Response Properties of TMJ Units in Superficial Laminae at the Spinomedullary Junction of Female Rats Vary Over the Estrous Cycle

2003 ◽  
Vol 89 (3) ◽  
pp. 1467-1477 ◽  
Author(s):  
K. Okamoto ◽  
H. Hirata ◽  
S. Takeshita ◽  
D. A. Bereiter
Keyword(s):  
Estrous Cycle ◽  
Dynamic Range ◽  
Response Duration ◽  
Female Rats ◽  
Mustard Oil ◽  
Cervical Cord ◽  
High Threshold ◽  
Sample Population ◽  
Upper Cervical ◽  
Nociceptive Input

Neurons responsive to stimulation of the temporomandibular joint (TMJ) region were recorded from superficial laminae at the trigeminal subnucleus caudalis/upper cervical cord (Vc/C2) junction region of cycling female rats under barbiturate anesthesia. To determine if receptive field (RF) properties or sensitivity to algesic chemicals of TMJ units vary over the estrous cycle, animals were selected from proestrous (high estrogen) or early diestrous (low estrogen) stages. More than 90% of TMJ units from each group received convergent nociceptive input [wide dynamic range (WDR) or nociceptive specific (NS)-like] from facial skin. The cutaneous high-threshold RF areas of WDR units from proestrous rats were 30% larger than diestrous units, while RF areas of NS units were similar. Bradykinin (BK, 0.1–10 μM) injection into the TMJ region excited a high percentage of units (>80% of total) from both groups in a dose-related manner. However, BK-evoked response magnitude ( R mag, +140%) and duration (+64%) were greater for proestrous than diestrous units. Both WDR and NS-like TMJ units of proestrous females displayed enhanced BK-evoked R mag values and response duration. Glutamate or mustard oil excitation of TMJ units was not affected by stage of the estrous cycle. Several TMJ units from proestrous and diestrous females were activated antidromically from the contralateral posterior thalamus, indicating that projection and nonprojection units were included in the sample population. These results were consistent with the hypothesis that factors related to stage of the estrous cycle modify the processing of deep craniofacial inputs by superficial dorsal horn neurons at the spinomedullary junction, a key region for the initial integration of sensory signals from the TMJ.

Intensity Coding by TMJ-Responsive Neurons in Superficial Laminae of Caudal Medullary Dorsal Horn of the Rat

2001 ◽  
Vol 86 (5) ◽  
pp. 2393-2404 ◽  
Author(s):  
S. Takeshita ◽  
H. Hirata ◽  
D. A. Bereiter
Keyword(s):  
Dynamic Range ◽  
Direct Injection ◽  
Joint Space ◽  
Dose Effect ◽  
Male Rats ◽  
Mustard Oil ◽  
Cervical Cord ◽  
Facial Skin ◽  
Medullary Dorsal Horn ◽  
Upper Cervical

Temporomandibular disorders (TMD) represent a family of recurrent conditions that often cause pain in the temporomandibular joint (TMJ) region and muscles of mastication. To determine if TMJ-responsive neurons encoded the intensity of pro-inflammatory chemical signals, dose-effect relationships were assessed after direct injection bradykinin into the joint space and compared with responses after injection of glutamate or saline. Neurons were recorded from superficial laminae of the trigeminal subnucleus caudalis/upper cervical cord junction region (Vc/C2) and identified by palpation of the TMJ region in barbiturate-anesthetized male rats. The majority (62 of 84) of units received convergent input from facial skin, while 26% were driven only by deep input from the TMJ region. Conduction-velocity based on the latency to firing after electrical stimulation of the TMJ region indicated 64% of units were driven by A-delta fiber input only. Bradykinin (0.1–10 μM) excited 69% of neurons tested, and 70% (19 of 27) of these units were activated by the lowest dose (0.1 μM). Glutamate (50–200 mM) excited 27% of units; however, when tested after bradykinin, 58% of units were activated by glutamate. Some TMJ units (17%) were excited by saline injection alone and not enhanced further by bradykinin or glutamate. Most (88%) TMJ units were activated by injection of the small fiber excitant, mustard oil (20% solution), into the TMJ region. Units responsive to bradykinin or glutamate were not restricted to particular classes [e.g., wide dynamic range (WDR), nociceptive specific (NS), deep only]. A small percentage of TMJ units (∼15%) were activated antidromically from the contralateral posterior thalamus. In parallel studies using c- fos immunocytochemistry, bradykinin (1 μM) injection into the TMJ region produced a greater number of Fos-positive neurons at the Vc/C2 region than glutamate (200 mM) or saline. These results revealed two broad classes of TMJ units that encoded the intensity of pro-inflammatory chemical stimuli applied to the TMJ region, units that received convergent nociceptive input from facial skin (i.e., WDR and NS units) and units that responded only to deep input from the TMJ region. On the basis of encoding properties and efferent projection status, it is concluded that activation of TMJ units within the superficial laminae at the Vc/C2region contribute to the diffuse and spreading nature of TMD pain sensation.

Differential Effects of Estradiol on Encoding Properties of TMJ Units in Laminae I and V at the Spinomedullary Junction in Female Rats

2007 ◽  
Vol 98 (6) ◽  
pp. 3242-3253 ◽  
Author(s):  
A. Tashiro ◽  
K. Okamoto ◽  
S. B. Milam ◽  
D. A. Bereiter
Keyword(s):  
Dynamic Range ◽  
Female Rats ◽  
Male Rats ◽  
Receptor Protein ◽  
Cervical Cord ◽  
P2x3 Receptors ◽  
Upper Cervical ◽  
17Β Estradiol ◽  
Wdr Neurons ◽  
To Receive

To determine whether estrogen status modulated dorsal horn neural activity relevant to temporomandibular joint (TMJ) processing single units were recorded in superficial and deep laminae at the trigeminal subnucleus caudalis/upper cervical cord (Vc/C1–2) junction of ovariectomized (OvX) female rats under barbiturate anesthesia after 17β-estradiol (E2) treatment for 2 days. E2 dose-dependently enhanced the response to intra-TMJ stimulation by adenosine triphosphate (ATP) of neurons classified as nociceptive specific (NS), but not wide dynamic range (WDR), in superficial laminae. ATP caused similar responses among NS and WDR neurons from deep laminae in all groups. By contrast, the cutaneous receptive field areas of WDR, but not NS, units in superficial and deep laminae were enlarged in high E2-treated (HE2) compared with low E2-treated (LE2) females. Units from untreated or vehicle-treated male rats displayed responses similar to those of LE2 females. TMJ units in superficial laminae from females were more likely to receive convergent cutaneous input and respond to jaw movement than males, independent of E2 treatment. Western blot analysis revealed similar levels of P2X2 and P2X3 receptor protein in Vc/C1–2 or trigeminal ganglion samples in all groups. Immunohistochemistry revealed dense terminal labeling for P2X3 receptors in superficial laminae and moderate labeling in deep laminae at the Vc/C1–2 junction. These data indicated a significant linkage between estrogen status and the magnitude of articular input evoked by ATP from TMJ neurons in the superficial laminae at the Vc/C1–2 junction, whereas estrogenic modulation of TMJ neurons in deep laminae affected only the convergent input from overlying facial skin.

Neck muscle and trigeminal input to the upper cervical cord and lower medulla of the cat

1979 ◽  
Vol 57 (6) ◽  
pp. 642-651 ◽  
Author(s):  
V. C. Abrahams ◽  
G. Anstee ◽  
F. J. R. Richmond ◽  
P. K. Rose
Keyword(s):  
Muscle Afferents ◽  
Ventral Horn ◽  
Cervical Cord ◽  
High Threshold ◽  
Neck Muscle ◽  
Afferent Projections ◽  
Muscle Afferent ◽  
Upper Cervical ◽  
Deep Layers ◽  
Neck Muscle Afferents

Experiments on chloralose-anaesthetized cats have shown that low-threshold neck muscle afferents project to laminae IV and V in the dorsal horn of the upper cervical cord, to lamina VI including the region which encompasses the central cervical nucleus, as well as to extensive regions of the ventral horn. At posterior medullary levels projections also exist to laminae IV, V, and VI of the spinal nucleus of V (although those to lamina IV are circumscribed), to the deep layers and lateral margin of the cuneate nucleus, and to the inferior olive. These projections are both from low- and high-threshold afferents. Evidence of a functional relationship between the trigeminal and neck muscle afferent system was found both in the upper cervical cord and lower medulla. About 40% of units in both regions receive a convergent input and when convergence could not be demonstrated, prior stimulation of one modality in some instances affected the responsiveness of the unit to the other modality. A motor role was found for some trigeminal afferent projections to the upper cervical cord. Trigeminal afferents consistently activated antidromically identified motoneurons of splenius, biventer cervicis, and complexus.

Position of Spinothalamic Tract Axons in Upper Cervical Spinal Cord of Monkeys

2000 ◽  
Vol 84 (3) ◽  
pp. 1180-1185 ◽  
Author(s):  
Xijing Zhang ◽  
Christopher N. Honda ◽  
Glenn J. Giesler
Keyword(s):  
Spinal Cord ◽  
Dorsal Horn ◽  
Dynamic Range ◽  
Cervical Spinal Cord ◽  
High Threshold ◽  
Spinothalamic Tract ◽  
Antidromic Activation ◽  
Lateral Funiculus ◽  
Upper Cervical ◽  
Low Threshold

Percutaneous upper cervical cordotomy continues to be performed on patients suffering from several types of severe chronic pain. It is believed that the operation is effective because it cuts the spinothalamic tract (STT), a primary pathway carrying nociceptive information from the spinal cord to the brain in humans. In recent years, there has been controversy regarding the location of STT axons within the spinal cord. The aim of this study was to determine the locations of STT axons within the spinal cord white matter of C2 segment in monkeys using methods of antidromic activation. Twenty lumbar STT cells were isolated. Eleven were classified as wide dynamic range neurons, six as high-threshold cells, and three as low-threshold cells. Eleven STT neurons were recorded in the deep dorsal horn and nine in superficial dorsal horn. The axons of the examined neurons were located at antidromic low-threshold points (<30 μA) within the contralateral lateral funiculus of C2. All low-threshold points were located ventral to the denticulate ligament, within the lateral half of the ventral lateral funiculus (VLF). None were found in the dorsal half of the lateral funiculus. The present findings support our previous suggestion that STT axons migrate ventrally as they ascend the length of the spinal cord. Also, the present findings indicate that surgical cordotomies that interrupt the VLF in C2 likely disrupt the entire lumbar STT.

Responses of Rat Spinal Dorsal Horn Neurons to Intracutaneous Microinjection of Histamine, Capsaicin, and Other Irritants

1997 ◽  
Vol 77 (5) ◽  
pp. 2499-2514 ◽  
Author(s):  
E. Carstens
Keyword(s):  
Dorsal Horn ◽  
Spinal Dorsal Horn ◽  
Dynamic Range ◽  
Mustard Oil ◽  
High Threshold ◽  
Dorsal Horn Neurons ◽  
Spinal Dorsal ◽  
Range Type ◽  
The Mean ◽  
Spinal Dorsal Horn Neurons

Carstens, E. Responses of rat spinal dorsal horn neurons to intracutaneous microinjection of histamine, capsaicin, and other irritants. J. Neurophysiol. 77: 2499–2514, 1997. To investigate the spinal processing of cutaneous pruritic and algesic stimuli, single-unit recordings were made from wide-dynamic-range-type lumbar spinal dorsal horn neurons in pentobarbital-sodium-anesthetized rats. Neuronal responses were recorded to mechanical and noxious thermal stimuli, as well as to microinjection (1 μl) of histamine (0.01–10% = 9 × 10−1–9 × 10−4 M), capsaicin (0.1% = 3.3 × 10−3 M), or other algesic chemicals into skin within the receptive field via intracutaneously placed needles. Most (84%) of the 89 neurons responded to intracutaneous (ic) microinjection of histamine with a brief phasic discharge followed by an afterdischarge of variable (s to min) duration. Ten minutes after ic microinjection of histamine (but not NaCl), there was a significant increase in the mean area of the low-threshold (but not high-threshold) portion of unit mechanical receptive fields. However, responses to graded pressure stimuli were not significantly affected after histamine. Responses did not exhibit significant tachyphylaxis when histamine microinjections were repeated at 5- or 10-min intervals. Unit responses significantly increased in a dose-related manner to microinjection of histamine at concentrations ranging across 4 orders of magnitude. Within 30 s after ic microinjection of the H1 antagonist cetirizine, unit responses to ic histamine delivered at the same skin site were significantly attenuated. Unit responses to histamine, as well as to noxious thermal stimulation, were significantly reduced after systemic administration of morphine (3.5 mg/kg ip) in a naloxone-reversible manner. Application of a mechanical rub, scratch, or a noxious heat stimulus during the unit's ongoing response to ic histamine produced a brief and marked excitation, often followed by a period of reduced ongoing discharge. Unit responses to histamine were markedly suppressed by electrical stimulation in the midbrain periaqueductal gray. Most (79%) histamine-responsive units tested also responded to ic microinjection of capsaicin. After the initial microinjection of capsaicin, subsequent responses to histamine and capsaicin microinjections were significantly reduced. Units also responded to ic ethanol (capsaicin vehicle) in a dose-related manner, and showed tachyphylaxis to repeated ic ethanol at 80% but not at 8%. The mean response to 80% ethanol was significantly smaller than to 0.1% capsaicin. All units tested also responded to topical application of mustard oil (50%) and ic serotonin (30 μg). The results are discussed in terms of theories that attempt to reconcile psychophysical and clinical observations of pain and itch sensation.

Shifts in preferred learning strategy across the estrous cycle in female rats

2004 ◽  
Vol 45 (5) ◽  
pp. 330-338 ◽  
Author(s):  
Donna L Korol ◽  
Emily L Malin ◽  
Kristine A Borden ◽  
Rachel A Busby ◽  
Julia Couper-Leo
Keyword(s):  
Estrous Cycle ◽  
Learning Strategy ◽  
Female Rats
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