Dorsal column postsynaptic neurons in the cat are excited by myelinated nociceptors

Ossipov

et al. 2007

Pain

The dorsal column pathway consists of direct projections from primary afferents and of ascending fibers of the post-synaptic dorsal column (PSDC) cells. This pathway mediates touch but may also mediate allodynia after nerve injury. The role of PSDC neurons in nerve injury-induced mechanical allodynia is unknown. Repetitive gentle, tactile stimulus or noxious pinch was applied to the ipsilateral hindpaw of rats with spinal nerve ligation (SNL) or sham surgery that had previously received tetramethylrhodamine dextran in the ipsilateral n. gracilis. Both touch and noxious stimuli produced marked increases in FOS expression in other cells throughout all laminae of the ipsilateral dorsal horn after nerve injury. However, virtually none of the identified PSDC cells expressed FOS immunofluorescence in response to repetitive touch or pinch in either the nerve-injured or sham groups. In contrast, labeled PSDC cells expressed FOS in response to ureter ligation and labeled spinothalamic tract (STT) cells expressed FOS in response to noxious pinch. Identified PSDC neurons from either sham-operated or SNL rats did not express immunoreactivity to substance P, CGRP, NPY, PKCg, MOR, the NK1 and the NPY-Y1 receptor. Retrogradely labeled DRG cells of nerve injured rats were large diameter neurons, which expressed NPY, but no detectable CGRP or substance P. Spinal nerve injury sensitizes neurons in the spinal dorsal horn to repetitive light touch but PSDC neurons apparently do not participate in touch-evoked allodynia. Sensitization of these non-PSDC neurons may result in activation of projections integral to the spinal/supraspinal processing of enhanced pain states and of descending facilitation, thus priming the central nervous system to interpret tactile stimuli as being aversive.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Nerve injury-induced tactile allodynia is present in the absence of FOS labeling in retrogradely labeled post-synaptic dorsal column neurons

Ossipov

et al. 2007

Pain

The Journal of Physiology

“…2). There are no obvious reasons for this discrepancy; both Angaut-Petit (1975) and Kamogawa & Bennett (1986) used pentobarbitone-anaesthetized preparations and both used a contact thermode to provide the thermal stimulus. Furthermore, the rates of rise and ranges of temperatures employed by Kamogawa & Bennett (1986) are similar to those used in the present experiments.…”

Section: Discussionmentioning

confidence: 99%

Cutaneous excitatory and inhibitory input to neurones of the postsynaptic dorsal column system in the cat.

Noble

Riddell

1988

SUMMARY1. In chloralose-anaesthetized cats single-unit microelectrode recordings were made from axons in the dorsal columns, at the lumbar level, identified as belonging to the postsynaptic dorsal column (PSDC) system.2. Excitatory and inhibitory receptive field arrangements of a sample of seventyfive PSDC neurones were examined in detail using natural cutaneous stimuli.3. The sample was characterized by a high degree of convergent input: 80% of units were activated by both light tactile and noxious mechanical stimuli and more than half of those examined were excited by noxious radiant heat. In addition, threequarters of the units had inhibitory receptive fields on the ipsilateral limb.4. Twenty-three units (27 %) were influenced by input from areas of both hairy and glabrous skin covering the foot and distal limb. Neurones in this group had complex receptive fields, many of which occupied several discontinuous areas of skin. Background and evoked activity of these units could frequently be inhibited by light tactile and/or noxious stimuli. Their inhibitory receptive fields occupied small areas of skin overlapping or adjacent to excitatory fields.5. Fifty-two units (73 %) had receptive fields restricted to areas of hairy skin on the thigh and upper hindlimb. Half the units in this group had coextensive low-and high-threshold excitatory areas but about one-third had a concentric receptive field organization; a high-threshold excitatory component extending beyond, or around, a central low-threshold area. The discharge of these units could be inhibited only by light tactile stimuli. Their inhibitory receptive fields covered extensive areas of skin, sometimes completely surrounding the excitatory field.6. The complex receptive field arrangements observed for neurones of the postsynaptic dorsal column system are discussed in relation to previous observations on dorsal horn neurones of other ascending tracts.

J of Comparative Neurology

“…Cells at the origin of the PSDC pathway in cats commonly carry convergent information from various receptor types, including nociceptive (Angaut- Petit, 1975b;Brown and Fyffe, 1981;Brown et al, 1983;Lu et al, 1983;Kamogawa and Bennett, 1986).…”

Section: Comparative and Functional Considerationsmentioning

confidence: 99%

“…This pathway has relatively recently been recognized as an important source of ascending afferent input to the DCn, along with the more traditionally recognized primary afferent input (Uddenberg, 1966(Uddenberg, , 1968aPetit, 1972;Rustioni, 1973Rustioni, , 1974Rustioni, , 1976Angaut-Petit, 1975a,b;Rustioni and Kaufman, 1977;Rustioni et al, 1979;Brown and Fyffe, 1981;Bennett et al, 1983;Giesler et al, 1984). The PSDC pathway is particularly notable in cats, because a high proportion of recorded spinal cord neurons projecting in the pathway receive nociceptive input (Kamogawa and Bennett, 1986). In contrast, nociceptive input to PSDC cells in rats was not readily demonstrable (Giesler and Cliffer, 1985).…”

mentioning

confidence: 99%

Distribution of the postsynaptic dorsal column projection in the cuneate nucleus of monkeys

Cliffer

Willis

1994

Cells in the spinal cord that are postsynaptic to primary afferent fibers project to the dorsal column nuclei in the postsynaptic dorsal column pathway. The projection of cells in the cervical spinal cord of monkeys to the cuneate nucleus has been reported to avoid pars rotunda of that nucleus, the part that contains the somatotopic representation of the ipsilateral hand. We used the sensitive anterograde tracer Phaseolus vulgaris leucoagglutinin to reexamine this projection. We made multiple iontophoretic injections into the cervical enlargements of three monkeys (two Macaca fascicularis and one Macaca mulatta). Control injections were made in the contralateral dorsal columns of one of these and in the dorsal roots of a fourth animal (M. fascicularis) to test for transport by fibers of passage. After 28-39 days, the animals were deeply anesthetized and perfused, and the tissue was processed for immunohistochemical detection of the label. In all cases (excluding control injections), labeled fibers and varicosities were distributed widely in the ipsilateral cuneate and external cuneate nuclei, including pars rotunda. The dorsal column nuclei ipsilateral to control injections contained no label or only very few poorly labeled fibers, indicating that labeling through fibers of passage did not contribute importantly to the results. This study indicates that the postsynaptic projection to the cuneate nucleus is widespread and includes pars rotunda. Such projections may contribute to transmission of information originating in nociceptors through the dorsal column-medial lemniscal system to the ventrobasal thalamus.