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PubMed1998

Experience-dependent corticofugal adjustment of midbrain frequency map in bat auditory system.

Recent studies of corticofugal modulation of auditory information processing indicate that cortical neurons mediate both a highly focused positive feedback to subcortical neurons "matched" in tuning to a particular acoustic parameter and a widespread lateral inhibition to "unmatched" subcortical neurons. This cortical function for the adjustment and improvement of subcortical information processing is called egocentric selection. Egocentric selection enhances the neural representation of frequently occurring signals in the central auditory system. For our present studies performed with the big brown bat (Eptesicus fuscus), we hypothesized that egocentric selection adjusts the frequency map of the inferior colliculus (IC) according to auditory experience based on associative learning. To test this hypothesis, we delivered acoustic stimuli paired with electric leg stimulation to the bat, because such paired stimuli allowed the animal to learn that the acoustic stimulus was behaviorally important and to make behavioral and neural adjustments based on the acquired importance of the acoustic stimulus. We found that acoustic stimulation alone evokes a change in the frequency map of the IC; that this change in the IC becomes greater when the acoustic stimulation is made behaviorally relevant by pairing it with electrical stimulation; that the collicular change is mediated by the corticofugal system; and that the IC itself can sustain the change evoked by the corticofugal system for some time. Our data support the hypothesis.

Acoustic Stimulation↗

PubMed1997

Renal function after myocardial infarction and cardiac arrest in rats: role of ANP-induced albuminuria?

Renal function was measured by clearance technique before and after acute myocardial infarction (MI) induced by left coronary artery ligation in male Sprague-Dawley rats. The animals were anaesthetized with halothane-nitrous oxide, paralysed with pancuronium and artificially ventilated. All parameters were stable throughout the experiment in sham-operated time control animals (n = 8). After MI, rats developed left ventricular dysfunction with increased left ventricular end-diastolic pressure and decreased mean arterial pressure. MI produced antidiuresis and antinatriuresis without changes in glomerular filtration rate (GFR), lithium clearance or renal albumin excretion (n = 8). The antidiuretic and antinatriuretic responses to MI were similar in rats with chronic bilateral renal denervation (n = 5). Three additional rats with chronic bilateral renal denervation had cardiac arrest and were resuscitated with cardiac massage, i.v. lidocaine and intracardiac adrenaline administration. These animals showed a transient increase in urine flow rate, sodium and albumin excretion with maximum 30-60 min after resuscitation, while GFR and lithium clearance were normal. Since cardiac ischaemia and sympathetic stimulation are strong stimuli for the release of atrial natriuretic peptide (ANP), we examined if ANP (0.25, 0.50, and 1.00 microg kg(-1) min(-1), n = 8 per dose) affects urinary albumin excretion. ANP increased dose-dependently the urine/plasma concentration ratio of albumin relative to inulin, which suggests that ANP increases the glomerular permeability for albumin. We conclude that MI causes stimulation of renal tubular sodium and water reabsorption by a mechanism which is independent of intact renal innervation. MI does not produce any change in renal albumin excretion in rats, but transient albuminuria may be observed in rats following cardiac arrest and/or manoeuvres used in cardiac resuscitation. Since ANP produces albuminuria, we speculate that ANP may be an important mediator of albuminuria in states with elevated plasma concentrations of ANP.

Albuminuria↗

PubMed1990

Noxious somatic stimuli excite neurosecretory vasopressin cells via A1 cell group.

Activation of nociceptive somatic afferents excites hypothalamic neurosecretory cells and stimulates the release of vasopressin. To investigate the possibility that relevant afferent information is relayed through the A1 norepinephrine cell group of the caudal ventrolateral medulla, single-unit recording experiments were performed in pentobarbital sodium-anesthetized rats. The effects of somatic nerve stimulation, application of noxious somatic stimuli, and A1 region stimulation on the activity of putative vasopressin-secreting neurosecretory cells of the supraoptic nucleus were compared. The predominant effect of femoral and sciatic nerve stimulation on these cells was excitation, 54% (n tested = 113) displaying a marked increase in discharge probability, which had a mean onset latency of 72 +/- 3 ms and a mean duration of 114 +/- 9 ms. Almost all cells (96%) responding to somatic nerve stimulation were also excited by pinching of the ipsilateral or contralateral hindlimb paw, and the majority (84%) displayed a matching but shorter latency response to A1 region stimulation (mean onset 35 +/- 4 ms, duration 55 +/- 9 ms). A1 region injections of the inhibitory neurotransmitter gamma-aminobutyric acid reversibly blocked the effects of both somatic nerve stimulation (n = 14) and paw pinch (n = 9) on putative vasopressin cells. These results indicate that excitation of vasopressinergic neurosecretory cells by noxious somatic stimuli requires activation of neurons of the caudal ventrolateral medulla and hence are consistent with the proposal of a role for the A1 norepinephrine cell group.

Animals↗

PubMed1994

Role of protein phosphorylation in the degranulation of electropermeabilized human neutrophils.

We have studied the role of protein phosphorylation in the degranulation response of human neutrophils by measuring the effect of ATP depletion and the addition of the protein kinase inhibitor staurosporine in electropermeabilized human neutrophils, activated with Ca2+ and/or GTP-gamma-S. Our studies were carried out in the presence of cytochalasin B to prevent inhibitory effects of actin polymerization on the degranulation response. It was found that protein phosphorylation plays an important role in the degranulation response in cells stimulated with the single stimuli Ca2+ or GTP-gamma-S. However, in neutrophils stimulated with the combination of these activators degranulation can occur without the apparent need for protein phosphorylation, albeit with a slower rate than with protein phosphorylation.

Adenosine Triphosphate↗

PubMed1990

Convergence of Ia fibres from synergistic and antagonistic muscles onto interneurones inhibitory to soleus in humans.

1. The possibility that Ia afferent fibres from the gastrocnemius medialis (GM) and from the tibialis anterior (TA) muscle could converge on to a single interneuronal pool inhibitory to the soleus motoneurones was investigated. 2. The soleus H reflex, evoked by tibial nerve stimulation in the popliteal fossa, was conditioned by separate or combined stimulation of the nerves to the GM or TA muscles. Stimulus intensity was below the motor threshold (MTh), and the conditioning-test intervals were such as to evoke short-latency inhibition of the soleus H reflex. Care was taken to avoid current spread and artifacts connected with the closeness in time and space of the conditioning and test stimuli. 3. Separate stimulation of both GM and TA nerves was able to induce significant inhibitory effects on the H reflex amplitude at stimulus strengths larger than 0.75 x MTh, on the average. Combined stimulation of the two nerves was able to reduce the H reflex at lower stimulus strengths, at which either nerve was ineffective alone. 4. Conditioning stimulus strengths close to the MTh reduced the H reflex to approximately 80% of the control value, both on single and combined stimulation, i.e. saturation of the inhibitory effect was found. 5. By extrapolating the regression line through the normalized data from all subjects, it was assumed that the smallest stimulus strength necessary to drive the inhibitory interneurones to threshold was, on the average, 0.5 and 0.6 x MTh, on combined and separate nerve stimulation, respectively. 6. Tonic voluntary activation of the soleus abolished the inhibitory effects of both separate and combined stimulations. This was tested on the H reflex, on the rectified and averaged EMG, and on the peristimulus histogram of single motor unit discharge. 7. The findings strongly suggest the existence of spatial summation of the effects from GM and TA muscle at the level of a single interneuronal pool. Most probably, the responsible afferent fibres are group I spindle afferents, and the interneurones those mediating the reciprocal inhibition. The data do not support the notion of parallel pathways, exclusive to each nerve.

Adult↗

PubMed1987

Action of centrally mediated autonomic stimulation on human upper gastrointestinal transit: a comparative study of two stimuli.

Two well established experimental stressors, hand immersion in cold water, and mental stimulation with dichotomous listening, were applied to 37 normal subjects after the ingestion of a standard meal. Orocaecal transit was measured by serial exhaled breath hydrogen sampling. Cold water significantly delayed transit compared with warm water control (warm water 71.8 +/- 3.6 mins v cold water 93.2 +/- 5.7 mins p less than 0.01), with significant rises in blood pressure pulse rate perceived discomfort and plasma catecholamines. In contrast mental stimulation was unaccompanied by any change in transit (control; 67.4 +/- 4.7 v test 64.3 +/- 5.3 mins p greater than 0.1) despite a significant rise in pulse rate, skin conductance and plasma catecholamines. Repeated cold water immersion studies in eight individuals produced consistent orocaecal transit and autonomic responses, whereas mental stimulation showed reduced autonomic responses on repeat testing, suggesting that tolerance to the stimulus had occurred. The results of these studies show stimulus specific gastrointestinal response patterns to autonomic stimuli, and appear to have important implications for the design of future studies of human gastrointestinal autonomic physiology and for the investigation of patients with stress related gut dysfunction.

Acoustic Stimulation↗

PubMed1995

Behavioral responses to uterine or vaginal distension in the rat.

Afferent fibers in the rat hypogastric and pelvic nerves supply the uterus and vagina, respectively, the former being responsive mainly to intense uterine stimuli, the latter to gentle and intense vaginal stimuli (Berkley et al. 1993c). If such responses result in sensory experiences, those produced by uterine and vaginal stimulation should differ, uterine stimuli being experienced mainly as pain and vaginal stimuli experienced in various ways, including pain. To test this hypothesis, 48 young virgin rats were first trained to make an operant response to escape a noxious tail-pinch stimulus. Latex balloons inserted into the rat's uterine horn or vagina were then distended to various volumes and the metestrous rat's detection behaviors and operant escape response probabilities measured. Approximately 26% of the 23 rats tested failed to respond to uterine stimulation, even when it produced ischemia. For the rest, detection and escape responses occurred only to ischemic stimuli and never to all of them, even at the highest volumes. In contrast, all 25 rats tested responded readily to vaginal distension, often to all of them at high volumes. Detection behaviors occurred at distension magnitudes lower than those that evoked escape responses. These results support the hypothesis that sensory consequences of uterine and vaginal stimulation differ. Because effective uterine stimuli were larger than any that would occur in a normal physiological state in non-pregnant/parturient rats, normally occurring uterine states in such rats are probably insensible. In addition, while the behavioral responses did indeed reflect differences in hypogastric and pelvic nerve response properties, the results also indicated that activity produced in those fibers, even by abnormal stimuli, does not inevitably result in behavior.

Animals↗

PubMed1991

Halothane alters control of intracellular Ca2+ mobilization in single rat ventricular myocytes.

In an attempt to understand the cellular mechanisms underlying volatile anesthetic-induced myocardial depression, halothane-induced negative inotropy was investigated in an animal model through continuous monitoring of intracellular Ca2+ concentration [( Ca2+]i) in rat ventricular myocytes loaded with fura-2. Single cells were stimulated with 15 mM caffeine or 15 mM extracellular K+ (K+O) or were paced by extracellular glass suction pipette electrode. With each stimulus modality, halothane (0.6-1.5%) caused a significant (P less than 0.05) and dose-dependent depression of the Ca2+ transient. Caffeine and electrically stimulated Ca2+ transients were reduced, in 1.5% halothane, to 35 +/- 14 and 42 +/- 8% of control, respectively. Resting or basal [Ca2+]i was unaffected by halothane. Halothane did not elicit spontaneous Ca2+ transients in these cells. Single cells stimulated by trains of electrical stimuli at 1.0, 1.5, and 2.0 Hz showed a change in [Ca2+]i from prestimulus levels to a stimulated baseline steady state that appeared to increase with stimulus frequency. Halothane at 0.7% increased the change in resting to stimulated baseline [Ca2+]i and depressed net transients (P less than 0.05) at 1.0 and 1.5 Hz. In contrast, 0.1 microM ryanodine depressed the Ca2+ transients in myocytes stimulated by trains of stimuli, but did not potentiate the change in stimulated baseline [Ca2+]i at any pacing rate. The results are consistent with the hypothesis that halothane reduces Ca2+i availability by causing a net loss of Ca2+ from the sarcoplasmic reticulum. The results from experiments using onset of pacing to induce a sudden increase in Ca2+i load in previously quiescent myocytes suggest that halothane may act to limit sarcoplasmic reticulum and/or sarcolemmal uptake/extrusion mechanisms, as compared to ryanodine, which depletes sarcoplasmic reticulum Ca2+ stores without affecting reuptake and extrusion.

Animals↗

PubMed2003

The effects of acute and chronic lipopolysaccharide infusion in rats on the efferent function of sensory nerves in the isolated mesenteric arterial bed.

Capsaicin-sensitive sensory neurons are stimulated by noxious stimuli, and may be activated in endotoxaemia. The present study investigated the acute and chronic effects of lipopolysaccharide upon the efferent function of these nerves. Conscious rats received infusion (i.v.) of lipopolysaccharide (150 microg kg(-1) h(-1)) or saline for 2 or 24 h. Following infusion, animals were killed and the mesenteric arterial bed isolated and perfused with Krebs' solution. Electrical field stimulation of capsaicin-sensitive sensory nerves was investigated. Postjunctional mechanisms of sensory neurotransmission were examined using calcitonin gene-related peptide, and endothelial and smooth muscle function assessed using acetylcholine and sodium nitroprusside, respectively. All preparations exhibited dose dependency to the agonists, and frequency dependency to electrical field stimulation. No significant differences were observed between the four groups (2-h saline, 24-h saline, 2-h lipopolysaccharide and 24-h lipopolysaccharide) with regard to responses to electrical field stimulation, acetylcholine, sodium nitroprusside or calcitonin gene-related peptide. Thus, the efferent function of capsaicin-sensitive sensory nerves is unaltered in the isolated mesenteric arterial bed prepared ex vivo from rats receiving lipopolysaccharide, either acutely (2 h) or chronically (24 h).

Animals↗

PubMed1994

Priming for the synthesis of 5-lipoxygenase products in human blood ex vivo by human granulocyte-macrophage colony-stimulating factor and tumor necrosis factor-alpha.

BACKGROUND: Previous studies reported the priming effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor-alpha (TNF alpha) on leukotriene synthesis by isolated polymorphonuclear leukocytes; however, little is known as of yet of these biologic effects of the two cytokines in a physiologic environment. EXPERIMENTAL DESIGN: In this study, we investigate the effects of GM-CSF and TNF alpha on the synthesis of 5-lipoxygenase (5-LO) products in heparinized blood stimulated ex vivo, using reverse phase high performance liquid chromatography analysis of deproteinized plasma samples. RESULTS: Stimulation of blood with f-Met-Leu-Phe resulted in the accumulation of up to 30 pmol of 5-LO products/ml of plasma. Preincubation of blood with 100 pM GM-CSF or 1.2 nM (200 units/ml) TNF alpha for 30 minutes at 37 degrees C before stimulation with f-Met-Leu-Phe resulted in a marked enhancement (> 5-fold) of the synthesis of leukotriene B4 and 5(S)-hydroxyeicosatetraenoic acid, which were formed in equivalent amounts. GM-CSF and TNF alpha priming activities were detectable at concentrations as low as 3 pM and 6 pM (1 unit/ml), respectively. The preincubation times required for optimal priming by GM-CSF and TNF alpha were different (40 and 10 minutes, respectively), and the effects of the two cytokines on leukotriene B4 and 5(S)-hydroxyeicosatetraenoic acid synthesis were additive, suggesting different priming mechanisms. The synthesis of 5-LO products in primed blood was also induced by platelet-activating factor, the complement fragment C5a, the particulate stimulus zymosan, and the ionophore A23187, but not by interleukin-8. Polymorphonuclear leukocytes and mononuclear cells accounted for 80% and 20% of the synthesis of 5-LO products, respectively. CONCLUSIONS: These data demonstrate that GM-CSF and TNF alpha exert very potent priming effects on the biosynthesis of 5-LO products in whole blood stimulated by various stimuli and strongly support that these cytokines could be important modulators of lipid mediator synthesis in physiologic and pathophysiologic conditions.

Arachidonate 5-Lipoxygenase↗

PubMed2006

Impairments of hippocampal synaptic plasticity induced by aggregated beta-amyloid (25-35) are dependent on stimulation-protocol and genetic background.

The aggregation of beta-amyloid to plaques in the brain is one of the hallmarks of Alzheimer disease (AD). Numerous studies have tried to elucidate to what degree amyloid peptides play a role in the neurodegenerative developments seen in AD. While most studies report an effect of amyloid on neural activity and cognitive abilities of rodents, there have been many inconsistencies in the results. This study investigated to what degree the different genetic backgrounds affect the outcome of beta-amyloid fragment (25-35) on synaptic plasticity in vivo in the rat hippocampus. Two strains, Wistar and Lister hooded rats, were tested. In addition, the effects of a strong (600 stimuli) and a weak stimulation protocol (100 stimuli) on impairments of LTP were analysed. Furthermore, since the state of amyloid aggregation appears to play a role in the induction of toxic processes, it was tested by dual polarisation interferometry to what degree and at what speed beta-amyloid (25-35) can aggregate in vitro. It was found that 100 nmol beta-amyloid (25-35) injected icv did impair LTP in Wistar rats when using the weak but not the strong stimulation protocol (P < 0.001). One-hundred nano mole of the reverse sequence amyloid (35-25) had no effect. LTP in Lister Hooded rats was not impaired by amyloid at any stimulation protocol. The aggregation studies showed that amyloid (25-35) aggregated within hours, while amyloid (35-25) did not. These results show that the genetic background and the stimulation protocol are important variables that greatly influence the experimental outcome. The fact that amyloid (25-35) aggregated quickly and showed neurophysiological effects, while amyloid (35-25) did not aggregate and did not show any effects indicates that the state of aggregation plays an important role in the physiological effects.

Alzheimer Disease↗

PubMed2005

Balance of monosynaptic excitatory and disynaptic inhibitory responses of the globus pallidus induced after stimulation of the subthalamic nucleus in the monkey.

The subthalamic nucleus (STN) plays a pivotal role in controlling the activity of both the external and internal segments of the globus pallidus (GPe and GPi, respectively). Both nuclei receive monosynaptic excitatory and disynaptic GPe-mediated inhibitory inputs from the STN. Thus, we investigated the balance of these antagonistic inputs that may determine the overall response of pallidum to STN activation in monkeys. Single stimulation of the STN evoked a short-latency excitation followed by a weak inhibition in GPe neurons and a short-latency, very short-duration excitation followed by a strong inhibition in GPi neurons. Burst high-frequency stimulation (BHFS) (10 stimuli with 100 Hz) of the STN (STN-BHFS) evoked powerful excitatory responses in GPe neurons. Local injection of a mixture of 1, 2, 3, 4-tetrahydro-6-nitro-2, 3-dioxobenzo[f]quinoxaline-7-sulfonamide (NBQX; AMPA/kainate receptor blocker) and 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP; NMDA receptor blocker) greatly diminished or abolished excitatory responses to the STN stimulation. In contrast to the GPe, STN-BHFS evoked a predominantly inhibitory response in GPi neurons. The inhibition could be blocked either by a local application of the GABAA receptor antagonist gabazine or by an injection of an NBQX/CPP/gabazine mixture into the GPe. STN-BHFS induced weak excitatory or inhibitory responses in a small number of phasically active putamen neurons. These data suggest that with single stimulation and during STN-BHFS, the STN-GPe excitatory response dominates over the STN-GPe-GPe recurrent inhibition in the GPe, whereas the STN-GPe-GPi inhibitory response dominates over the STN-GPi excitatory response in the GPi.

Animals↗

PubMed1969

Effects of secretin, pancreozymin, or gastrin on the response of the endocrine pancreas to administration of glucose or arginine in man.

Intravenous administration of porcine secretin or pancreozymin or synthetic human gastrin II resulted in raised increments in serum immunoreactive insulin during intravenous infusion of glucose in normal man. Enhancement of serum immunoreactive insulin by each hormone was associated with accelerated disposal of glucose. In response to prolonged intravenous infusion of arginine with pancreozymin there was a maintained rise in immunoreactive insulin and glucagon-like immunoreactivity in the blood. These effects of pancreozymin and arginine were not reproduced with secretin and arginine, and may have been due to the stimulation of glucagon secretion together with insulin by pancreozymin. Enteric infusion of hydrochloric acid, or stimulation of gastric acid secretion by betazole, presumed to cause release of endogenous secretin, led to enhancement of insulin secretion during intravenous infusion of glucose. Enteric infusion of arginine, presumed to cause release of endogenous pancreozymin, led to a rise in serum immunoreactive insulin not attributable to effects of circulating glucose and amino acids. It is concluded that secretin and pancreozymin released in response to physiological stimuli contribute to stimulation of the endocrine pancreas after ingestion of food.

Adolescent↗

PubMed1984

[Physical dimensions influence the functional property of the semicircular canal].

The functional dependence of the semicircular canal upon its physical dimensions was evaluated by measuring the internal radius (r), the radius of curvature (R) and the cupula radius (rC) of the posterior canal in 10 freshly dissected frog labyrinths. These values have been compared to the same parameters of the cat labyrinth. The coefficients I, B, K in the Steinhausen equation were determined for both animals. The A ratio between cupula deflection and endolymph displacement was also calculated by utilizing the Bernard equation. The A ratio is three times larger in the frog than in the cat. It follows that if the same acceleration produces similar endolymph displacements in the posterior canal of both animals, the cupula deflection will be larger in the frog. The solution of the Steinhausen equation in the presence of a constant acceleration, however, reveals that the same stimulus intensity will result in a larger endolymph displacement in the cat posterior canal; similarly, the endolymph displacement directly depends on the duration of the stimulating period in both animals. Contrary to the Bernard assumption, these effects generate a G ratio (psi frog/psi cat) which is less than the Q ratio (A frog/A cat). Moreover, G decreases on increasing the duration of the stimulating period. For stimuli of short duration the semicircular canal of a small animal is expected to exhibit a higher sensitivity than that of a larger one. However, the definitive primary afferent discharge will be largely controlled by the receptor/generator potential properties.

Acoustic Stimulation↗

PubMed2003

Sphingosine 1-phosphate is a novel inhibitor of T-cell proliferation.

Sphingosine 1-phosphate (S1P) is a pleiotropic lysosphingophospholipid stored and secreted by platelets. Using reverse transcription-polymerase chain reaction and flow cytometric analyses, we determined the expression of S1P receptors (S1P1, S1P3, S1P4, and S1P5) in peripheral blood T cells. T cells were induced to proliferate in the presence of phorbol 12-myristate 13-acetate (PMA) plus ionomycin, anti-CD3 plus anti-CD28, and allogeneic immature or mature dendritic cells. This activity was inhibited by the addition of S1P. Enhanced T-cell proliferation was observed when these cells were stimulated with the same stimuli, but were incubated in serum-free media (SFM). Addition of S1P to SFM inhibited the stimulation of T cells induced by T-cell stimuli, suggesting that S1P is an important inhibitory molecule present in the serum. T-cell proliferation was also inhibited by the addition of dihydrosphingosine 1-phosphate (DHS1P), sphingosine, and ceramide; however, the latter 2 sphingolipids required higher concentrations than S1P. Pretreatment of T cells with pertussis toxin (PTX) blocked the inhibitory effect of S1P on activation with PMA plus ionomycin, but not on activation with anti-CD3 plus anti-CD28. This is corroborated with the down-regulation of S1P1 in T cells stimulated with anti-CD3 plus anti-CD28. Similarly, PTX did not affect the inhibitory effect of S1P on T-cell proliferation when dendritic cells were used as stimuli. Further, S1P or DHS1P but not ceramide or sphingosine enhanced rather than decreased secretion of interleukin 2 and interferon gamma by T cells stimulated with anti-CD3 plus anti-CD28. These results show differential effects of S1P on polyclonal T-cell proliferation and cytokine secretion.

Antibodies↗

PubMed1975

[Long-lasting changes of irritability in the somatosensory cortex of rabbits following tetanic stimulation of the tooth pulp].

Tetanic stimulation of the tooth pulp produced long lasting increases in potentials released by stimulation of the tooth pulp with single stimuli in the sensomotor cortex of rabbits. Stimulation with 200 impulses/sec for 5 sec produced changes of irritability that are demonstrable for 10-50 min depending on the intensity of stimulation. The lower rate limit for producing such changes is 25 impulses/sec. At a rate of 200 impulses/sec, a stimulation time of 25 msec was necessary to produce these changes. The postexcitatory depression occuring after single stimuli within 10-40 msec was increased by tetanic stimulation, whereas facilitation observed 5 msec after single stimuli was unaffected.

Action Potentials↗

PubMed1996

Middle and long latency somatosensory evoked potentials after painful laser stimulation in patients with fibromyalgia syndrome.

Ten female patients with fibromyalgia syndrome (FS) were investigated with laser evoked potentials (LEPs) after hand stimulations and compared with 10 female pain-free and age-matched control patients. FS patients exhibited significantly lower heat pain thresholds than controls (P < 0.05) and had higher amplitudes of LEP components N170 (P < 0.01) and P390 (P < 0.05) in response to intensities of 20 W (beam diameter 5 mm, duration 20 msec, wavelength 10.6 microns). N170 additionally appeared with a broader distribution over bilateral central, vertex and fronto-central leads which contrasted to the control group and studies in healthy subjects where N170 was much more restricted to central and midtemporal positions contralateral to the stimulated hand. Auditory stimuli interspersed between laser impulses that served to announce subjects to rate the perceived pain elicited auditory evoked potentials that were not different between groups indicating no differences of general vigilance level to account for observed LEP effects. P390 amplitude enhancement might indicate greater attention and cognitive processing of nociceptive stimuli in FS subjects. Effects upon N170 rather point to exogenous factors like peripheral and spinal sensitization or reduced cortical or subcortical inhibition of nociception.

Adult↗

PubMed1980

[Effect of hypothalamic stimulation on the appearance of the early and delayed responses of the somato-sympathetic reflex].

Stimulation of somatic nerves evoked in the cat L2--L3 white rami a late two--wave response. High frequency stimulation of the hypothalamus induced an increase of the blood pressure, facilitation of the first component and suppression of the second component of the late response. The components of the early response were insignificantly affected by the stimulation. The paired stimuli technique revealed interaction of descending and peripheral afferent excitation of sympathetic preganglionic neurons. The role of baroreceptor and hypothalamic excitation in spinal sympathetic mechanisms is discussed.

Animals↗