Richard T. Stevens

Direct spinal projections to limbic and striatal areas: Anterograde transport studies from the upper cervical spinal cord and the cervical enlargement in squirrel monkey and rat

With the anterograde tracers Phaseolus vulgaris‐leucoagglutinin (PHA‐L) and biotinylated dextranamine (BD), direct spinal connections from the upper cervical spinal cord (UC; C1 and C2) and the cervical enlargement (CE; C5‐T1) were demonstrated in various striatal and limbic nuclei in both squirrel monkey and rat. Within each species and from each spinal level, the total number of terminals seen in the limbic and striatal areas was approximately 50–80% of the number seen within the thalamus. Labeled terminal structures were seen in the hypothalamic nuclei, ventral striatum, globus pallidus, amygdala, preoptic area, and septal nuclei. In both species, the number of labeled terminals in limbic and striatal regions was larger from UC than from CE, although the distributions to each nucleus varied with the specific lamina injected. In both species and from both UC and CE, approximately one‐half of the projections to striatal and limbic areas terminated in the hypothalamus. The only region that demonstrated a topographical organization was the globus pallidus, where terminals from the CE were located dorsomedially to those from the UC. In the rat, UC and CE injections into the lateral dorsal horn and pericentral laminae resulted in the largest number of limbic and striatal terminations. The proportion of ipsilateral terminations was greatest when the medial laminae in the UC or the lateral dorsal horn in the CE received injections.

Spinothalamocortical projections to the secondary somatosensory cortex (SII) in squirrel monkey

Anterograde labeling of the cervical spinothalamic tract was combined with retrograde labeling of thalamocortical cells projecting to the hand region of the second somatosensory cortex (hSII) to identify likely sites in the thalamus for processing and transmitting nociceptive information to hSII. Anterograde labeling of terminals was done with 2% WGA-HRP injections in the cervical enlargement; thalamocortical cells were retrogradely labeled with fluorescent tracers. In one experiment, the contralateral primary somatosensory cortex hand region (hSI) was injected to provide a direct comparison with hSII thalamic label. Both labeled cells and terminal-like structures were visualized in single thalamic sections and their numbers and positions quantitatively analyzed. The number of labeled cells within 100 microns from the STT terminals were counted as overlapping cells. Four thalamic nuclei, ventroposterior inferior (VPI), ventroposterior lateral (VPL), posterior nucleus (PO) and centrolateral nucleus (CL) combined to contain 86.5% of all hSII-projecting overlapping cells. Of all hSII-projecting thalamic overlapping cells, VPI contained the largest number (36.4% of the total) followed by the anterior portion of the posterior nuclear complex (POa; 20.4%), VPL (18.3%) and CL (11.4%). Results of the hSI injection show a different pattern of overlap in agreement with our earlier study. The relative distribution of overlapping cells was dependent on the antero-posterior position of the SII injections. The most anterior injections resulted in small numbers of labeled cells, with the majority of overlapping cells located in PO and CL. The more posterior injections resulted in overlapping cells mainly in VPI and VPL.(ABSTRACT TRUNCATED AT 250 WORDS)

Ko¨lliker-Fuse nucleus: the principal source of pontine catecholaminergic cells projecting to the lumbar spinal cord of cat

Abstract Using retrograde transport of the fluorescent dye Evans Blue (EB), in combination with glyoxylic acid histofluorescence, the ponto-spinal catecholaminergic pathways were investigated. The cells which contain catecholamine and project to the lumbar spinal cord of the cat are most densely concentrated in the Ko¨lliker-Fuse nucleus. Locus coeruleus, the subcoeruleus area, and the parabrachial nuclei were found to have relatively few cells that both contain catecholamine and project to the lumbar spinal cord.

A dorsolateral spinothalamic pathway in cat

A spinothalamic tract that courses in the dorsolateral funiculus of the spinal cord and originates almost exclusively from spinal lamina I neurons has been demonstrated in the cat by retrograde transport of horseradish peroxidase. This tract is of special interest because the course of this predominantly lamina I, contralateral projection lies outside the classical course of the spinothalamic tract and because most lamina I cells contributing to the spinothalamic tract have been shown by other investigators to respond exclusively to somatic noxious stimuli. This newly described tract has important implications in the processing of noxious stimuli.

Funicular course of catecholamine fibers innervating the lumbar spinal cord of the cat

The purpose of this study was to determine the funicular location of descending catecholamine (CA) fibers innervating the lumbar spinal cord from the dorsolateral pons (DLP). The locations of catecholamine-containing cell bodies which project to the lumbar spinal cord were determined by combining the use of the retrogradely transported fluorescent dye, Evans Blue (EB), with the glyoxylic acid histofluorescence technique. Lumbar injections of Evans Blue were combined with thoracic lesions of the dorsolateral funiculi (DLF) or ventrolateral funiculi (VLF) in order to retrogradely label those CA-containing or non CA-containing cell bodies whose axons descend within the spared hemispinal cord. By this technique it was determined that descending CA fibers innervating the lumbar spinal cord of the cat project through both the DLF and the VLF. The nucleus subcoeruleus, the Kolliker-Fuse nucleus and the CA cell bodies in the area of A5 each contain a significant number of CA-containing cells whose fibers descend both within the DLF and the VLF, while the nucleus locus coeruleus projects to the lumbar cord primarily through the VLF. Catecholamine cells of the DLP innervate the lumbar spinal cord bilaterally, although there is an ipsilateral predominance. The CA-containing cells of the DLP which innervate the contralateral spinal cord were shown by ipsilateral or contralateral thoracic hemisection to decussate both above and below the thoracic lesion. Non-CA-containing cells from the DLP also crossed at all levels of the spinal cord; however, cells from the caudal pons had a larger number of cells which crossed above the thoracic lesion while cells of the more rostral pons had a larger number of cells which crossed below the lesion.

Medial, Intralaminar, and Lateral Terminations of Lumbar Spinothalamic Tract Neurons: A Fluorescent Double-Label Study

A dorsolateral spinothalamic tract (DSTT), consisting primarily of lamina I neurons, was confirmed in the cat lumbar spinal cord by the use of thalamic injections of fluorescent dyes combined with selective thoracic spinal cord lesions. In addition, collateralization of spinothalamic tract (STT) terminations to medial, lateral, and intralaminar thalamic regions was investigated by injections of two different fluorescent dyes into pairs of these regions. The results of this study indicate that less than 15% of cat lumbar STT neurons collateralize to more than one of the thalamic regions evaluated. Lumbar lamina I cells project to the lateral and to the medial thalamus (13% collateralize to these two regions) and have only a scant projection to the intralaminar thalamus. Lumbar laminae IV-VI STT cells are very few in cat and demonstrate almost no collateralization to multiple thalamic areas. Neurons of laminae VII-X project equally to the three thalamic regions evaluated, and approximately 10-14% of cells from this laminar group collateralize to any two of the thalamic sites evaluated.

Funicular location of ascending axons of lamina I cells in the cat spinal cord

The laminar distribution of spinal cord neurons projecting suprasegmentally through different funiculi was determined in the cat using horseradish peroxidase (HRP) injections combined with selective spinal cord lesions. The lesions were designed to limit the caudal transport of HRP to either the ventral funiculi or the dorsolateral funiculus. HRP injections in the ventromedial or ventrolateral funiculi resulted in labeling primarily within laminae IV-VIII and a virtual lack of labeling within lamina I. When the dorsolateral funiculus was injected, 20-25% of all labeled cells were located in lamina I, bilaterally. These results demonstrate that the ascending lamina I projections are through the dorsolateral funiculus.

Identification of functioning cortex using cortical optical imaging.

OBJECTIVE The purpose of this study was to evaluate the technique of cortical optical imaging (COI) of intrinsic cortical optical signals related to neuronal activation. The specific goals of the study were to evaluate some of the technical aspects of COI and thus maximize the intensity of the image of this intrinsic signaling process and to determine the physiological reliability of COI in a well-defined animal system. METHODS The intrinsic optical signal of activated whisker barrel cortex of rat was imaged using a computer-based technique for rapid acquisition of enhanced images. Single-unit microelectrode recordings of cortical neuronal responses to whisker movement were used to confirm the locations of the whisker barrels. RESULTS Narrow band incident light at 600- to 610-nm wavelength was most effective for producing optical images. Images could be obtained during activation by a single long (40 s) stimulus or by averaging the signal generated by repeated shorter (1-8 s) stimuli. Focusing slightly below the cortical surface, minimizing movement, and abolishing extraneous light were all important in increasing the signal-to-noise ratio. The locations of whisker movement-evoked cortical activity determined using COI are consistent with the known functional anatomy of rat whisker barrel cortex. The images obtained with this experimental arrangement are shown to be accurate predictors of the location of neuronal activity determined by comparing the locations of active sites identified with COI with locations of areas of neuronal activity determined using single-cell recording techniques. CONCLUSIONS COI is able to rapidly identify areas of cortex containing elicited neuronal activity. The technique allows cortical activation maps to be made rapidly with a very high degree of spatial resolution. COI is reliable and consistent over time. COI, if used carefully, holds promise as an intraoperative technique to study both human and experimental animal cortical function.

Spinothalamocortical inputs nonpreferentially innervate the superficial and deep cortical layers of SI

Using a combined anterograde and retrograde tracing technique, we examined the distribution pattern of the thalamocortical cells which projected to superficial layers of the hand region of the primary somatosensory cortex (hSI), and quantitatively analyzed the retrogradely labeled cells which putatively contacted terminals of the spinothalamic tract (STT) in the squirrel monkey and the macaque. Less than 25% of the superficial hSI projecting cells were putatively contacted by terminals of cervical enlargement spinothalamic neurons. These cells were primarily located in ventroposterior lateral, ventroposterior inferior and centrolateral nuclei. Although the number of superficial hSI projecting cells numbered less than 20% of the total hSI projecting cells, their patterns of location and their proportion of overlap with STT terminals within each thalamic nucleus were similar. It is suggested that the spinothalamic nociceptive information input to to the cortex equally accesses both superficial and deep SI.

Catecholamine varicosities in cat dorsal root ganglion and spinal ventral roots

Abstract Catecholamine (CA) varicosities have been observed within the dorsal root ganglion and spinal ventral roots of the cat at all spinal levels. There was no apparent change in either appearance or numbers of these CA varicosities following spinal transection or distal spinal root lesion. It is suggested that the source of CA innervation of these areas is sympathetic accompanying transdural blood vessels.