Physiological Studies of Spinohypothalamic Tract Neurons in the Lumbar Enlargement of Monkeys

1999 ◽  
Vol 82 (2) ◽  
pp. 1054-1058 ◽  
Author(s):  
X. Zhang ◽  
H. N. Wenk ◽  
A. P. Gokin ◽  
C. N. Honda ◽  
G. J. Giesler
Keyword(s):  
Dorsal Horn ◽  
Receptive Fields ◽  
Antidromic Activation ◽  
Response Characteristics ◽  
Nociceptive Information ◽  
Anatomic Results ◽  
Noxious Stimuli ◽  
Pass Through ◽  
Low Amplitude

Recent anatomic results indicate that a large direct projection from the spinal cord to the hypothalamus exists in monkeys. The aim of this study was to determine whether the existence of this projection could be confirmed unambiguously using electrophysiological methods and, if so, to determine the response characteristics of primate spinohypothalamic tract (SHT) neurons. Fifteen neurons in the lumbar enlargement of macaque monkeys were antidromically activated using low-amplitude current pulses in the contralateral hypothalamus. The points at which antidromic activation thresholds were lowest were found in the supraoptic decussation ( n = 13) or in the medial hypothalamus ( n = 2). Recording points were located in the superficial dorsal horn ( n = 1), deep dorsal horn ( n = 10), and intermediate zone ( n = 4). Each of the 12 examined neurons had cutaneous receptive fields on the ipsilateral hindlimb. All neurons responded exclusively or preferentially to noxious stimuli, suggesting that the transmission of nociceptive information is an important role of primate SHT axons. Twelve SHT neurons were also antidromically activated from the thalamus. In all cases, the antidromic latency from the thalamus was shorter than that from the hypothalamus, suggesting that the axons pass through the thalamus then enter the hypothalamus. These results confirm the existence of a SHT in primates and suggest that this projection may contribute to the production of autonomic, neuroendocrine, and emotional responses to noxious stimuli in primates, possibly including humans.

Physiological characterization of spinohypothalamic tract neurons in the lumbar enlargement of rats

1991 ◽  
Vol 66 (1) ◽  
pp. 261-284 ◽  
Author(s):  
R. Burstein ◽  
R. J. Dado ◽  
K. D. Cliffer ◽  
G. J. Giesler
Keyword(s):  
Dorsal Horn ◽  
Gray Matter ◽  
Mechanical Stimulation ◽  
Dynamic Range ◽  
Receptive Fields ◽  
Optic Tract ◽  
Antidromic Activation ◽  
Noxious Stimuli ◽  
Noxious Mechanical Stimulation ◽  
Stimulation Of

1. Ninety-six neurons in the lumbar enlargement of urethananesthetized rats were antidromically activated from the contralateral hypothalamus. The antidromic stimulating electrode was moved systematically within the hypothalamus until antidromic activation could be produced with currents of less than or equal to 50 microA (18.6 +/- 10.8 microA; mean +/- SD). The points at which antidromic activation thresholds were lowest were found in several regions of the hypothalamus but were concentrated in the optic tract and the supraoptic decussation. 2. The recording locations of 79 spinohypothalamic tract (SHT) neurons were marked and recovered. Twenty-nine were located in the superficial dorsal horn (SDH), 42 in the deep dorsal horn (DDH), 4 in the intermediate zone, and 2 in the gray matter surrounding the central canal. Two additional marks were located in the dorsal lateral funiculus (DLF). 3. The responses of 46 SHT neurons were examined during innocuous and noxious mechanical stimulation of their receptive fields. Forty-eight percent of recorded SHT neurons responded to both innocuous and noxious stimuli (wide dynamic range, WDR) and 39% responded only to noxious stimuli (high threshold, HT). Therefore 87% of SHT neurons responded preferentially or exclusively to noxious mechanical stimulation. Nine percent of SHT neurons responded exclusively to innocuous manipulation of joints and muscles. Four percent of SHT neurons responded only to innocuous tactile stimul (low threshold, LT). WDR, HT, and LT neurons were recorded widely throughout the dorsal horn; no relationship was found between the locations of recording sites in the dorsal horn and the response types of the neurons. SHT neurons that responded to stimulation of muscle, tendon, or joint were recorded deep in the gray matter. 4. The effects of heating the receptive fields were determined for 25 SHT neurons. Fourteen (56%) responded to thermal stimuli. Six (43%) of the responsive neurons responded at low frequencies to innocuous warming (38-41 degrees C) but more vigorously to noxious (greater than or equal to 45 degrees C) heating. The other eight responded only to noxious heat. Eighteen percent (3/17) of tested SHT neurons were activated by noxious cooling of their receptive fields. 5. Cutaneous receptive fields of most recorded SHT neurons were small, typically involving areas as small as two or three toes on the ipsilateral hindlimb; the largest receptive fields covered the entire paw. These findings indicate that relatively precise information about the location of innocuous and noxious stimuli is conveyed directly to the hypothalamus by SHT neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Response Characterstics of Spinothalamic Tract Neurons That Project to the Posterior Thalamus in Rats

2005 ◽  
Vol 93 (5) ◽  
pp. 2552-2564 ◽  
Author(s):  
Xijing Zhang ◽  
Glenn J. Giesler
Keyword(s):  
Conduction Velocity ◽  
Receptive Fields ◽  
Spinothalamic Tract ◽  
Antidromic Activation ◽  
Posterior Thalamus ◽  
Functional Roles ◽  
Nociceptive Information ◽  
Medial Geniculate ◽  
Low Amplitude ◽  
Sizeable Number

A sizeable number of spinothalamic tract axons terminate in the posterior thalamus. The functional roles and precise areas of termination of these axons have been a subject of recent controversy. The goals of this study were to identify spinothalamic tract neurons (STT) within the cervical enlargement that project to this area, characterize their responses to mechanical and thermal stimulation of their receptive fields, and use microantidromic tracking methods to determine the nuclei in which their axons terminate. Forty-seven neurons were antidromically activated using low-amplitude (≤30 μA) current pulses in the contralateral posterior thalamus. The 51 points at which antidromic activation thresholds were lowest were surrounded by ineffective tracks indicating that the surrounded axons terminated within the posterior thalamus. The areas of termination were located primarily in the posterior triangular, medial geniculate, posterior and posterior intralaminar, and suprageniculate nuclei. Recording points were located in the superficial and deep dorsal horn. The mean antidromic conduction velocity was 6.4 m/s, a conduction velocity slower than that of other projections to the thalamus or hypothalamus in rats. Cutaneous receptive fields appeared to be smaller than those of neurons projecting to other areas of the thalamus or to the hypothalamus. Each of the examined neurons responded exclusively or preferentially to noxious stimuli. These findings indicate that the STT carries nociceptive information to several target nuclei within the posterior thalamus. We discuss the evidence that this projection provides nociceptive information that plays an important role in fear conditioning.

Location and properties of dorsal horn neurons at origin of spinoreticular tract in lumbar enlargement of the rat

1980 ◽  
Vol 44 (5) ◽  
pp. 862-877 ◽  
Author(s):  
D. Menetrey ◽  
A. Chaouch ◽  
J. M. Besson
Keyword(s):  
Dorsal Horn ◽  
Receptive Fields ◽  
Radiant Heat ◽  
Mechanical Stimuli ◽  
Spinothalamic Tract ◽  
Antidromic Activation ◽  
Electrophysiological Properties ◽  
Tactile Stimuli ◽  
Adjacent Structures ◽  
Conduction Velocities

1. Spinoreticular tract neurons at the rat lumbar cord level were identified by antidromic activation following stimulation at mainly pontine and mesencephalic levels. These units, which were found in the dorsal half of the cord, could be separated into two groups according to their spinal location, electrophysiological properties, and their central projections. 2. Units in the dorsolateral funiculus nucleus projected mainly to the cuneiformis area and adjacent structures with frequent bilateral projections. They had the slowest conduction velocities, sometimes in the unmyelinated range. Generally, they were driven only by stimulation of subcutaneous and/or deep structures. 3. Neurons located in the dorsal horn mainly projected contralaterally to pontine and mesencephalic levels. their conduction velocities and the electrophysiological properties were identical to those observed for the rat spinothalamic tract (22). Almost all (86%) had clear cutaneous sensitivity and generally large receptive fields: 40% responded to nonnoxious and noxious mechanical cutaneous stimuli and frequently to noxious radiant heat, 26% were exclusively excited by light tactile stimuli, and 20% required noxious cutaneous mechanical stimulation for activation. There was a good correlation between responses to natural and transcutaneous electrical stimulation: units driven by noxious mechanical stimuli received A-delta- and/or C-fiber inputs. The remaining units (14%) had more complex receptive fields associated with both excitatory and inhibitory inputs originating from a single peripheral area. 4. The functional heterogeneity of the rat spinoreticular tract is reminiscent of that demonstrated for the rat and monkey spinothalamic tracts. Similarly, the rat spinoreticular neurons are under the influence of descending inhibitory controls originating from the nucleus raphe magnus and bulbar reticular formation. 5. Responses of the rat spinoreticular tract neurons are consistent with the involvement of this pathway in the transmission of messages of both innocuous and noxious origins.

scholarly journals Activation of spinal dorsal horn astrocytes by noxious stimuli involves descending noradrenergic signaling

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Riku Kawanabe ◽  
Kohei Yoshihara ◽  
Izuho Hatada ◽  
Makoto Tsuda
Keyword(s):  
Dorsal Horn ◽  
Spinal Dorsal Horn ◽  
Common Mechanism ◽  
Formalin Injection ◽  
Intraplantar Injection ◽  
Spinal Dorsal ◽  
Noxious Stimuli ◽  
Underlying Mechanisms

AbstractAstrocytes are critical regulators of neuronal function in the central nervous system (CNS). We have previously shown that astrocytes in the spinal dorsal horn (SDH) have increased intracellular Ca2+ levels following intraplantar injection of the noxious irritant, formalin. However, the underlying mechanisms remain unknown. We investigated these mechanisms by focusing on the role of descending noradrenergic (NAergic) signaling because our recent study revealed the essential role of the astrocytic Ca2+ responses evoked by intraplantar capsaicin. Using in vivo SDH imaging, we found that the Ca2+ level increase in SDH astrocytes induced by intraplantar formalin injection was suppressed by ablation of SDH-projecting locus coeruleus (LC)-NAergic neurons. Furthermore, the formalin-induced Ca2+ response was dramatically decreased by the loss of α1A-adrenaline receptors (ARs) in astrocytes located in the superficial laminae of the SDH. Moreover, similar inhibition was observed in mice pretreated intrathecally with an α1A-AR-specific antagonist. Therefore, activation of α1A-ARs via descending LC-NAergic signals may be a common mechanism underlying astrocytic Ca2+ responses in the SDH evoked by noxious stimuli, including chemical irritants.

Functional properties of dorsal horn neurons that project to the dorsal accessory olive

1990 ◽  
Vol 64 (6) ◽  
pp. 1704-1711 ◽  
Author(s):  
H. H. Molinari ◽  
J. O. Dostrovsky ◽  
N. el-Yassir
Keyword(s):  
Dorsal Horn ◽  
Receptive Fields ◽  
The Other ◽  
Antidromic Activation ◽  
Lumbosacral Spinal Cord ◽  
Dorsal Horn Neurons ◽  
Somatosensory Information ◽  
Gracile Nucleus ◽  
Wide Range ◽  
Average Latency

1. This study examined the responses to natural cutaneous stimuli of neurons in the dorsal horn of the lumbosacral spinal cord that project to the dorsal accessory portion of the inferior olive (DAO) in cats anesthetized with pentobarbital sodium. Extracellular activity was recorded from single units antidromically activated by currents of less than or equal to 70 muA applied to DAO. 2. A total of 119 antidromically activated neurons was examined. Their antidromic activation latencies displayed a wide range (2.5–24.6 ms). The average latency corresponds to a conduction velocity of 24 m/s. 3. Collision was demonstrated for 24 neurons. All responded to some form of natural cutaneous stimulation. Their receptive fields encompassed some portion of the hind limb, particularly the toes; one-third displayed gradients of sensitivity. 4. Based on their thresholds to peripheral stimulation, the 24 neurons fell into five categories, those sensitive to light cutaneous stimuli (i.e., hair movement or light touch; 37.5%), rub (21%), tap (21%), pressure (12.5%), or noxious stimuli (8%). 5. Comparison of these results with data on the other major source of somatosensory information for DAO, the gracile nucleus (examined previously with the same methods), suggests that the sensitivity of neurons in DAO to light cutaneous stimuli is mediated primarily by neurons in the dorsal horn. The sensitivity of neurons in DAO to tap, rub, or pressure, on the other hand, might be mediated by neurons in either the dorsal horn, the gracile nucleus, or both.

Vibrotactile Coding Capacities of Spinocervical Tract Neurons in the Cat

2006 ◽  
Vol 95 (3) ◽  
pp. 1465-1477 ◽  
Author(s):  
V. Sahai ◽  
D. A. Mahns ◽  
N. M. Perkins ◽  
L. Robinson ◽  
M. J. Rowe
Keyword(s):  
Electrical Stimulation ◽  
Receptive Fields ◽  
Dorsal Column ◽  
Vibration Frequencies ◽  
Antidromic Activation ◽  
Tactile Sensibility ◽  
Response Characteristics ◽  
Tactile Stimuli ◽  
Useful Signal ◽  
Stimulation Of

The response characteristics and tactile coding capacities of individual dorsal horn neurons, in particular, those of the spinocervical tract (SCT), have been examined in the anesthetized cat. Twenty one of 38 neurons studied were confirmed SCT neurons based on antidromic activation procedures. All had tactile receptive fields on the hairy skin of the hindlimb. Most (29/38) could also be activated transynaptically by electrical stimulation of the cervical dorsal columns, suggesting that a common set of tactile primary afferent fibers may provide the input for both the dorsal column-lemniscal pathway and for parallel ascending pathways, such as the SCT. All but 3 of the 38 neurons studied displayed a pure dynamic sensitivity to controlled tactile stimuli but were unable to sustain their responsiveness throughout 1s trains of vibration at vibration frequencies exceeding 5–10 Hz. Stimulus-response relations revealed a very limited capacity of individual SCT neurons to signal, in a graded way, the intensity parameter of the vibrotactile stimulus. Furthermore, because of their inability to respond on a cycle-by-cycle pattern at vibration frequencies >5–10 Hz, these neurons were unable to provide any useful signal of vibration frequency beyond the very narrow bandwidth of ∼5–10 Hz. Similar limitations were observed in the responsiveness of these neurons to repetitive forms of antidromic and transynaptic inputs generated by electrical stimulation of the spinal cord. In summary, the observed limitations on the vibrotactile bandwidth of SCT neurons and on the precision and fidelity of their temporal signaling, suggest that SCT neurons could serve as little more than coarse event detectors in tactile sensibility, in contrast to DCN neurons the bandwidth of vibrotactile responsiveness of which may extend beyond 400 Hz and is therefore broader by ∼40–50 times than that of SCT neurons.

Spinothalamic and spinohypothalamic tract neurons in the cervical enlargement of rats. II. Responses to innocuous and noxious mechanical and thermal stimuli

1994 ◽  
Vol 71 (3) ◽  
pp. 981-1002 ◽  
Author(s):  
R. J. Dado ◽  
J. T. Katter ◽  
G. J. Giesler
Keyword(s):  
Dorsal Horn ◽  
Dynamic Range ◽  
Receptive Fields ◽  
Ventral Horn ◽  
Zona Incerta ◽  
High Threshold ◽  
Mechanical Stimuli ◽  
Spinothalamic Tract ◽  
Noxious Stimuli ◽  
Wdr Neurons

1. The goal of this study was to gather data that would increase our understanding of nociceptive processing by spinothalamic tract (STT) neurons that receive inputs from the hand and arm. Fifty neurons in the cervical enlargement of urethan-anesthetized rats were antidromically activated from the contralateral posterior thalamus. A stimulating electrode was moved systematically within an anterior-posterior plane in the thalamus until a point was located where the smallest amount of current antidromically activated the neuron. The antidromic thresholds at each of these lowest threshold points was < or = 30 microA; the mean antidromic threshold was 15.4 +/- 1.0 (SE) microA. Lowest threshold points were found primarily in the posterior thalamic group (Po), zona incerta, and in or near the supraoptic decussation. 2. The recording sites of 47 neurons were marked and recovered. Recording sites were located in the superficial dorsal horn (SDH, n = 15), deep dorsal horn (DDH, n = 31), and ventral horn (n = 1). Recording sites were located across the mediolateral extent of the SDH. Within the DDH, recording sites were concentrated laterally in nucleus proprius and dorsally in the lateral reticulated area. The locations of the recording points confirm previous anatomic descriptions of STT neurons in the cervical enlargement. 3. Cutaneous excitatory receptive fields were restricted to the ipsilateral forepaw or forelimb in 67% (10/15) of the neurons recorded in the SDH and 42% (13/31) of the neurons recorded in the DDH. Neurons having larger, more complex receptive fields were also commonly encountered. Thirty-three percent (5/15) of the neurons recorded in the SDH and 58% (18/31) recorded in the DDH had receptive fields that were often discontinuous and included areas of the ipsilateral shoulder, thorax, and head, including the face. 4. Innocuous and noxious mechanical stimuli were applied to the receptive field of each neuron. Fifty percent (25/50) responded to innocuous mechanical stimuli but responded at higher frequencies to noxious stimuli (wide dynamic range, WDR). Forty-four percent (22/50) responded only to noxious stimuli (high threshold, HT). Six percent (3/50) responded preferentially to innocuous stimuli (low threshold, LT). WDR and HT neurons were recorded in both the SDH and DDH, including nucleus proprius, an area not typically associated with nociceptive transmission at other levels of the cord. Sixty percent (9/15) of the units recorded in the SDH were classified as WDR neurons; the other 40% (6/15) were classified HT. Forty-eight percent (15/31) of the units recorded in the DDH were classified as WDR neurons and 42% (13/31) as HT.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetaminophen Inhibits Spinal Prostaglandin E2Release after Peripheral Noxious Stimulation 

1999 ◽  
Vol 91 (1) ◽  
pp. 231-239 ◽  
Author(s):  
Uta S. Muth-Selbach ◽  
Irmgard Tegeder ◽  
Kay Brune ◽  
Gerd Geisslinger
Keyword(s):  
Spinal Cord ◽  
Urinary Excretion ◽  
Dorsal Horn ◽  
Formalin Test ◽  
Intraperitoneal Administration ◽  
Noxious Stimulation ◽  
Cyclooxygenase Inhibitor ◽  
Nociceptive Processing ◽  
Pge2 Release

Background Prostaglandin play a pivotal role in spinal nociceptive processing. At therapeutic concentrations, acetaminophen is not a cyclooxygenase inhibitor. inhibitor. Thus, it is antinociceptive without having antiinflammatory or gastrointestinal toxic effects. This study evaluated the role of spinal prostaglandin E2 (PGE2) in antinociception produced by intraperitoneally administered acetaminophen. Methods The PGE2 concentrations in the dorsal horn of the spinal cord were measured after formalin was injected into the hind paw of rats. The effect of antinociceptive doses of acetaminophen (100, 200, and 300 mg/kg given intraperitoneally) on PGE2 levels and flinching behavior was monitored Spinal PGE2 and acetaminophen concentrations were obtained by microdialysis using a probe that was implanted transversely through the dorsal horn of the spinal cord at L4. Furthermore, the effects of acetaminophen on urinary prostaglandin excretion were determined. Results Intraperitoneal administration of acetaminophen resulted in a significant decrease in spinal PGE2 release that was associated with a significant reduction in the flinching behavior in the formalin test Acetaminophen was distributed rapidly into the spinal cord with maximum dialysate concentrations 4560 min after intraperitoneal administration. Urinary excretion of prostanoids (PGE2, PGF2alpha, and 6-keto-PGF1alpha) was not significantly altered after acetaminophen administration. Conclusions The data confirm the importance of PGE2 in spinal nociceptive processing. The results suggest that antinociception after acetaminophen administration is mediated, at least in part, by inhibition of spinal PGE2 release. The mechanism, however, remains unknown. The finding that urinary excretion of prostaglandins was not affected might explain why acetaminophen is antinociceptive but does not compromise renal safety.

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