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Journal of the Anatomical Society of India

A Golgi Study of Nucleus Proprius In Rat Lumbar Dorsal Spinal Horn

Author(s): Bhardwaj R., Nagar M. and Prakash R.

Vol. 53, No. 2 (2004-07 - 2004-12)

University College Of Medical Sciences, Shahdara, Delhi.

Abstract:

The dorsal gray matter plays an important role in various sensory modalities. Most of the work has been conducted on the superficial dorsal gray matter, the substantia gelatinosa, but literature available on the cytoarchitecture of the deeper zones of gray matter is scarce. The present work is an attempt to study the neuronal population in the nucleus proprius using Golgi technique in the lumbar spinal cord.

Fifteen adult Wistar rats of either sex were taken. The spinal cord was dissected out and processed for light microscopy for Golgi study using Fox's Golgi Cox method.Dendritic branching pattern of the neurons in the nucleus proprius was observed. The nucleus proprius was found to be divisible into a dorsal and a ventral divisions. The dorsal division showed closely packed smaller neurons whereas cells in the ventral division were large and loosely packed.On the basis of their shape and processes,neurons could be classified into islet and stalked cells.The islet cells are more commonly observed in the dorsal division.These cells are small with a fusiform or spindle shaped body having two or three dendrites.The dendritic extent appears to be restricted to a narrow band of gray matter.The stalked cells are larger cells ,more commonly observed in the ventral division having a round or polygonal soma giving rise to three or more dendrites.The dendritic extent appears to be greater than that of islet cells.

Key words: nucleus proprius, spinal dorsal horn.

Introduction:

The role of dorsal gray horn in various sensory modalities including nociception is well documented. Rolando (1824), first identified the gelatinous substance in the dorsal gray horn and divided it into an outer, thin zone, containing large neurons called the marginal zone of Waldeyer and a deeper part made up of smaller neurons called the substantia gelatinosa. Ventral to the substantia gelatinosa, another nuclear group, the dorsal funicular group, was first mentioned by Waldeyer (1888),which was later named as the nucleus proprius . The literature reveals that the description of the dorsal spinal gray lamination is conflicting and mostly on neonatal, young and adult cats, which has been applied de facto to other mammals. The superficial dorsal gray matter has been widely studied, but literature is scarce on the zone deeper to the substantia gelatinosa, the nucleus proprius.In our previous work, we have done detailed analysis of histomorphometry of nucleus proprius using Cresyl fast-violet staining Bhardwaj et al (2001).The present work is an attempt to study the different types of neuronal population with emphasis on the branching pattern of their processes using Golgi technique.

Material and Methods:

Fifteen adult Wistar rats (200-250 gms.) were anesthetized and perfused. Spinal cord was dissected out and lumbar portion of the spinal cord processed for light microscopy for Golgi study using Fox's Golgi Cox technique. Free hand (90-100 um thick) sections were cut and viewed under the light microscope and photographed.

Observations:

The dorsal horn appears to be capped with a crescentric neuronal zone, the substantia gelatinosa, recognized by the presence of densely packed small neurons.Ventral to the substantia gelatinosa, is a group of cells, the nucleus proprius,which contains less densely packed neurons. No strict boundaries could be appreciated between these two zones,hence an arbitrary depth of 100µm from the dorsal surface of spinal cord, Todd and Lewis (1986), was taken as a guide to delineate the boundary between the two zones. In cross section, the nucleus proprius appeared to be an oval shaped area with a convexity towards substantia gelatinosa. It has a densely cellular zone dorsally and a cell-poor zone ventrally.The dorsal zone extending 100µm dorsoventrally was named as the dorsal division. The cell-poor zone, called the ventral division, could be differentiated from the subjacent deeper area by the reticular appearance which characterizes the latter, Bhardwaj et al (2001). The dorsoventral width of this zone was 200 µm.

Fox's Golgi cox method was employed to study the dendritic branching pattern of neurons in the dorsal and ventral divisions of nucleus proprius. With this technique, the neurons were stained at random and the apparent size of the cells appears to be larger than its actual size because of deposition of silver salts. On the basis of their dendritic branching pattern, the neurons were classified into two major types, islet cells and stalked cells.

Islet cells were predominant cell type in the dorsal division of nucleus proprius. A typical islet cell showed a fusiform or spindle shaped cell body giving rise to two or three dendrites (Fig 1.). A recurrent pattern of branching was observed in the dendrites, often restricted to a narrow band within the dorsal division.

Stalked cells,larger than islet cells, were predominant in the ventral division showing a rounded or polygonal soma giving rise to three or four primary dendrites which spread dorso- ventrally and mediolaterally (Fig 2.). Secondary branches arise form the primary dendrites after a short distance away from the soma. Considering the thickness of the dendrites, it appeared that the dendritic spread of these cells is greater compared to the islet cells.

Fig. 1:

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Fox's Golgi-cox preparation showing an islet cell (I) in the dorsal division of nucleus proprius of lumbar spinal dorsal horn.

Fig. 2:

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Fox's Golgi-cox preparation showing a stalked cell (S) in the ventral division of nucleus proprius of lumbar spinal dorsal horn.

Discussion:

Transversely cut, 90-100m thick sections of spinal cord were stained with Fox's Golgi-Cox method, which revealed two types of neurons in the dorsal and ventral divisions of nucleus proprius.

Islet cells were more commonly observed in the dorsal division of nucleus proprius. These cells are characterized by a spindle or fusiform cell body giving rise to two or three dendrites which show recurrent pattern of branching. The dendritic extent appears to be restricted to a narrow band of gray matter within the dorsal horn. These findings could be compared to those of Matsushita (1969) and Mannen and Suguira (1976). In their Golgi studies on spinal cord of kitten, they described similar neurons in lamina III of dorsal horn, having a fusiform or spindle shaped cell body. The dendritic ramifications of these neurons were observed to be limited within the lamina. Beal and Cooper (1978) also described similar type of cells in laminae II and III of spinal dorsal horn of monkey, while Todd and Lewis (1986) revealed the presence of islet cells in lamina II (substantia gelatinosa) of rat spinal dorsal horn.

Stalked cells represented the second cell type. These larger cells were commonly seen in the deeper part of nucleus proprius i.e., the ventral division. They are characterized by rounded or polygonal soma giving rise to three or four primary dendrites. Secondary branches arise from a short distance away from the soma. Their dendritic extent appears to be greater than that of islet cells. Similar stalked cells were observed by Beal and Cooper (1978) in lamina IV of spinal dorsal horn in his study on macaque monkey. Todd and Lewis (1986) revealed the presence of islet and stalked cells in the substantia gelatinosa (lamina II) of spinal dorsal horn.

The present work revealed that the observations recorded in the dorsal and ventral divisions of nucleus proprius were comparable to the findings observed in lamina III and lamina IV, respectively, by other workers in different mammals.The nucleus proprius was confined to lamina III and lamina IV and could be distinguished from areas of gray matter lying dorsal and ventral to it ie lamina II and laminaV respectively, Bhardwaj et al (2001).

References:

  1. Beal J. A. and Cooper M.H. The neurons in the gelatinosal complex (laminae II and III) of the monkey (Macaca mulatta); a Golgi study. Journal of Comparative Neurology.1978; 179: 89-122.
  2. Mannen H. and Suguira Y. Reconstruction of neurons of dorsal horn proper using Golgi stained serial sections. Journal of Comparative Neurology.1976; 168 : 303-312.
  3. Matsushita M. Some aspects of the interneuronal connections in cat's spinal gray matter. Journal of Comparative Neurology.1969; 136 : 57-80.
  4. Rolando L. Ricerche anatomiche sulla struttura del midollo spinale. Torino. Quoted by Beal J. A., and Cooper M.H. (1978).
  5. Todd A.J. and Lewis S. G.The morphology of Golgi-stained neurons in lamina II of the rat spinal cord. Journal of Anatomy .1986; 149 : 113-119.
  6. Waldeyer H. (1888): Das Gorilla - Ruckenmarck. Abhandl. J. Kaiserl. Akad. d. wissensch zu Berlin. Quoted by Beal J.A. and Cooper M. H. (1978).
  7. Bhardwaj R.,Nagar M. and Prakash R. Histomorphometry of nucleus proprius in rat lumbar dorsal spinal horn.Journal of the Anatomical Society of India.2001; 50(2) :140-144. J.Anat. Soc. India 53 (2) 61-62 (2004)
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