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PubMed2000

Abnormal visceral perception in patients with functional dyspepsia: use of cerebral potentials evoked by electrical stimulation of the oesophagus.

Altered visceral perception is thought to be included in the pathogenesis of functional dyspepsia. However, in previous studies, the assessment of visceral perception has been based solely on patients self-reported symptoms. Cerebral evoked potential (EP), either by mechanical or electrical stimulation (ES) of the visceral organ, is used to evaluate visceral perception via afferent neural pathways. In this study, we investigated the visceral perception in patients with functional dyspepsia by EP to eliminate the possibility of self-reported bias. EP responses were recorded by oesophageal ES at 37 cm from the nostril in 14 patients with functional dyspepsia and 14 normal healthy control subjects. Threshold levels of perception, peak latencies and peak-to-peak amplitudes of EP were evaluated. There was no difference in the sensory threshold between the dyspeptic patients and the control subjects (median 6 mA, range 2-12 mA, vs. 8 mA, range 6-14 mA; P= 0.09). There was a strong trend towards a decreased discomfort threshold in the patients when compared to the control subjects (median 14 mA, range 6-24 mA vs. 20 mA, range 14-26 mA; P = 0.05). The latency of the later EP peak (N2) among the patients (154 ¿ 4 ms) was significantly shorter than that of the control subjects (171 ¿ 3 ms, P < 0.01) although there was no difference between the earlier peaks (Ni and P1). There was also no difference in the amplitudes (Ni/Pi and P1/N2) of EP between the patients and the control subjects. Half of the patients (seven out of 14) complained of nausea during ES but the control subjects were unaffected. The latency of the first EP peak (Ni) in the patients with nausea was significantly shorter (66 ¿ 3 ms) than that of the patients without nausea (79 ¿ 4 ms, P 0.05) or among the control subjects (80 ¿ 3 ms, P < 0.05). These results suggest that dyspeptic patients may recruit a greater number of fast conducting myelinated nerve fibres that convey visceral afferent impulses to the brain and/or that dyspeptic patients may have an altered central processing of the visceral perception. We conclude that EP recording by oesophageal ES provides an objective measurement of altered visceral perception in patients with functional dyspepsia.

Adolescent↗

PubMed1990

Contralateral trigeminal dysaesthesias associated with second cervical nerve compression: a case report.

This 70-year-old woman presented with a left C2 solitary metastatic lesion producing ipsilateral occipital pain associated with contralateral fronto-orbital dysaesthesias. Examination revealed analgesia in the left C2 dermatome and hyperaesthesia in the right forehead. These symptoms and findings resolved following a course of radiation therapy to the C2 metastasis. Ipsilateral trigeminal dysaesthesias produced by cervical lesions have been described, however, contralateral cervicogenic trigeminal dysaesthesias have not. Relevant experimental data are analysed; neural pathways are suggested by which a cervical lesion, especially at C2 or C3, may produce trigeminal dysaesthesias referred ipsilaterally or contralaterally.

Aged↗

PubMed1993

The nociceptive flexion reflex as a tool for exploring pain control systems in headache and other pain syndromes.

The authors review the neural pathways mediating nociceptive flexion reflexes, the method for analyzing these reflexes in human beings, and available data on their modulation by supraspinal, opioid as well as serotonergic systems. They present results of studies of the biceps femoris flexion reflex (RIII) in pain syndromes and various types of headache. Nociceptive flexor reflexes appear to be interesting for studying the pathophysiology of head pain mechanisms and possibly for evaluating analgesic treatment.

Endorphins↗

PubMed2006

Role of the olfactory systems and importance of learning in the ewes' response to rams or their odors.

In sheep, exposure of seasonally anestrous females to the male or its fleece results in activation of luteinizing hormone (LH) secretion and synchronized ovulation. The study of the neural pathways involved in this phenomenon, commonly named "male effect", show that the main olfactory system plays a critical role in the detection and the integration of the male odor. The accessory olfactory system participates in the perception of the ram odor but does not seem necessary for the endocrine response. According to the hypothesis that the neuroanatomical differences between the two olfactory systems could be associated with different functional roles, we investigated the importance of sexual experience and learning processes in the male effect. Our results showed that female responses depend on previous sexual experience. We also demonstrated that the LH response to male odor could result from an associative learning process. The aim of the present report was to summarize our current knowledge concerning the "male effect" and in particular to clarify the role of sexual experience and learning in the processes involved in this effect.

Animals↗

PubMed2002

Radiofrequency procedures in chronic pain.

Radiofrequency current is simply a tool used for creating discrete thermal lesions in neural pathways in order to interrupt transmission. In pain medicine, radiofrequency lesions have been used to interrupt nociceptive pathways at various sites. This is a palliative treatment not without complications, so its use should be limited to those patients with cancer pain or chronic non-cancer pain for whom conservative non-surgical therapies have been ineffective or intolerable. With the development of alternatives such as intrathecal opioid infusion and neuromodulation technologies, the number of patients considered for neuroablative therapy may dwindle. Nevertheless, there is evidence that radiofrequency neurotomy has an important role in the management of trigeminal neuralgia, nerve root avulsion and spinal pain. In this chapter the evidence for efficacy and safety is reviewed and interrogated with special emphasis on the available randomized controlled trails and systematic review.

Catheter Ablation↗

PubMed1996

Distinct 5-HT receptors mediate the peristaltic reflex induced by mucosal stimuli in human and guinea pig intestine.

BACKGROUND & AIMS: The role of 5-hydroxytryptamine (5-HT) in regulating the peristaltic reflex in humans is unknown. The neural pathways subserving peristalsis induced by mucosal stimulation were characterized in human jejunum and guinea pig colon. METHODS: Compartmented flat-sheet preparations that enable measurement of 5-HT and sensory transmitter release into one compartment and mechanical responses in adjacent compartments were used. RESULTS: Mucosal stimuli (2-8 brush strokes) caused concomitant release of 5-HT and calcitonin gene-related peptide (CGRP) into the compartment where stimulation was applied in both species; in contrast, muscle stretch caused release of CGRP only. CGRP release as well as ascending contraction and descending relaxation of circular muscle induced by mucosal stimulation were inhibited by a selective 5-HT4 antagonist in human jejunum and by selective 5-HT4 and 5-HT3 antagonists in guinea pig colon. The effects of the 5-HT3 and 5-HT4 antagonists in guinea pig colon were additive. A selective 5-HT1P antagonist mimicked the effect of the 5-HT4 antagonist. The CGRP antagonist human CGRP8-37 inhibited ascending and descending responses in both species. CONCLUSIONS: 5-HT released by mucosal stimulation initiates a peristaltic reflex by activating 5-HT4/5-HT1P receptors on sensory CGRP neurons in human intestine and 5-HT4/5-HT1P and 5-HT3 receptors in guinea pig colon.

Animals↗

PubMed1997

Colonic and jejunal motor disturbances after colonic antigen challenge of sensitized rat.

BACKGROUND & AIMS: Inflammation in the colon may alter motility in the proximal gut and potentiate clinical symptoms. The aim of this study was to characterize the effect of colonic anaphylaxis on local (colonic) and remote (small intestinal) motility and identify the mechanism and mediators involved. METHODS: Rats were sensitized by intraperitoneal injection of 10 microg egg albumin and surgically prepared with electrodes in jejunum and colon and a colostomy tube. Colonic and jejunal myoelectric activity were recorded in fasted animals before and after colonic antigen challenge without and then after pretreatment with specific antagonists. RESULTS: Colonic antigen challenge of sensitized rats was associated with significant (1) increase in colonic myoelectric spike activity, (2) disruption of fasting jejunal motility and initiation of aborally propagating spike complexes, and (3) increase in plasma rat mast cell protease II levels with a decrease in granulated mast cells in colon but not jejunum. The myoelectric disturbance in both colon and jejunum was inhibited significantly by pretreatment with atropine and hexamethonium, doxantrazole, cyclooxygenase, and lipoxygenase inhibitors. Methysergide inhibited only the jejunal disturbance. CONCLUSIONS: Colonic antigen challenge of sensitized animals results in local mast cell activation and the release of mediators that modulate neural pathways to initiate both a local colonic and a remote jejunal myoelectric disturbance.

Albumins↗

PubMed2000

Expression of one group of genes maintains one unit of long-term memory in a brain model.

In a brain model, a unit of long-term memory is stored in the encoding synapses of a neuron as a presynaptic axonal 'on-off' pattern through the establishment of long-term potentiation (LTP) and long-term depression (LTD). Repetitive activation of one presynaptic axonal 'on-off' pattern speeds up the subsequent re-activation of the same pattern by inducing expression of a corresponding group of genes in support of the enzymes, protein substrates, and second messengers for the LTP and LTD that encode the unit of long-term memory. Phantom limb pains are memorized and re-activated through the expression of the corresponding group of genes, and re-experiencing the stressful event in post traumatic stress syndrome results from the expression of another group of genes. The sense of requiring less time to experience the content of a successfully retrieved long-term memory reflects an increased speed of re-activating the presynaptic axonal 'on-off' patterns of the memory, or an increased speed of thinking. Giving rise to a sense of familiarity with new things, déjà vu may also be a mental state with increased speed of thinking. The speed of thinking may be decreased in jamais vu that is opposite to déjà vu. Progressive increases in the speed of thinking when engaging in a hobby may open up a previously unused neural pathway that turns a previously happy feeling into an aversive one.

Gene Expression↗

PubMed2001

'Sensitivity syndromes' related to radiation exposures.

The primary health effects of radiation are traditionally believed to result from cellular genetic damage. These effects are believed to result in a statistically detectable increase in the induction of cancer in exposed populations. A significant number of residents of areas affected by the Chernobyl disaster and workers involved in the clean-up ('liquidators') have reported debilitating physical illnesses that cannot be easily explained by a genetic effect. This paper presents results of a literature search that strongly suggests that a previously unrecognized neural pathway may be responsible for the induction of these debilities. In addition, a common link between radiation and chemical sensitivity syndromes may now be identified.

Humans↗

PubMed1991

[Cerebral monitoring].

Several studies have shown that most anaesthesia-related critical incidents are due to human error. There is evidence that cerebral monitoring procedures may be of value for an early detection of cerebral hypoxia or ischaemia. Monitoring of central nervous physiology includes both evaluation of systemic parameters like arterial blood pressure, arterial PO2, PCO2, and temperature, and more specific parameters for the assessment of central nervous system function and intracranial haemodynamics. It has been suggested that parameters from the processed EEG may be used as an indicator for depth of anaesthesia. Even though anaesthetic-induced EEG alterations are unspecific, depth of anaesthesia may be assessed quantitatively by combined monitoring of general parameters and processed EEG. Interpretation of the EEG signals has to take into account that critical events like hypoxia or cerebral ischaemia results in EEG patterns similar to those seen under deep anaesthesia. Sensory evoked potentials are frequently used to monitor specific neural pathways that are at risk during surgery. Different pathways may be tested using different trigger modalities (somatosensory, auditory, visual). Changes in latencies and amplitudes of primary components may indicate impaired conduction in the pathway monitored. For operations in which monitoring of evoked responses is indicated, the anaesthetic technique should have minimal impact on latencies and amplitudes. In patients, cerebral blood flow can be monitored only at discrete time intervals. In contrast, non-invasive transcranial Doppler sonography may provide continuous information on intracranial haemodynamics. Relative changes in cerebral blood flow velocity have been shown to correlate closely to changes in cerebral blood flow. Cerebral perfusion pressure can be calculated by monitoring of intracranial pressure in patients with compromised intracranial compliance.

Anesthesia↗

PubMed1988

Evidence of an altered pattern of breathing during exercise in recipients of heart-lung transplants.

Recipients of heart-lung transplants represent an unusual opportunity to study the regulation of ventilation, because the neural pathways between the lungs and the central nervous system are disrupted in these patients. We compared the ventilation response in seven recipients of heart-lung transplants who had normal pulmonary function and seven recipients of heart transplants, all of whom performed incremental bicycle ergometry. The level of ventilation in recipients of heart-lung transplants was similar to that in heart-transplant recipients for equivalent levels of carbon dioxide production. Arterial pH and partial pressure of carbon dioxide at maximal exercise were normal and not significantly different in the two groups, also suggesting that levels of ventilation were appropriate in both groups. However, the rate of the rise in respiratory rate for increasing levels of ventilation was significantly lower in recipients of heart-lung transplants than in heart-transplant recipients, and the initial increase in tidal volume was more rapid in the former group than in the latter. Thus, recipients of heart-lung transplants have an appropriate level of ventilation during exercise as the result of a disproportionate increase in tidal volume at a reduced respiratory rate. We speculate that intrapulmonary receptors are important in regulating the pattern, but not the absolute level, of ventilation during exercise.

Acid-Base Equilibrium↗

PubMed2000

Neurophysiologic response to intraoperative lumbosacral spinal manipulation.

BACKGROUND: Although the mechanisms of spinal manipulation are poorly understood, the clinical effects are thought to be related to mechanical, neurophysiologic, and reflexogenic processes. Animal studies have identified mechanosensitive afferents in animals, and clinical studies in human beings have measured neuromuscular responses to spinal manipulation. Few, if any, studies have identified the basic neurophysiologic mechanisms of spinal manipulation in human beings or animals. OBJECTIVES: The purpose of this clinical investigation was to determine the feasibility of obtaining intraoperative neurophysiologic recordings and to quantify mixed-nerve root action potentials in response to lumbosacral spinal manipulation in a human subject undergoing lumbar spinal surgery. METHODS: An L4-L5 laminectomy was performed in a 62-year-old man. Short-duration (<0.1 ms) mechanical force, manually assisted spinal manipulative thrusts (150 N) were delivered to the lumbosacral spine with an Activator II Adjusting Instrument. With the spine exposed, spinal manipulative thrusts were delivered internally to the L5 mammillary process, L5-S1 joint, and the sacral base with various force vectors. This protocol was repeated by contacting the skin overlying respective anatomic landmarks. Mixed-nerve root recordings were obtained from gas-sterilized platinum bipolar hooked electrodes attached to the S1 nerve root at the level of the dorsal root ganglion during the spinal manipulative thrusts and during a 30-second baseline period during which no spinal manipulative thrusts were applied. RESULTS: During the active trials, mixed-nerve root action potentials were observed in response to both internal and external spinal manipulative thrusts. Differences in the amplitude and discharge frequency were noted in response to varying segmental contact points and force vectors, and similarities were noted for internally and externally applied spinal manipulative thrusts. Amplitudes of mixed-nerve root action potentials ranged from 200 to 2600 mV for internal thrusts and 800 to 3500 mV for external thrusts. CONCLUSIONS: Monitoring mixed-nerve root discharges in response to spinal manipulative thrusts in vivo in human subjects undergoing lumbar surgery is feasible. Neurophysiologic responses appeared sensitive to the contact point and applied force vector of the spinal manipulative thrust. Further study of the neurophysiologic mechanisms of spinal manipulation in humans and animals is needed to more precisely identify the mechanisms and neural pathways involved.

Action Potentials↗

PubMed2001

Are human milk long-chain polyunsaturated fatty acids related to visual and neural development in breast-fed term infants?

OBJECTIVE: To determine whether docosahexaenoic acid (DHA) is related to visual and neural development in term breast-fed infants. DESIGN: A prospective study of 83 infants who were exclusively breast-fed for at least 3 months. We determined red blood cell and plasma fatty acids at 2 months, visual acuity at 2, 4, 6, and 12 months, speech perception and an object search task at 9 months, Bayley's mental development index and psychomotor development index at 6 and 12 months, and novelty pReference at 6 and 9 months. RESULTS: The infant red blood cell phosphatidylethanolamine DHA was significantly related to visual acuity at 2 months of age (r = 0.32, P =.01) and 12 months of age (r = 0.30, P =.03). The ability to discriminate nonnative retroflex and phonetic contrasts at 9 months of age was related to the plasma phospholipid DHA (r = 0.48, P <.02) and red blood cell phosphatidylethanolamine DHA (r = 0.26, P =.02) at 2 months of age after adjusting for covariates. CONCLUSION: DHA may influence the development of visual acuity and neural pathways associated with the developmental progression of language acquisition in term breast-fed infants. The extent to which our results can be attributed solely to DHA from maternal sources through breast milk or in gestation or other confounding factors remains to be determined.

Breast Feeding↗

PubMed1998

Energy balance and ovulation: small cages versus natural habitats.

In the laboratory, ovulation is suppressed when a mammal is in negative energy balance whether that state is caused by inadequate food intake, excessive locomotor activity or heavy thermoregulatory costs. In this paper, knowledge generated in the laboratory about the link between ovulation and energy balance is examined in relation to the kinds of energetic challenges mammals actually face in natural habitats. When viewed in that context, several conclusions can be drawn. First, females ovulate whenever extant energetic conditions permit unless the process is blocked by non-metabolic stress, social cues or a predictive seasonal cue such as photoperiod. In the latter case, most mammals show at least a seasonal tendency in their reproduction and the majority do not use a predictive cue; they reproduce opportunistically in relation to seasonal variation in the energetic characteristics of their environment. Second, the widely held assumption that a female's fat reserves must exceed a critical level in order that she may ovulate finds no support in the literature dealing with natural populations. Third, the surprisingly rapid responsiveness of the gonadotrophin releasing hormone (GnRH) pulse generator to energetic manipulation probably reflects the study of animals that are in a pure survival mode. Fourth, the complexity of the energetic challenges mammals face in the wild suggests that there are probably multiple metabolic and neural pathways coupling ovulation to energy balance and that these pathways are probably characterized by considerable overlap and redundancy. Thus, fifth, to develop a more realistic overview of these pathways there is a need for experimental designs that present mammals with the kinds of complex challenges they actually face in the wild habitats in which they evolved.

Adipose Tissue↗

PubMed1991

Neurophysiological control of the secretion of gonadotrophin-releasing hormone and luteinizing hormone in the sheep--a review.

The anterior pituitary gland secretes pulses of luteinizing hormone (LH) in response to pulses of gonadotrophin-releasing hormone (GnRH) released into the hypophysial portal blood by the hypothalamus. The pulsatile nature of the secretions is very important because the frequency of the pulses is directly related to the activity of the GnRH neurons. We can therefore take advantage of this phenomenon to develop mechanistic interpretations of responses to experimental treatments designed to unravel the neural pathways that influence what is, arguably, the most important individual signal controlling the activity of the reproductive system. We might also resolve the disagreements in the literature covering the neuropharmacology of gonadotrophin secretion. In this review, we describe work towards this end in the sheep. Most (95%) of the 2500 GnRH cell bodies in the sheep brain are located in a region covering the anterior hypothalamus, the medial preoptic area, the diagonal band of Broca, and the septum. The axons of up to 50% of these cells terminate in the organum vasculosum of the lamina terminalis. The remainder terminate in the median eminence and form the final common pathway for the many factors that affect gonadotrophin secretion. Among the factors known to affect the frequency of the pulses (or the activity of the GnRH neurons) are nutrition, pheromones, photoperiod and gonadal steroids (negative and positive feedback). Factors that affect GnRH pulse amplitude are more difficult to determine because variations in pituitary responsiveness prevent the use of LH patterns as a 'bioassay'. Techniques developed recently have allowed the direct measurement of GnRH pulse amplitude and revealed inhibitory effects of oestradiol, but we do not know whether this effect is due to a reduction in the amount of GnRH released by each neurone or a reduction in the number of neurones releasing a pulse. It is unlikely that the factors that alter pulse frequency do so by directly affecting the GnRH cells. For example, it is obvious that other cells, with specific receptors for pheromonal or nutritional stimuli, formulate a signal that is transferred to the GnRH cells via interneurones. Similarly, it is likely that a hypothalamic clock intervenes between photoperiodic inputs and GnRH output. Opioidergic neurons have been proposed as a link in this system, but the complexity of their action makes it unlikely that they directly affect the GnRH neurons. The responses to steroids are simple and rapid, but steroid receptors have not been found in GnRH cells, so at least one other set of interneurones is involved.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1995

Prenatal development of somatosensory primary afferent connections in the sheep.

A summary is presented of recently published studies on the structural and functional development of cutaneous and muscle receptors and the connections of their afferent fibres in fetal sheep (n = 26) aged between 67 and 143 days gestation (term, 146 days). In these studies it was shown that primary afferent fibres projected to, and made synaptic connections with, dorsal horn neurons in lumbosacral spinal cord by 56-61 days gestation. Sensory innervation of the skin occurred later by about 75 days gestation and, at this age, stimulation of the skin first activated cutaneous afferent fibres and evoked a discharge in dorsal root ganglion and dorsal horn neurons. Muscle stretch first activated muscle spindles and evoked a discharge in dorsal root ganglion cells by about 75 days. Prior to this (by about 67 days) primary afferent fibres had begun to innervate motoneuron pools in the spinal cord, and motor nerves had begun to innervate muscle fibres. Both muscle spindle and cutaneous innervation were relatively simple at mid gestation indicating that the structure of sensory receptors need not be complex in order to generate a response. Neural pathways necessary for reflex activity involving muscle spindles are therefore present and functional by mid gestation as are cutaneous pathways projecting from the skin to the spinal cord.

Afferent Pathways↗

PubMed2004

Postzygotic isolating factor in sympatric speciation in Rhagoletis flies: reduced response of hybrids to parental host-fruit odors.

Rhagoletis pomonella is a model for sympatric speciation (divergence without geographic isolation) by means of host-plant shifts. Many Rhagoletis species are known to use fruit odor as a key olfactory cue to distinguish among their respective host plants. Because Rhagoletis rendezvous on or near the unabscised fruit of their hosts to mate, behavioral preferences for fruit odor translate directly into premating reproductive isolation among flies. Here, we report that reciprocal F(1) hybrids between the apple and hawthorn host races of R. pomonella, as well as between the host races and an undescribed sibling species infesting Cornus florida (flowering dogwood) do not respond to host fruit volatiles in wind-tunnel assays at doses that elicit maximal directed flight in parental flies. The reduced ability of hybrids to orient to fruit volatiles could result from a conflict between neural pathways for preference and avoidance behaviors, and it suggests that hybrids might suffer a fitness disadvantage for finding fruit in nature. Therefore, host-specific mating may play a dual role as an important postzygotic as well as a premating reproductive barrier to isolate sympatric Rhagoletis flies.

Animals↗

PubMed2005

Cortical, thalamic, and hypothalamic responses to cooling and warming the skin in awake humans: a positron-emission tomography study.

Thermoregulatory mechanisms are remarkably efficient, ensuring minimal temperature variation within the core of the human body under physiological conditions. Diverse afferent and efferent neural pathways contribute to the monitoring of core and skin temperature, generation of heat, and control of thermal exchange with the external environment. We have investigated the cortical, thalamic, and hypothalamic responses to cooling and warming by using positron-emission tomography activation imaging of subjects clad in a water-perfused suit, which enabled rapid change of their skin-surface temperature. Human brain regions that respond to changes in skin temperature have been identified in the somatosensory cortex, insula, anterior cingulate, thalamus, and hypothalamus, with evidence that the hypothalamic response codes for the direction of temperature change. We conclude that signals from thermosensors in the skin providing crucial afferent information to the brain are integrated with signals from central thermosensors, resulting in thermoregulatory responses that maintain core temperature within a remarkably narrow range.

Adult↗