Thermoreceptive neurons in the dorsal portion of the trigeminal principal nucleus in rats.

The dorsal margin of the trigeminal principal nucleus (PV) contains neurons responsive to innocuous thermal stimulation of the tongue and maybe a thermal relay (Hayama and Hashimoto, 2011). The present electrophysiological study examined whether PV thermoreceptive neurons project to the thalamus and investigated response properties to cold (20°C) or warm (40°C) stimulation of the tongue. Twenty-three thermoreceptive neurons were identified in the dorsal portion of the PV. Twenty of the 23 neurons were examined but none projected to the thalamus. Impulse frequencies of 8 of the 11 thermoreceptive neurons examined rapidly increased with cold stimulation, then decreased and gradually increased to steady state level, and rapidly decreased with warm stimulation. Thermal receptive fields were examined for six PV thermoreceptive neurons; five had a large receptive field extending over the whole anterior tongue ipsilateral to the recording side. These findings suggest that the dorsal portion of the PV is not a thermal relay mediating thermal information from the tongue to the thalamus.

Evaluación de los sistemas de medición de la fuerza muscular en el ámbito de la práctica musical. Aproximación a un prototipo apto para la práctica instrumental / Evaluation of the systems for measuring muscle strength applied to musical practice. Approach to a prototype suitable for instrumental practice

Objetivo: Evaluar los sistemas de medida de la fuerza, en tiempo real, que ejerce la mano sobre el instrumento al tocar (piano y guitarra) y conocer la fuerza ejercida por la mano del músico, en tiempo real, sobre el instrumento. Material y Método: Se analizaron sobre el instrumento, en un guitarrista y un pianista experimentados. En cada sistema analizado se valoró: el grado de interferencia con el gesto técnico musical; la posibilidad de intercambiarlo de un instrumento a otro; la resistencia al deterioro con el uso (especialmente al trabajar sobre cuerdas); la existencia de un sistema y software de captura y análisis de los datos que permitiera al usuario definir alarmas o niveles de alerta útiles para poder hacer un trabajo de reeducación de la tensión utilizada para tocar (biofeedback). Se estableció un protocolo de pruebas y se experimentó sobre ambos instrumentos. Con el método que dio mejor resultado se procedió al estudio de la fuerza ejercida por la mano del músico sobre el instrumento. Resultados: Las medidas recogidas mostraron en el caso de la guitarra un pico de fuerza máximo de 9,14N (0,93Kg) y en el piano se superaban habitualmente los 9,8N (1kg de fuerza). Conclusiones: Los sensores de presión miniaturizados recubiertos con una funda de látex ultrafino han resultado ser eficaces para el estudio de la fuerza isométrica y concéntrica desarrollada por la mano del músico (AU)

Objetive: determine, in real time, its usefulness in the study of the force exerted by the hand of the musician on the instrument (piano and guitar) and the force exerted by the hand of the musician on the instrument, in real time. Material and methods: systems better adapted to the requirements of musical practice were chosen and analyzed on the instrument, using as experimental subjects a guitarist and a pianist. For every system examined the following was considered: the degree of interference with the musical technical act; easiness to swap the system from one instrument to another; resistance to deterioration with use (especially working on strings) and existence of a system and software to capture and analyze data that allow the user to set alarms or alert levels that will help him to do reeducation of the tension used to play (biofeedback) were analysed. Results: The guitar measures showed a maximum peak force of 9.14 N (0.93Kg) and the piano usually exceeded 9.8 N (1kg force). The other analized systems (thermal imaging, Chronopic, EMG and accelerometer) let us study the force, however important limiting factors behaved they were discarded. Conclusions: Miniature pressure sensors coated with an ultrathin latex sheath have proved effective for the study of the isometric and concentric force developed by the hand of the musician (AU)

Sensory stimulation to improve swallowing reflex and prevent aspiration pneumonia in elderly dysphagic people.

Morbidity and mortality from aspiration pneumonia continues to be a major health problem in the elderly. A swallowing disorder, such as a delayed triggering of the swallowing reflex, exists in patients with aspiration pneumonia. We found that the swallowing reflex in elderly people was temperature-sensitive. The swallowing reflex was delayed when the temperature of the food was close to body temperature. The actual swallowing time shortened when the temperature difference increases. The improvement of swallowing reflex by temperature stimuli could be mediated by the temperature-sensitive transient receptor potential (TRP) channel. The administration of a pastille with capsaicin as an agonist stimulus of TRPV1, a warm-temperature receptor, decreased the delay in swallowing reflex. Food with menthol, an agonist of TRPM8, a cold-temperature receptor, also decreased the delay in swallowing reflex. Olfactory stimulation such as black pepper was useful to improve the swallowing reflex for people with low activity of daily living (ADL) levels or with decreased consciousness. Oral care also shortened the latent time of swallowing reflex presumably due to stimulating the nociception of the oral cavity. A combination of these sensory stimuli may improve the swallowing disorders and prevent aspiration pneumonia.

Does skin moisture influence the blood flow response to local heat? A re-evaluation of the Pennes model.

Pennes first described a model of heat transfer through the limb based only on calories delivered from a heat source, calories produced by metabolism and skin blood flow. The purpose of this study was to determine the effect of a moist versus a dry heat source on the skin in eliciting a blood flow response to add data to this model. Ten subjects were examined, both male and female, with a mean age of 32.5 +/- 11.6 years, mean height of 172.8 +/- 12.3 cm, and mean weight of 77.6 +/- 19.5 kg. Skin temperature was measured by a thermocouple placed on the skin and skin blood flow measured by a laser Doppler flow meter. The results of the experiments using a dry heat pack (commercially available chemical 42 degrees C cell dry heat source), moist hydrocollator pack (72.8 degrees C) separated from the skin by eight layers of towels, and whirlpool at 40 degrees C, showed that moist heat caused a significantly higher skin blood flow (about 500% greater) than dry heat (p < 0.01). Most of the greater increase in skin blood flow with moist heat was due to the greater rate of rise of skin temperature with moist versus dry heat while some of the increase in blood flow was due to the moisture itself. This could either be related to the greater heat flux across the skin with moist air or due to changing the ionic environment around skin thermo receptors by keeping the skin moist during heating. Skin thermo receptors are believed to be temperature sensitive calcium gated channels in endothelial cells which couple calcium influx to a release of nitric oxide. If true, reducing moisture in the skin might have the effect of altering ionic flux through these receptors. A correct model of skin heat flux should therefore take heat moisture content into consideration.

Zebrafish TRPA1 channels are required for chemosensation but not for thermosensation or mechanosensory hair cell function.

Transient receptor potential (TRP) ion channels have been implicated in detecting chemical, thermal, and mechanical stimuli in organisms ranging from mammals to Caenorhabditis elegans. It is well established that TRPA1 detects and mediates behavioral responses to chemical irritants. However, the role of TRPA1 in detecting thermal and mechanical stimuli is controversial. To further clarify the functions of TRPA1 channels in vertebrates, we analyzed their roles in zebrafish. The two zebrafish TRPA1 paralogs are expressed in sensory neurons and are activated by several chemical irritants in vitro. High-throughput behavioral analyses of trpa1a and trpa1b mutant larvae indicate that TRPA1b is necessary for behavioral responses to these chemical irritants. However, TRPA1 paralogs are not required for behavioral responses to temperature changes or for mechanosensory hair cell function in the inner ear or lateral line. These results support a role for zebrafish TRPA1 in chemical but not thermal or mechanical sensing, and establish a high-throughput system to identify genes and small molecules that modulate chemosensation, thermosensation, and mechanosensation.

Cold immersion recovery responses in the diabetic foot with neuropathy.

The aim of this article was to investigate the effectiveness of testing cold immersion recovery responses in the diabetic foot with neuropathy using a contact thermography system based on thermochromic liquid crystals. A total of 81 subjects with no history of diabetic foot ulceration were assigned to neuropathy, non neuropathy and healthy groups. Each group received prior verbal and written description of the test objectives and subsequently underwent a comprehensive foot care examination. The room temperature and humidity were consistently maintained at 24 degrees C and less than 50%, respectively, with air conditioning. The right foot for each subject was located on the measurement platform after cold immersion in water at 18-20 degrees C. Whole-field thermal images of the plantar foot were recorded for 10 minutes. Patients with diabetes with neuropathy show the highest 'delta temperature', that is difference between the temperature after 10-minute recovery period and baseline temperature measured independently at all the three sites tested, that is first metatarsal head (MTH), second MTH and heel. This clinical study showed for the first time the evidence of poor recovery times for the diabetic foot with neuropathy when assessing the foot under load. A temperature deficit (because of poor recovery to baseline temperature) suggests degeneration of thermoreceptors, leading to diminished hypothalamus-mediated activity in the diabetic neuropathic group.

TRPA1 mediates the inflammatory actions of environmental irritants and proalgesic agents.

TRPA1 is an excitatory ion channel targeted by pungent irritants from mustard and garlic. TRPA1 has been proposed to function in diverse sensory processes, including thermal (cold) nociception, hearing, and inflammatory pain. Using TRPA1-deficient mice, we now show that this channel is the sole target through which mustard oil and garlic activate primary afferent nociceptors to produce inflammatory pain. TRPA1 is also targeted by environmental irritants, such as acrolein, that account for toxic and inflammatory actions of tear gas, vehicle exhaust, and metabolic byproducts of chemotherapeutic agents. TRPA1-deficient mice display normal cold sensitivity and unimpaired auditory function, suggesting that this channel is not required for the initial detection of noxious cold or sound. However, TRPA1-deficient mice exhibit pronounced deficits in bradykinin-evoked nociceptor excitation and pain hypersensitivity. Thus, TRPA1 is an important component of the transduction machinery through which environmental irritants and endogenous proalgesic agents depolarize nociceptors to elicit inflammatory pain.

Lessons from peppers and peppermint: the molecular logic of thermosensation.

Sensory neurons report a wide range of temperatures, from noxious heat to noxious cold. Natural products that elicit psychophysical sensations of hot or cold, such as capsaicin or menthol, were instrumental in the discovery of thermal detectors belonging to the transient receptor potential (TRP) family of cation channels. Studies are now beginning to reveal how these channels contribute to thermosensation and how chemical signaling pathways, such as those activated by tissue injury, alter thermal sensitivity through TRP channel modulation. Analysis of TRP channel expression among sensory neurons is also providing insight into how thermal stimuli are encoded by the peripheral nervous system.

Identification of a cold receptor reveals a general role for TRP channels in thermosensation.

The cellular and molecular mechanisms that enable us to sense cold are not well understood. Insights into this process have come from the use of pharmacological agents, such as menthol, that elicit a cooling sensation. Here we have characterized and cloned a menthol receptor from trigeminal sensory neurons that is also activated by thermal stimuli in the cool to cold range. This cold- and menthol-sensitive receptor, CMR1, is a member of the TRP family of excitatory ion channels, and we propose that it functions as a transducer of cold stimuli in the somatosensory system. These findings, together with our previous identification of the heat-sensitive channels VR1 and VRL-1, demonstrate that TRP channels detect temperatures over a wide range and are the principal sensors of thermal stimuli in the mammalian peripheral nervous system.

Behavioral state-dependent thermal feedback influencing the hypothalamic thermostat.

The experimental evidence on the behavioral state-dependent compartmentalization of temperature in the central nervous system of three homeothermic species has been reviewed to address the question of how selective brain cooling influences hypothalamic temperature regulation.

Thermosensitivity of the lobster, Homarus americanus, as determined by cardiac assay.

It is generally accepted that crustaceans detect, and respond to, changes in water temperature, yet few studies have directly addressed their thermosensitivity. In this investigation a cardiac assay was used as an indicator that lobsters (Homarus americanus) sensed a change in temperature. The typical cardiac response of lobsters to a 1-min application of a thermal stimulus, either warmer (n = 19) or colder (n = 17) than the holding temperature of 15 degrees C, consisted of a short bradycardia (39.5 +/- 8.0 s) followed by a prolonged tachycardia (188.2 +/- 10.7 s). Lobsters exposed to a range of rates of temperature change (0.7, 1.4, 2.6, 5.0 degrees C/min) responded in a dose-dependent manner, with fewer lobsters responding at slower rates of temperature change. The location of temperature receptors could not be determined, but lesioning of the cardioregulatory nerves eliminated the cardiac response. Although the absolute detection threshold is not known, it is conservatively estimated that lobsters can detect temperature changes of greater than 1 degree C, and probably as small as 0.15 degrees C. A comparison of winter and summer lobsters, both held at 15 degrees C for more than 4 weeks, revealed that although their responses to temperature changes were similar, winter lobsters (n = 18) had a significantly lower baseline heart rate (34.8 +/- 4.4 bpm) and a shorter duration cardiac response (174 s) than summer lobsters (n = 18; 49.9 +/- 5.0 bpm, and 320 s respectively). This suggests that some temperature-independent seasonal modulation of cardiac activity may be occurring.

Developmental and hormonal regulation of thermosensitive neuron potential activity in rat brain.

To understand the involvement of thyroid hormone on the postnatal development of hypothalamic thermosensitive neurons, we focused on the analysis of thermosensitive neuronal activity in the preoptic and anterior hypothalamic (PO/AH) regions of developing rats with and without hypothyroidism. In euthyroid rats, the distribution of thermosensitive neurons in PO/AH showed that in 3-week-old rats (46 neurons tested), 19.5% were warm-sensitive and 80.5% were nonsensitive. In 5- to 12-week-old euthyroid rats (122 neurons), 33.6% were warm-sensitive and 66.4% were nonsensitive. In 5- to 12-week-old hypothyroid rats (108 neurons), however, 18.5% were warm-sensitive and 81.5% were nonsensitive. Temperature thresholds of warm-sensitive neurons were lower in 12-week-old euthyroid rats (36.4+/-0.2 degrees C, n = 15, p<0.01,) than in 3-week-old and in 5-week-old euthyroid rats (38.5+/-0.5 degrees C, n = 9 and 38.0+/-0.3 degrees C, n = 15, respectively). The temperature thresholds of warm-sensitive neurons in 12-week-old hypothyroid rats (39.5+/-0.3 degrees C, n = 8) were similar to that of warm-sensitive neurons of 3-week-old raats (euthyroid and hypothyroid). In contrast, there was no difference in the thresholds of warm-sensitive neurons between hypothyroid and euthyroid rats at the age of 3-5 weeks. In conclusion, monitoring the thermosensitive neuronal tissue activity demonstrated the evidence that thyroid hormone regulates the maturation of warm-sensitive hypothalamic neurons in developing rat brain by electrophysiological analysis.

A distinct thermoreceptive subregion of lamina I in nucleus caudalis of the owl monkey.

An immunohistochemically distinct zone was identified in the superficial aspect of trigeminal nucleus caudalis of the New World owl monkey that is not immunoreactive for substance P or serotonin, in stark contrast to the dense staining present in the surrounding laminae I and II. Thionin-stained sections in different planes showed that this is a subregion of lamina I containing clusters of neurons that appear to have pyramidal or polygonal somata. Extracellular microelectrode recordings in this region revealed clusters of thermoreceptive-specific (COLD) cells with nasal or labial receptive fields, whereas nociceptive neurons were found in the adjacent portions of lamina I. Anterograde tracer injections in this region produced trigeminothalamic terminal labeling in the site homologous to the lamina I spino-thalamo-cortical relay nucleus identified previously in the Old World macaque monkey and in humans. Retrograde tracer injections involving this thalamic site, where recordings of trigeminal COLD-like neurons were obtained, produced clusters of retrogradely labeled trigeminothalamic neurons in this immunohistochemically distinct subregion of lamina I, nearly all of which are pyramidal neurons. We conclude that the nocturnal owl monkey has a specialized perinasal thermoreceptive trigeminothalamic sensory pathway that is probably of behavioral significance during olfactory sniffing. In addition, these observations corroborate other findings that have indicated that lamina I COLD cells are pyramidal neurons and are not physiologically modulated by substance P or serotonin, in contrast to nociceptive neurons.

Temperature regulation during exercise.

During strenuous exercise the body's heat production may exceed 1000 W. Some of the heat produced is stored, raising body core temperature by a few degrees. Rises in body temperature are sensed by central and skin thermoreceptors and this sensory information is processed by the hypothalamus to trigger appropriate effector responses. Other sensory inputs from baroreceptors and osmoreceptors can modify these responses. Evaporation of sweat and increased skin blood flow are effective mechanisms for the dissipation of heat from the body but dehydration impairs the capacity to sweat and lose body heat. Hot, humid environments or inappropriate clothing may compromise the ability to lose heat from the body. Exercise training improves tolerance to exercise in the heat by increasing the sensitivity of the sweat rate/core temperature relationship, decreasing the core temperature threshold for sweating and increasing total blood volume.

Selective brain cooling: role of angularis oculi vein and nasal thermoreception.

We have measured blood flows in the angularis oculi (AOV), facial, and jugular veins and temperatures in the carotid artery and near the hypothalamus in three lightly anesthetized sheep while body and nasal mucosal (Tnm) temperatures were varied independently. Above a threshold hypothalamic temperature (Thyp) of 39 degrees C both selective brain cooling (SBC) and AOV blood flow increased. For a given Thyp, the increase in AOV flow and SBC was inversely proportional to Tnm: low Tnm resulted in high AOV flow and SBC, whereas increasing Tnm attenuated both AOV flow and SBC. This decrease in AOV flow results in submaximal SBC, which does not concur with the hypothesis that SBC functions to protect a thermally vulnerable brain. The trigger for these changes in AOV blood flow was Tnm. Occlusion of the AOV during SBC showed that AOV flow accounted for over 80% of SBC. We conclude that SBC is not only a mechanism for reducing brain temperature but may also be a means of adjusting Thyp to facilitate the appropriate thermoregulatory responses.

[Adaptive changes of preoptic thermosensitive neurons in hypothalamic tissue slices of rats after long-term exposure to cold environmental temperature].

In the present work, thermosensitivity and spontaneous firing rate of 86 preoptic neurons in hypothalamic tissue slices from 20 cold acclimated rats (CR, at 5 +/- 1 degrees C for more than 3 weeks) and 127 neurons from 35 warm acclimated rats (WR, at 20 +/- 3 degrees C for the same period) were recorded and compared. The results showed that: (1) The percentage of cold-sensitive neurons in CR were higher than that in WR, the critical temperature and the lowest temperature of the spontaneous firing activity of cold-sensitive neurons in CR were also lower than that in WR. (2) Thermosensitivity and critical temperature of the warm-sensitive neurons in CR were remarkably decreased, and spontaneous firing rate under 37 degrees C was increased. (3) Spontaneous firing rate (37 degrees C) of temperature insensitive neurons in CR were conspicuously increased and the lowest temperature extended downward. These profound changes in response to long-term cold exposure suggested that plasticity of preoptic neurons was involved in the thermoregulation in cold adaptation.

[The mechanisms of the temperature sensitivity of the hypothalamic neurons]. / Mekhanizmy temperaturnoi chuvstvitel'nosti neironov gipotalamusa.

Studies of the 1960-80-s in intact animals and brain slices showed the existence of brain temperature-sensitive neurons in the vertebrate hypothalamus. Increased firing rate of these units activates the thermoregulatory processes. Applications of synaptic blockade in slices, and of intracellular recordings and clamp technique in the last 3-4 years allowed to find that many hypothalamic thermosensitive neurons possess an intrinsic mechanism of temperature sensitivity central to. This mechanism is a change in ionic permeability of neuronal membrane. The review summarizes the results of these studies and considers possible causes of thermo-induced changes in ionic conductivity of hypothalamic thermosensitive neuron membrane.

Spinothalamic and spinohypothalamic tract neurons in the cervical enlargement of rats. III. Locations of antidromically identified axons in the cervical cord white matter.

1. Fifty-five neurons in the cervical enlargement (C6-C8) of urethan-anesthetized rats were antidromically activated from the contralateral posterior diencephalon. In all cases, antidromic thresholds were < or = 30 microA. The locations of the axons of these neurons within the white matter of segments C2-C6 were determined by tracking systematically using a second antidromic stimulating electrode. 2. The recording locations of 51 neurons were marked and recovered. Twenty neurons were recorded in the superficial dorsal horn (SDH) and 31 were in the deep dorsal horn (DDH). Eighty-three lowest threshold points for antidromic activation within the white matter of segments C2-C6 were determined for these 51 neurons. The mean antidromic threshold at these points was 9.5 +/- 0.5 (SE) microA. For 26 neurons, the lowest threshold point for antidromic activation was determined at one segmental level. We also attempted to determine whether individual axons maintained their position as they ascended through the cervical cord white matter. In 25 cases, lowest threshold points were determined at two or more segmental levels. 3. In segments C5-C6, 88% (7/8) of the lowest threshold points of the examined axons were located in the contralateral ventral funiculus, indicating that the majority of examined axons crossed the midline within one or two segments. 4. In segments C3-C4, 32% (14/44) of all examined axons were found in the dorsal lateral funiculus (DLF) and 66% (29/44) were within the ventral quadrant [ventral lateral funiculus (VLF) and ventral funiculus (VF)]. Sixty-nine percent (11/16) of the axons of neurons recorded in the SDH were located in the contralateral DLF and 31% (5/16) were located in the ventral quadrant (VQ). In contrast, only 11% (3/28) of the axons of neurons recorded in the DDH were located in the contralateral DLF and 86% (24/28) were located in the VQ. Therefore, in segments C3-C4, the locations of axons differed significantly. Those from neurons recorded in the SDH were located primarily in the DLF and those from neurons recorded in the DDH were located principally in the VQ. 5. In segment C2, 74% (23/31) of all examined axons were found in the DLF, 23% (7/31) were in the VQ, and 3% (1/31) were in the dorsal horn. Thus, the percentage of all examined axons in the DLF in C2 was approximately 2.5 times greater than it was in C3-C4.(ABSTRACT TRUNCATED AT 400 WORDS)

Spinothalamic and spinohypothalamic tract neurons in the cervical enlargement of rats. I. Locations of antidromically identified axons in the thalamus and hypothalamus.

1. Seventy-seven neurons in the cervical enlargement of rats anesthetized with urethan were initially antidromically activated using currents < or = 30 microA from the contralateral posterior thalamus. A goal of these experiments was to determine the course of physiologically characterized spinal axons within the diencephalon. Therefore, in 38 cases, additional antidromic mapping was done throughout the mediolateral extent of the diencephalon at multiple anterior-posterior planes. 2. Electrolytic lesions marking the recording sites were recovered for 71 neurons. Thirty-one were located in the superficial dorsal horn (SDH); 39 were in nucleus proprius or the lateral reticulated area of the deep dorsal horn (DDH), and one was in the ventral horn. 3. Eight of 38 (21%) neurons that were tested for more anterior projections could only be antidromically activated with currents < or = 30 microA from sites in the contralateral posterior thalamus. Such neurons are referred to as spinothalamic tract (STT) neurons. Lesions marking the lowest threshold points for antidromic activation were located in or near the posterior thalamic group (Po). At more anterior levels, considerably higher currents were required for antidromic activation or it was not possible to activate the neurons with currents up to 500 microA. Four of these neurons were physiologically characterized and each responded preferentially to noxious mechanical stimuli (wide dynamic range, WDR). Each of the three neurons that were tested responded to noxious heat stimuli. These findings confirm anatomic studies that have shown that a number of STT axons terminate in Po and suggest that such axons that originate in the cervical enlargement carry nociceptive input from the upper extremity. 4. In 15 cases, electrode penetrations were made systematically throughout much of the contralateral ventrobasal complex (VbC). In 17 cases, penetrations were made throughout the intralaminar nuclei contralaterally, including the central lateral nucleus (CL). Surprisingly, only one of the examined axons was antidromically activated with low currents from CL and one from VbC, although both of these nuclei are known to receive sizeable inputs from the STT. 5. Many of the axons (27 of the 38 tested, 71%) that were initially antidromically activated from the contralateral posterior thalamus could also be antidromically activated with low currents (< or = 30 microA) and at increased latencies from sites located anteriorly in the contralateral hypothalamus. Such neurons are referred to as spinothalamic tract/spinohypothalamic tract (STT/SHT) neurons.(ABSTRACT TRUNCATED AT 400 WORDS)