Gray commissure

About: Gray commissure is a research topic. Over the lifetime, 40 publications have been published within this topic receiving 3224 citations.

A modified peroxidase--antiperoxidase procedure for improved localization of tissue antigens: localization of substance P in rat spinal cord.

Abstract: A procedure is presented which modifies the Sternberger peroxidase--antiperoxidase (PAP) technique in order to visualize additional amounts of immunodeposits representing the antigen substance (SP) in 5-micrometer paraffin tissue sections of rat spinal cord. For increased sensitivity, the new procedure utilizes a "double bridge" and diaminobenzidine in low pH buffer. The modifications have made possible the visualization of immunoreactive beaded processes and punctate bodies, which were then traced to determine patterns of SP circuitry. Using the modified PAP procedure, the greatest number of immunoreactive processes appeared in the dorsal horn, where some punctate bodies and varicose processes could be seen adjacent to the myelinated afferent fiber bundles that penetrate the substantia gelatinosa as dorsal root collaterals. Additional immunoreactive processes and punctate bodies coursed through the myelinated afferent fiber bundles that penetrate the dorsolateral white matter, and extend into the intermediolateral gray region. Substance P was also identified within immunoreactive processes found in Rexed's laminae V and VI, as well as the central canal region, the dorsal gray commissure, and the ventral gray and white commissures. Since the modifications improved the visualization of SP-containing processes in sparsely populated regions of the spinal cord, especially the ventral horn, they may be useful in demonstrating other antigens that normally occur in small quantities within tissues.

Parasympathetic preganglionic neurons and visceral primary afferents in monkey sacral spinal cord revealed following application of horseradish peroxidase to pelvic nerve.

Abstract: Horseradish peroxidase (HRP) applied to the central stump of the transected pelvic nerve of rhesus monkeys labeled afferent and efferent neurons innervating the pelvic viscera. Preganglionic neurons forming the sacral parasympathetic nucleus (SPN) were located in a narrow band 150–200 μm wide on the border of the ipsilateral intermediate gray matter. The SPN contained an average of 820 neurons and characteristically extended over two or three sacral segments (average length: 14.5 mm) with the majority of cells in S2. It was composed of medium sized, elongated somata (15.7 × 30.7 μm) with their major axes in the transverse plane and oriented parallel to the lateral border of the gray matter. Dendrites extended deep into the lateral funiculus, horizontally into the medial dorsal gray commissure, and dorso-laterally along the lateral edge of the dorsal horn. Preganglionic axons followed the lateral border of the ventral horn to the ventral rootlets. Pelvic nerve afferent axons carried HRP to neurons in the dorsal root ganglia (DRG) and by transganglionic transport to the spinal cord. The average number of labeled DRG cells was 2, 992 (range: 2, 193–4, 363) with the largest fraction (80%) in S2. The numbers of DRG cells correlated with the numbers of SPN cells in corresponding spinal cord segments. Within the spinal cord labeled primary afferent fibers were prominent in the sacral segments and were also observed in decreasing numbers within two to three segments beyond the rostral and caudal limits of the SPN. In transverse sections, primary afferents were found throughout Lissauer's tract (LT) and in the lateral half of the dorsal columns. A prominent collateral fiber bundle from LT was located in lamina I along the lateral edge of the dorsal horn. This bundle extended into the SPN and a few collaterals continued medially into the dorsal gray commissure and the contralateral side of the cord. A much less prominent collateral fiber group from LT passed medially over the apex of the dorsal horn in lamina 1 and descended into the dorsal gray commissure. Horizontal sections revealed that these two collateral pathways were organized into periodically spaced bundles of fibers about 250 μm apart. HRP reaction product in terminal fields related to these afferent collateral projections were found in the lateral marginal zone and bilaterally in the dorsal gray commissure.

Central projections of afferent renal fibers in the rat: an anterograde transport study of horseradish peroxidase.

Abstract: The projections of afferent renal fibers (ARN) to dorsal root ganglia and into the spinal cord of the rat were studied using the anterograde transport of horseradish peroxidase (HRP). Crystalline HRP was applied to the proximal cut ends of renal nerves or injected as a concentrated solution into the kidney, on either the right or left side. After a survival time of 40–120 h, sections of thoraco-lumbar dorsal root ganglia (DRG) and spinal cord were cut and processed according to the tetramethyl benzidine method. HRP applied either to the ARN or to the kidney on the left labeled neurons in the DRG from T8 to L2. On the other hand, HRP application on the right side resulted in labeling of neurons in DRG T6 to T13. No labeled neurons were found in the contralateral DRG. Labeled neurons in the DRG were of the small (11–20 μm) and medium (30–42 μm) size and were distributed in all portions of the DRG. In the spinal cord the greatest concentration of labeled ARN from the left were found in segments T10-L1, whereas projections from the right ARN were concentrated primarily in segments T7-T10. Labeled fibers entered along the medial aspect of the ipsilateral dorsal horn and projected both rostrally and caudally in the medial portion of Lissauer's tract, sending some collaterals into lamina I. The majority of labeled fibers coursed ventrally along the medial aspect of the dorsal horn towards the midline where they terminated in the region of the dorsal gray commissure, just dorsal to the central canal. Additionally, labeled fibers from the medial projection passed into laminae III-V. No labeled fibers or terminals were observed in the contralateral spinal cord. These data show that ARN enter the spinal cord through several DRG and provide the first anatomical demonstration of central sites of termination of ARN. These spinal sites of projection of sensory information from the kidney are likely to be central sites of integration of reno-renal and visceral reflexes.