did not respond even to 10(-6) M. (2) The amplitude and duration of monoamine-induced depolarization in small cells were on average about two to three times higher than those in large cells. These data provide evidence for the modulatory role of monoamines in spinal afferent sensory functions.

Action Potentials↗

PubMed1992

Pathology of radiation injury to the canine spinal cord.

The histopathologic response of the canine spinal cord to fractionated doses of radiation was investigated. Forty-two dogs received 0, 44, 52, 60, or 68 Gy in 4 Gy fractions to the thoracic spinal cord. Dogs were evaluated for neurologic signs and were observed for 1 or 2 years after irradiation. Six major lesion types were observed; five in the irradiated spinal cord and one in irradiated dorsal root ganglia. The three most severe spinal cord lesions were white matter necrosis, massive hemorrhage, and segmental parenchymal atrophy which had an ED50 of 56.9 Gy (51.3-63.3 Gy 95% CI) in 4 Gy fractions. These lesions were consistently associated with abnormal neurologic signs. Radiation damage to the vasculature was the most likely cause of these three lesions. The two less severe spinal cord lesions were focal fiber loss, which had an ED50 of 49.5 Gy (44.8-53.6 Gy 95% CI) in 4 gy fractions and scattered white matter vacuolation that occurred at all doses. These less severe lesions were not consistently associated with neurologic signs and indicated the presence of residual damage that may occur after lower doses of radiation. Radiation damage to glial cells, axons, and/or vasculature were possible causes of these lesions. In the irradiated dorsal root ganglia, affected sensory neurons contained large intracytoplasmic vacuoles, and there was loss of neurons and satellite cells. Such alterations could affect sensory function. The dog is a good model for spinal cord irradiation studies as tolerance doses for lesions causing clinical signs are close to the estimated tolerance doses for humans, and studies involving volume and long-term observation can be done.

Animals↗

PubMed1993

Expression of dopamine by chick primary sensory neurons and their related targets.

The expression of dopamine by primary sensory neurons and their peripheral projections was studied in the chick dorsal root ganglion by means of immunocytochemical procedures. Within the sensory neurons, dopamine immunoreactivity is first expressed by 0.8% of cells at E10 and reaches a percentage of 5.6% before hatching. After hatching, 8.6% of neurons, belonging to both the A and B classes of sensory neurons, exhibit a clear immunostaining. According to the immunostaining of nerve terminals located in various peripheral target tissues, these immunoreactive neurons are responsible, at least in part, for the sensory innervation of the skin and paravertebral ganglia. The results provide evidence that different classic neurotransmitters may be expressed by specific subpopulations of primary sensory neurons expressing various somatic and autonomic sensory functions in relation to specific targets.

Animals↗

PubMed1993

The relationship between auditory brainstem response and behavioral thresholds in normal hearing infants and adults.

The nature of age-related improvements in auditory sensitivity was explored by comparing behavioral and auditory brainstem response (ABR) thresholds in 3- and 6-month-old infants and in adults. Thresholds were estimated for tone pips at 1, 4, and 8 kHz, presented at a rate of 13.3/s. The time course of development of the two response measures was compared, and the correlation between thresholds for individual subjects was examined. Infant ABR threshold was adultlike at all frequencies, even among 3-month-olds. Infant behavioral thresholds were elevated relative to adult thresholds. Between 3 and 6 months, significant improvement occurred in the 8-kHz behavioral threshold, but no improvement occurred at other frequencies. This difference between ABR and behavioral measures in developmental time course suggests that peripheral sensitivity is not a major determinant of behavioral threshold elevation during infancy. The correlation between behavioral and ABR thresholds was significant at 4 kHz for 3-month-olds and at 8 kHz for adults. This suggests that variability in sensory function at these frequencies contributes to both behavioral and ABR thresholds, although other factors are likely to be involved as well.

Acoustic Stimulation↗

PubMed1995

Spinal cord concussion in previously undiagnosed osteogenesis imperfecta.

An 11-year-old boy was a victim of a motor vehicle accident. He initially presented with paraplegia and inability to detect pain below the fourth thoracic dermatome. Two hours later, he had full return of motor and sensory function. Thoracolumbar spine radiography and magnetic resonance imaging (MRI) showed multiple compression fractures and marked osteopenia of the vertebrae. The patient's family history is significant for osteogenesis imperfecta (OI), although the patient had not been previously diagnosed with this disorder. Although the patient had no prior fractures or any of the classic stigmata of OI except for short stature, plain radiographic and MRI findings in conjunction with his family history support the diagnosis of OI. A brief discussion of both OI and spinal cord concussion is presented.

Accidents, Traffic↗

PubMedDate not supplied

Nontraumatic abdominal aortic thrombosis presenting with anterior spinal artery syndrome and pulmonary edema.

A 51-year-old woman with a history of breast cancer developed pulmonary edema and lower extremity paraplegia with preservation of proprioception as the initial manifestation of abdominal aortic thrombosis. Back pain was present in the lumbar region radiating to buttocks and legs in a bilateral radicular pattern. Femoral pulses were initially palpable. Aortic angiography revealed complete abdominal aortic occlusion at L3 as well as total occlusion of the bilateral superficial femoral arteries and bilateral common iliac arteries. Transient occlusion of the anterior spinal artery due to aortic thrombosis may cause paraplegia and may also progress to renal failure, bowel infarction, and limb loss if left untreated. Abdominal aortic thrombosis needs to be considered in a patient who presents with an anterior spinal artery syndrome, which, if present, must be treated as rapidly as possible to preserve motor and sensory function.

Aorta, Abdominal↗