Influence of map scale on primary afferent terminal field geometry in cat dorsal horn

1991 ◽  
Vol 66 (3) ◽  
pp. 696-704 ◽  
Author(s):  
R. J. Millecchia ◽  
L. M. Pubols ◽  
R. V. Sonty ◽  
J. L. Culberson ◽  
W. E. Gladfelter ◽  
...  
Keyword(s):  
Dorsal Horn ◽  
Receptive Fields ◽  
Primary Afferent ◽  
Afferent Terminal ◽  
Absolute Requirement ◽  
Primary Afferent Fibers ◽  
Somatotopic Map ◽  
Field Geometry ◽  
Map Scale ◽  
Primary Afferent Terminal

1. Thirty-one physiologically identified primary afferent fibers were labeled intracellularly with horseradish peroxidase (HRP). 2. A computer analysis was used to determine whether the distribution of cutaneous mechanoreceptive afferent terminals varies as a function of location within the dorsal horn somatotopic map. 3. An analysis of the geometry of the projections of these afferents has shown that 1) terminal arbors have a greater mediolateral width within the region of the foot representation than lateral to it, 2) terminal arbors have larger length-to-width ratios outside the foot representation than within it, and 3) the orientation of terminal arbors near the boundary of the foot representation reflects the angle of the boundary. Previous attribution of mediolateral width variations to primary afferent type are probably in error, although there appear to be genuine variations of longitudinal extent as a function of primary afferent type. 4. Nonuniform terminal distributions represent the first of a three-component process underlying assembly of the monosynaptic portions of cell receptive fields (RFs) and the somatotopic map. The other two components consist of the elaboration of cell dendritic trees and the establishment of selective connections. 5. The variation of primary afferent terminal distributions with map location is not an absolute requirement for development of the map; for example, the RFs of postsynaptic cells could be assembled with the use of a uniform terminal distribution for all afferents, everywhere in the map, as long as cell dendrites penetrate the appropriate portions of the presynaptic neuropil and receive connections only from afferent axons contributing to their RFs.(ABSTRACT TRUNCATED AT 250 WORDS)

Neonatal inflammation and primary afferent terminal plasticity in the rat dorsal horn

Pain ◽  
2003 ◽  
Vol 105 (1) ◽  
pp. 185-195 ◽  
Author(s):  
Suellen M Walker ◽  
Jacqueta Meredith-Middleton ◽  
Claire Cooke-Yarborough ◽  
Maria Fitzgerald
Keyword(s):  
Dorsal Horn ◽  
Primary Afferent ◽  
Afferent Terminal ◽  
Primary Afferent Terminal

Ultrastructural Analysis of Ectopic Synaptic Boutons Arising From Peripherally Regenerated Primary Afferent Fibers

1999 ◽  
Vol 81 (4) ◽  
pp. 1636-1644 ◽  
Author(s):  
H. Richard Koerber ◽  
Karoly Mirnics ◽  
Anahid M. Kavookjian ◽  
Alan R. Light
Keyword(s):  
Dorsal Horn ◽  
Sensory Neurons ◽  
Ultrastructural Analysis ◽  
Peripheral Stimulus ◽  
Primary Sensory Neurons ◽  
Superficial Dorsal Horn ◽  
Primary Afferent ◽  
Afferent Fibers ◽  
Primary Afferent Fibers ◽  
Synaptic Boutons

Ultrastructural analysis of ectopic synaptic boutons arising from peripherally regenerated primary afferent fibers. The central axons of peripherally regenerated Aβ primary sensory neurons were impaled in the dorsal columns of α-chloralose-anesthetized cats 9–12 mo after axotomy. The adequate peripheral stimulus was determined, and the afferent fibers intracellularly stimulated while simultaneously recording the resulting cord dorsum potentials (CDPs). Fibers that successfully had reinnervated the skin responded to light tactile stimulation, and evoked CDPs that suggested dorsally located boutons were stained intracellularly with horseradish peroxidase (HRP). Two HRP-stained regenerated Aβ afferent fibers were recovered that supported large numbers of axon collaterals and swellings in laminae I, IIo, and IIi. Sections containing the ectopic collateral fibers and terminals in the superficial dorsal horn were embedded in plastic. Analyses of serial ultrathin sections revealed that ectopic projections from both regenerated fibers supported numerous synaptic boutons filled with clear round vesicles, a few large dense core vesicles (LDCVs) and several mitochondria (>3). All profiles examined in serial sections (19) formed one to three asymmetric axo-dendritic contacts. Unmyelinated portions of ectopic fibers giving rise to en passant and terminal boutons often contained numerous clear round vesicles. Several boutons (47%) received asymmetric contacts from axon terminals containing pleomorphic vesicles. These results strongly suggest that regenerated Aβ fibers activated by light tactile stimuli support functional connections in the superficial dorsal horn that have distinct ultrastructural features. In addition, the appearance of LDCVs suggests that primary sensory neurons are capable of changing their neurochemical phenotype.

Response and receptive-field properties of spinomesencephalic tract cells in the cat

1986 ◽  
Vol 55 (1) ◽  
pp. 76-96 ◽  
Author(s):  
R. P. Yezierski ◽  
R. H. Schwartz
Keyword(s):  
Spinal Cord ◽  
Receptive Field ◽  
Dynamic Range ◽  
Receptive Fields ◽  
The Body ◽  
Noxious Stimulation ◽  
Primary Afferent ◽  
Receptive Field Properties ◽  
Afferent Fibers ◽  
Primary Afferent Fibers

Recordings were made from 90 identified spinomesencephalic tract (SMT) cells in the lumbosacral spinal cord of cats anesthetized with alpha-chloralose and pentobarbital sodium. Recording sites were located in laminae I-VIII. Antidromic stimulation sites were located in different regions of the rostral and caudal midbrain including the periaqueductal gray, midbrain reticular formation, and the deep layers of the superior colliculus. Twelve SMT cells were antidromically activated from more than one midbrain level or from sites in the medial thalamus. The mean conduction velocity for the population of cells sampled was 45.2 +/- 21.4 m/s. Cells were categorized based on their responses to graded intensities of mechanical stimuli and the location of excitatory and/or inhibitory receptive fields. Four major categories of cells were encountered: wide dynamic range (WDR); high threshold (HT); deep/tap; and nonresponsive. WDR and HT cells had excitatory and/or inhibitory receptive fields restricted to the ipsilateral hindlimb or extending to other parts of the body including the tail, forelimbs, and face. Some cells had long afterdischarges following noxious stimulation, whereas others had high rates of background activity that was depressed by nonnoxious and noxious stimuli. Deep/tap cells received convergent input from muscle, joint, or visceral primary afferent fibers. The placement of mechanical lesions at different rostrocaudal levels of the cervical spinal cord provided information related to the spinal trajectory of SMT axons. Six axons were located contralateral to the recording electrode in the ventrolateral/medial or lateral funiculi while two were located in the ventrolateral funiculus of the ipsilateral spinal cord. Stimulation at sites used to antidromically activate SMT cells resulted in the inhibition of background and evoked responses for 22 of 25 cells tested. Inhibitory effects were observed on responses evoked by low/high intensity cutaneous stimuli and by the activation of joint or muscle primary afferent fibers. Based on the response and receptive-field properties of SMT cells it is suggested that the SMT may have an important role in somatosensory mechanisms, particularly those related to nociception.

The effect of bicuculline on primary afferent terminal excitability

1971 ◽  
Vol 32 (1) ◽  
pp. 261-265 ◽  
Author(s):  
Richard A. Levy ◽  
Allan H. Repkin ◽  
Edmund G. Anderson
Keyword(s):  
Primary Afferent ◽  
Afferent Terminal ◽  
Primary Afferent Terminal ◽  
Terminal Excitability

Structure-function relationships in rat medullary and cervical dorsal horns. II. Medullary dorsal horn cells

1986 ◽  
Vol 55 (6) ◽  
pp. 1187-1201 ◽  
Author(s):  
W. E. Renehan ◽  
M. F. Jacquin ◽  
R. D. Mooney ◽  
R. W. Rhoades
Keyword(s):  
Receptive Field ◽  
Dorsal Horn ◽  
Dynamic Range ◽  
Receptive Fields ◽  
Noxious Stimulation ◽  
Medial Lemniscus ◽  
Guard Hair ◽  
Primary Afferent ◽  
Medullary Dorsal Horn ◽  
Low Threshold

In Nembutal-anesthetized rats, 31 physiologically identified medullary dorsal horn (MDH) cells were labeled with horseradish peroxidase (HRP). Ten responded only to deflection of one or more vibrissae. Six cells were activated by guard hair movement only, six by deflection of guard hairs or vibrissa(e), and seven by pinch of facial skin with serrated forceps. Different classes of low-threshold cells could not be distinguished on the basis of their somadendritic morphologies or laminar distribution. Neurons activated by multiple vibrissae were unique, however, in that one sent its axon into the medial lemniscus, and three projected into the trigeminal spinal tract. None of the guard hair-only or vibrissae-plus-guard hair neurons had such projections. Cells that responded best to noxious stimulation were located mainly in laminae I, II, and deep V, while neurons activated by vibrissa(e) and/or guard hair deflection were located in layers III, IV, and superficial V. Low-threshold neurons generally had fairly thick dendrites with few spines, whereas high-threshold cells tended to have thinner dendrites with numerous spines. Moreover, the dendritic arbors of low-threshold cells were, for the most part, denser than those of the noxious cells. Neurons with mandibular receptive fields were located in the dorsomedial portion of the MDH; cells with ophthalmic fields were found in the ventrolateral MDH, and maxillary cells were interposed. Cells sensitive to deflection of dorsal mystacial vibrissae and/or guard hairs were located ventral to those activated by more ventral hairs. Neurons with rostral receptive fields were found in the rostral MDH, while cells activated by hairs of the caudal mystacial pad, periauricular, and periorbital regions were located in the caudal MDH. Receptive-field types were encountered that have not been reported for trigeminal primary afferent neurons: multiple vibrissae; vibrissae plus guard hairs; and wide dynamic range. The latter two can be explained by the convergence of different primary afferent types onto individual neurons. Our failure to find a significant relationship between dendritic area (in the transverse plane) and the number of vibrissae suggests that primary afferent convergence may not be responsible for the synthesis of the multiple vibrissae receptive field. Excitatory connections between MDH neurons may, therefore, account for multiple vibrissae receptive fields in the MDH.

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