Single units activities in ventral posterior and posterior group thalamic nuclei during nociceptive and non nociceptive stimulations in the cat.

The purpose of this study was to define, in hyperventilated and unanesthetized cats, the role of the posterior thalamic nuclei in pain mechanisms. Unit activities of these structures were compared to those of the ventro-posterior nucleus during non-noxious (touch, brushing) and noxious stimulations (pinches and intra-arterial injections of bradykinin into the limbs). 135 cells with somatic inputs and clear peripheral excitatory receptive field were studied. The cells driven by noxious stimulations were located in the posterior group nuclei as anatomically defined by Rinvik. These units, preferentially excited from contralateral receptive fields, were localized in POm, POl, suprageniculate nuclei, the magnocellular division of the medial geniculate body (Mgmc) and the ventral part of the lateral posterior nucleus. At this level two groups of units were found: those driven only by noxious stimulations and those driven by both noxious and non-noxious stimulations. On contrast, cells recorded at the levels of the VPm and VPl were not activated by noxious stimuli. These results emphasize the role of the posterior thalamic nuclei in pain processing.     

异丙酚对正常大鼠脊髓背角感觉神经元反应性的抑制作用

脊髓背角感觉神经元不仅在感觉信息的传递和调节中起到重要作用,也是各种内源性和外源性药物的作用靶位.为了解静脉麻醉剂异丙酚是否对背角感觉神经元的反应性具有调节作用,本实验采用在体单细胞胞外记录技术,观察了脊髓背表面直接滴注0.5 μmol异丙酚对戊巴比妥钠麻醉大鼠脊髓背角广动力域(WDR)神经元和低阈值机械感受型(LTM)神经元反应性的影响.实验发现,异丙酚能抑制背角WDR神经元由施加于外周感受野伤害性热刺激(45、47、49和53℃,15 s)和夹捏机械刺激(10 s)诱发的反应性,与DMSO对照组比较具有显著性统计学差异(P＜0.05);同样,异丙酚对非伤害性机械刺激诱发的WDR或LTM神经元的反应性也具有显著的抑制作用(P＜0.05).本结果提示,异丙酚可直接作用于正常大鼠脊髓背角神经元,对由非伤害性和伤害性纤维介导的神经元反应性均产生抑制作用,因此异丙酚的脊髓抗伤害作用可能不是特异性的.     

Vascular effects of substance P change synaptic responsiveness of cat dorsal horn neurons

The effects of systemically administered substance P were examined on the responses induced by noxious (radiant heat) and non-noxious (air jets) peripheral stimuli in dorsal horn neurons of the feline spinal cord. Substance P produced a significant fall in arterial blood pressure and selectively enhanced responses to noxious heat stimulation. Other vasoactive substances administered systemically caused either selective increases or decreases in noxious heat induced responses which coincided with decreases or increases in systemic arterial blood pressure respectively. It was concluded that the selective neuronal effects of substance P were secondary to changes in vascular perfusion in the area stimulated by the radiant heat source.     

Period responses to Zeitgeber signals stabilize circadian clocks during entrainment

Circadian clocks with characteristic period (τ) can be entrained to light/dark (LD) cycles by means of (i) phase shifts which are due to D/L “dawn” and/or L/D “dusk” transitions, (ii) period changes associated with long-term light exposure, or (iii) by combinations of the above possibilities. Based on stability analysis of a model circadian clock it was predicted that nocturnal burrowing mammals would benefit less from period responses than their diurnal counterparts. The model further predicted that maximal stability of circadian clock is reached when the clock slightly changes both its phase and period in response to light stimuli. Analyses of empirical phase response curve (PRC) and period response curve (τRC) of some diurnal and nocturnal mammals revealed that PRCs of both diurnal and nocturnal mammals have similar waveform while τRCs of nocturnal mammals are of smaller amplitude than those of diurnal mammals. The shape of the τRC also changes with age and with increasing strength of light stimuli. During erratic fluctuations in light intensity under different weather conditions, the stability of phase of entrainment of circadian clocks appears to be achieved by an interplay between phase and period responses and the strength of light stimuli.     

In vivo and in vitro patch-clamp recording analysis of the process of sensory transmission in the spinal cord and sensory cortex

Following the integration and modification of the sensory inputs in the spinal cord, the information is transmitted to the primary sensory cortex where the integrated information is further processed and perceived. Processing of the sensory information in the spinal cord has been intensively investigated. However, the mechanisms of how the inputs are processed in the cortex are still unclear. To know the correlation of the sensory processing in the dorsal horn and cortex, in vivo and in vitro patch-clamp recordings were made from rat dorsal horn and sensory cortex. Although dorsal horn neurons showed spontaneous and evoked EPSCs by noxious and non-noxious stimuli, most somatosensory neurons located at 100 to 1000 microm from the surface of the cortex exhibited an oscillatory activity and received synaptic inputs from non-noxious but not noxious receptors. These observations suggest that the synaptic responses in cortical neurons are processed in a more complex manner; and this may be due to the reciprocal synaptic connection between thalamus and cortex.     

Pedal serotonergic neurons modulate the synaptic input of withdrawal interneurons ofHelix

A group of serotonergic cells, located in the pedal ganglia ofHelix lucorum, modulates synaptic responses of neurons involved in withdrawal behavior. Extracellular or intracellular stimulation of these serotonergic cells leads to facilitation of spike responses to noxious stimuli in the putative command neurons for withdrawal behavior. Noxious tactile stimuli elicit an increase in background spiking frequency in the modulatory neurons and a corresponding increase in stimulus-evoked spike responses in withdrawal interneurons. The serotonergic neurons have processes in the neuropil of the parieto-visceral ganglia complex, consistent with their putative role in modulating the activity of giant parietal interneurons, which send processes to the same neuropil and to the pedal ganglia. The serotonergic cells respond to noxious tactile and chemical stimuli. Although the group as a whole respond to noxious stimuli applied to any part of the body, most cells respond more to ipsilateral than contralateral stimulation, and exhibit differences in receptive areas. Intracellular investigation revealed electrical coupling between serotonergic neurons which could underlie the recruitment of members of the group not responding to a given noxious stimulus.     

Depression and facilitation of synaptic responses in cat dorsal horn by substance P administered into substantia gelatinosa

The effects of substance P and an enkephalin analogue administered by electrophoresis into the substantia gelatinosa have been examined on the synaptic responses of dorsal horn neurons evoked by peripheral stimulation. Extracellular neuronal firing was studied in cats under pentobarbitone anesthesia. The enkephalin produced naloxone-reversible depression of responses to noxious heat stimulation without affecting responses to non-noxious stimuli. Substance P caused a selective enhancement or depression of noxious responses. It was tentatively concluded that substance P may modify the release of a sensory transmitter and produce direct post synaptic changes in membrane excitability.     

Responses of neurons of the solitary tract nucleus to noxious colorectal distension in rats

In experiments on anaesthetized rats, the neuronal mechanisms underlying processing of the nociceptive information from the colon within the nucleus of the solitary tract were studied. In addition, the role of nitric oxide in these processes was estimated. Analysis of changes in c-fos expression revealed that nociceptive colorectal distension (CRD) resulted in activation of neurons mainly in the medial, commissural, parvicellular and dorsomedial subnuclei of the solitary tract nucleus. Non-noxious CRD evoked in these subdivisions weak phasic excitatory neuronal responses. Under noxious CRD, neurons with phasic (58%) and tonic (42%) responses were revealed. The phasic neuron responses were significantly enhanced in comparison with non-noxious CRD. Inhibition of the neuronal NO-syntheses resulted in significant decrease of neuron responses to noxious CRD and the number of cells with tonic reactions. Therefore, neurons with tonic responses may be directly related to NO-depended processing ofnociceptive information from colon.     

Aromatase immunoreactivity in the rat brain: Gonadectomy-sensitive hypothalamic neurons and an unresponsive “limbic ring” of the lateral septum-bed nucleus-amygdala complex

The aromatase (estrogen synthetase) enzyme catalyzes the conversion of androgens to estrogens in peripheral tissues, as well as in the brain. Our study aimed at comparing the brain distribution of aromatase-immunoreactive neurons in male and female, normal and gonadectomized rats. Light microscopic immunostaining was employed using a purified polyclonal antiserum raised against human placental aromatase. Two anatomically separate aromatase-immunoreactive neuronal systems were detected in the rat brain: A “limbic telencephalic” aromatase system was composed by a large population of labeled neurons in the lateral septal area, and by a continuous “ring” of neurons of the laterodorsal division of the bed nucleus of stria terminalis, central amygdaloid nucleus, stria terminalis, and the substantia inominata-ventral pallidum-fundus striati region. The other, “hypothalamic” aromatase system consisted of neurons scattered in a dorsolateral hypothalamic area including the paraventricular, lateral and dorsomedial hypothalamic nuclei, the subincertal nucleus as well as the zona incerta. In addition, a few axon-like processes (unresponsive to gonadectomy) were present in the preoptic-anterior hypothalamic complex, the ventral striatum, and midline thalamic regions. No sexual dimorphism was observed in the distribution or intensity of aromatase-immunostaining. However, 3 days, 2, 3, 8, 16, or 32 weeks after gonadectomy, aromatase-immunoreactive neurons disappeared from the hypothalamus, whereas they were still present in the limbic areas of both sexes. The results indicate the existence of two distinct estrogen-producing neuron systems in the rat brain: (1) a “limbic ring” of aromatase-labeled neurons of the lateral septum-bed nucleus-amygdala complex unresponsive to gonadectomy; and (2) a sex hormone-sensitive “hypothalamic” aromatase neuron system.     

Receptive fields of second-order neurons in the olfactory bulb of the hamster

Electrical stimulation of nerve fibers emerging from different positions of the olfactory epithelium was used to determine the receptive fields for 52 olfactory bulb neurons in the hamster. The responses of olfactory bulb neurons were recorded extracellularly with metal-filled micropipettes. Suprathreshold stimuli (500 microA) were applied to each of eight standard epithelial positions spaced approximately 250 microns apart, and the position, or positions, which, when stimulated, produced a response in the bulb were taken as an index of the neuron's receptive field. The results indicate that most bulb neurons have very localized receptive fields limited to only one or two stimulating positions. Furthermore, there was a statistically significant correlation between the location of a neuron's receptive field in the olfactory epithelium and the recording depth of the neuron in the olfactory bulb (Spearman rank correlation coefficient, rs, 0.67, P < 0.001). These findings demonstrate that in the mammalian olfactory system there exists a topographical projection of input from localized regions in the epithelium onto the second-order neurons in the olfactory bulb.     

Responses of spinohypothalamic tract neurons in the thoracic spinal cord of rats to somatic stimuli and to graded distention of the bile duct

Anatomical studies indicate that a relatively large percentage of spinohypothalamic tract (SHT) neurons are located within thoracic spinal segments. The aim of this study was to characterize the responses of SHT neurons in these segments of rats to innocuous and noxious stimulation of the skin and of a visceral structure, the bile duct. In addition, we attempted to determine the trajectories of the axons of the examined neurons within the diencephalon and brainstem. Fifty-three SHT neurons were recorded within segments T8-T13 in urethane anesthetized rats. Each cell was antidromically activated using current pulses < or = 30 microA delivered from the tip of an electrode located within the contralateral hypothalamus. The recording points were located in the superficial dorsal horn (9) and deep dorsal horn (44). All examined SHT neurons had receptive fields on the posterior thorax and anterior and ventral abdomen of the ipsilateral side. Ninety percent of the 41 SHT neurons responded exclusively (13) or preferentially (24) to noxious cutaneous stimuli. Thirteen of 27 (48%) examined units were activated by forceful distention of the bile duct. Response thresholds ranged from 30 to 40 mmHg. Responses incremented as pressures were increased to 50-80 mmHg. The axons of 22 of 28 (79%) examined SHT neurons appeared to cross the midline within the hypothalamus and terminate in the ipsilateral hypothalamus, thalamus or midbrain. The results indicate that SHT neurons in thoracic spinal cord of rats are capable of conveying somatic and visceral nociceptive information from the bile duct directly to targets at various levels of the brain bilaterally.     

刺激杏仁基底外侧核对外侧缰核神经元单位放电的影响

用玻璃微电极细胞外记录大鼠外侧缰核(LHN)神经元的单位放电。共记录了110个神经元。其中痛兴奋神经元(LHPE)75个;痛抑制神经元(LHPI)11个;广动力型神经元2个;无反应神经元17个;此外还有5个对躯体与内脏伤害性刺激反应不同的神经元。电刺激杏仁基底外侧核(以下简称杏仁核,AMG)对LHPE和LHPI的自发放电主要产生抑制作用,分别占总数的81.1％和72.7％,并抑制其对伤害性刺激的反应;对无反应神经元和广动力型神经元无明显影响。AMG内微量注射吗啡能抑制LHPE的伤害性刺激反应,但对其自发放电无明显影响。微量注射纳洛酮则可增加LHPE的自发放电频率,并加强其对伤害性刺激的反应。注射纳洛酮还可以取消电针对LHPE的伤害性刺激反应的抑制作用。     

Ultrastructural Analysis of the Terminals of Various Somatosensory Pathways in the Ventrobasal Complex of the Raft Thalamus: An Electron-Microscopic Study Using Wheatgerm Agglutinin Conjugated to Horseradish Peroxidase as an Axonal Tracer

We used wheatgerm agglutinin conjugated to horseradish peroxidase (WGA:HRP) as an anterograde tracer to label the terminals of the lemniscal, spinothalamic, and trigeminothalamic pathways in the ventrobasal complex of the rat thalamus (VB). The use of benzidine dihydrochloride (BDHC) as the chromogen allowed us to view the labeled profiles with the electron microscope and permitted us to compare the morphology of the terminals from the various pathways. We found that all the labeled somatosensory pathways terminate in the VB in the form of large terminals that contain round synaptic vesicles and make numerous asymmetrical synaptic contacts, usually with dendritic protrusions and proximal dendrites. The present results demonstrate that pathways conveying noxious and non-noxious somatosensory information terminate upon thalamic neurons with synaptic terminals having similar morphological features.     

Involvement of ERK Phosphorylation of Trigeminal Spinal Subnucleus Caudalis Neurons in Thermal Hypersensitivity in Rats with Infraorbital Nerve Injury

To evaluate the involvement of the mitogen-activated protein kinase (MAPK) cascade in orofacial neuropathic pain mechanisms, this study assessed nocifensive behavior evoked by mechanical or thermal stimulation of the whisker pad skin, phosphorylation of extracellular signal-regulated kinase (ERK) in trigeminal spinal subnucleus caudalis (Vc) neurons, and Vc neuronal responses to mechanical or thermal stimulation of the whisker pad skin in rats with the chronic constriction nerve injury of the infraorbital nerve (ION-CCI). The mechanical and thermal nocifensive behavior was significantly enhanced on the side ipsilateral to the ION-CCI compared to the contralateral whisker pad or sham rats. ION-CCI rats had an increased number of phosphorylated ERK immunoreactive (pERK-IR) cells which also manifested NeuN-IR but not GFAP-IR and Iba1-IR, and were significantly more in ION-CCI rats compared with sham rats following noxious but not non-noxious mechanical stimulation. After intrathecal administration of the MEK1 inhibitor PD98059 in ION-CCI rats, the number of pERK-IR cells after noxious stimulation and the enhanced thermal nocifensive behavior but not the mechanical nocifensive behavior were significantly reduced in ION-CCI rats. The enhanced background activities, afterdischarges and responses of wide dynamic range neurons to noxious mechanical and thermal stimulation in ION-CCI rats were significantly depressed following i.t. administration of PD98059, whereas responses to non-noxious mechanical and thermal stimulation were not altered. The present findings suggest that pERK-IR neurons in the Vc play a pivotal role in the development of thermal hypersensitivity in the face following trigeminal nerve injury.     

Antagonistic effect of enterocin CCM 4231 from Enterococcus faecium on “bryndza”, a traditional Slovak dairy product from sheep milk

“Bryndza” is a traditional Slovak dairy product (type of soft cheese) made from sheep cheese which was ripened for 14 days. Because its manufacture, transporting and/or storing represent conditions which facilitate contamination, the effect of enterocin CCM4231 in “bryndza” was investigated with the aim to reduce the contaminant agents. “Bryndza” was divided into equal portions (50 g). The experimental sample (ES) as well as the control sample one (C1) were inoculated with Listeria innocua Li1 strain. The other control samples C2 and C3 were without Li1 strain. C3 control was selected as a reference control. ES and C2 portions were treated with purified enterocin CCM4231 in a concentration of 6400 AU/ml. Before the experimental inoculation, “bryndza” was checked for the presence of contaminant agents. The experiment lasted 1 week and the samples were stored in the refrigerator at 4 °C. Sampling was performed on day 1, on day 4 and on day 7. The control samples C2 and C3 were checked only on day 1 and then after 1 week. The following contaminant agents were detected in “bryndza” before its experimental inoculation with L. innocua Li1 strain: Escherichia coli in the amount 10³ cfu/ml/g, Staphylococcus aureus (10² cfu/ml/g) and enterococci (10⁴ cfu/ml/g). In the control sample C2, the number of E. coli was reduced to 10² cfu/ml/g. Enterococci and staphylococci were totally eliminated there. Concerning C3 control, natural decrease of bacteria was found and/or their unchanged counts. The value of pH (5) was stable during the whole experiment. In the experimental sample inoculated with Li1 strain, its counts were decreased immediately after enterocin CCM4231 addition approximately by one order of magnitude. This inhibitory effect was also detectable on day 4 by the difference of one order of magnitude between ES and C1. On day 7, 10³ cfu/ml/g of Li1 strain were detected in both samples (ES, C1). The difference by one order of magnitude indicated, an inhibitory effect of enterocin CCM4231 in “bryndza”. However, bacteriocin activity was not determined by laboratory analyses.     

大鼠杏仁核簇与痛觉调制的关系

目的：研究伤害性刺激对大鼠杏仁核簇中各亚核痛反应神经元电活动的影响。方法：用串电脉冲刺激坐骨神经作为伤害性刺激,用玻璃微电极引导神经元放电。结果：杏仁核簇中多个亚核均存在痛反应神经元。伤害性刺激使痛兴奋神经元(PEN)诱发放电频率增加;使痛抑制神经元(PIN)诱发放电频率降低,并出现放电频率极低现象;两类神经元电活动相互配合。腹腔注射吗啡(10mg／kg)可以对抗伤害性刺激对痛反应神经元的作用。结论：杏仁核簇中的部分亚核在感受、整合和传递痛觉信息方面起一定作用,是中枢神经系统控制和处理痛觉信息的一个组成部分。     

Spontaneous Activity and Responses to Sensory Stimulation in Ventrobasal Thalamic Neurons in the Rat: An In Vivo Intracellular Recording and Staining Study

Spontaneous activity and responses to sensory stimulation in ventrobasal (VB) thalamic neurons were studied in barbiturate-anesthetized rats through intracellular recordings. The recordings were carried out with micropipettes filled with K acetate, KCl plus horseradish peroxidase (HRP), our KCl plus biocytin. Two types of spontaneous depolarizing events were observed: fast potentials (FPs), characterized by a low amplitude (5.3 ± 1.8 mV [mean and standard deviation]), a fast rising slope (1.15 ± 0.19 msec), and a short duration (8.47 ± 0.89 msec); and slow potentials (SPs), characterized by a larger and more variable amplitude (9.1 ± 5.6 mV) and a longer duration (62.5 ± 27.2 msec), with a slower rising slope (26.2 ± 6.4 msec). The potential changes elicited by sensory stimuli delivered manually were similar to those elicited by electronically gated short air jets to the receptive fields. FPs were evoked by sensory stimulation in 62.7% of the recorded neurons, and SPs in the remaining 37.3%. Both types of events could occur spontaneously in the same neuron, but only one of them was triggered by stimulation of the receptive field. Five neurons that were successfully stained with either HRP or biocytin were studied in detail. AH were medium-sized stellate cells, with spine-like appendages sparsely distributed along slender radiating dendrites. The axons took a rostrolateral course across the VB, and all but one left one or two thin collaterals in the reticular thalamic nucleus. No overt morphological differences were observed between VB neurons that responded with FPS or SPs to sensory stimulation.     

Cytological analysis of partial and total X-chromosome loss induced by X-rays in oocytes of Drosophila melanogaster

With the aid of a cytological technique (analysis of metaphase chromosomes of larval cerebral ganglia) it was shown that, in experiments on X-chromosome loss induced by X-rays in oocytes of Drosophila melanogaster, one has to distinguish between partial and total chromosome loss. For this purpose a scheme has been devised allowing the detection of aberrant F₁ individuals already at the larval stage. After treatment of mature oocytes, X-chromosomal fragments of various sizes were found. On the other hand, most of the X-chromosomal fragments observed after irradiation of immature oocytes had the same size as chromosome IV (“points”). Possibly this finding is, partly at least, simulated by the combined induction of complete X loss and nondisjunction of chromosomes IV. Otherwise preferential breakage close to the X-chromosomal centromere after irradiation of immature oocytes would have to be assumed to account for the observation of “points”.

About 39% (13/33) of the losses induced in mature oocytes by 400 R were shown to be partial ones. Depending on the classification of the “points” observed after treatment of immature oocytes with 3500 R, between 7% (3/43) and 23% (10/43) of the losses were partial ones. No indication was obtained either after irradiation of mature or of immature oocytes that the loss frequencies observed for imagoes and larvae differed from each other, e.g. because of selection.

The two-track component of the dose-effect curve of X-ray-induced (total plus partial) X-chromosome loss seems to be based—completely in the mature, partly in the immature oocyte experiments—on the induction of partial losses requiring two independently produced breaks.     

Temperature- and touch-sensitive neurons couple CNG and TRPV channel activities to control heat avoidance in Caenorhabditis elegans

Background

Any organism depends on its ability to sense temperature and avoid noxious heat. The nematode Caenorhabditis elegans responds to noxious temperatures exceeding ∼35°C and also senses changes in its environmental temperature in the range between 15 and 25°C. The neural circuits and molecular mechanisms involved in thermotaxis have been successfully studied, whereas details of the thermal avoidance behavior remain elusive. In this work, we investigate neurological and molecular aspects of thermonociception using genetic, cell biological and physiological approaches.

Methodology/Principal Findings

We show here that the thermosensory neurons AFD, in addition to sensing temperature within the range within which the animals can thrive, also contribute to the sensation of noxious temperatures resulting in a reflex-like escape reaction. Distinct sets of interneurons are involved in transmitting thermonociception and thermotaxis, respectively. Loss of AFD is partially compensated by the activity of a pair of multidendritic, polymodal neurons, FLP, whereas laser ablation of both types of neurons abrogated the heat response in the head of the animals almost completely. A third pair of heat sensory neurons, PHC, is situated in the tail. We find that the thermal avoidance response requires the cell autonomous function of cGMP dependent Cyclic Nucleotide-Gated (CNG) channels in AFD, and the heat- and capsaicin-sensitive Transient Receptor Potential Vanilloid (TRPV) channels in the FLP and PHC sensory neurons.

Conclusions/Significance

Our results identify distinct thermal responses mediated by a single neuron, but also show that parallel nociceptor circuits and molecules may be used as back-up strategies to guarantee fast and efficient responses to potentially detrimental stimuli.     

A comparison of eating habits between retired or semi-retired aged subjects and younger subjects in full-time work

An analysis of eating habits in older retired subjects (“No Work group”) and younger subjects employed in full-time work (“Work group”) has been carried out. It used a questionnaire that assessed why individuals chose to eat or not to eat meals during the course of the day, and subjective responses to the meals. The questionnaire was answered every three hours over a “typical week” which, for the Work group, entailed working during the weekdays and resting at the weekend. For the “No Work” group, breakfast was the most frequently taken meal of the day whereas, for the “Work” group, this meal was often missed. Patterns of meal intake were not significantly different between the weekdays and weekend for the “No Work” group, but the “Work” group ate more hot food at the weekend. The reasons cited for eating/not eating a meal and for choosing the type of meal eaten were dominated by hunger/lack of hunger in both groups. In addition, whereas habits were also important for the “No Work” group, it was time availability or the lack of it that was of major importance to the Work group, though this was significantly less important at the weekend. Meals which required more time for preparation and cooking were appreciated significantly more (appetite before the meal, enjoyment during it, and satiety afterwards) than meals such as snacks and cold food, which could be prepared more quickly. Some implications of these results, with regard to regular meals acting as a social zeitgeber in older subjects and the additional constraints imposed upon night workers, are considered.