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KMID : 0350519930460041557
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Journal of Catholic Medical College
1993 Volume.46 No. 4 p.1557 ~ p.1569
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Spinal Cord Diffusion Pathway of Tracer Substance Injected into the Epidural Space in Rabbits
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Abstract
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The accurate distribution route of the drugs injected into the epidural space to the spinal cord is yet unknown. The present study was designed to trace such routes after injection of a tracer substance into the epidural space. The injectable
mixture of
tracer substance, 0.5 gm of ferric oxide (iron sesquioxide) mixed with 2 ml of lactated Ringer´s solution, was prepared immediately prior to injection. The 2% jelly solution made from 2.0 gm of commercially available vegetable jelly powder
dissolved in
100 ml of boiled lactated Ringer´s solution was filtered with microfilter(epidural flat filter) and bottled. And autoclaved. We divided 10 adult rabbits randomly into 2 groups of 5. The animals were anesthetized by intraperitoneal instillation of
20%
urethene, 7 ml/kg body weight.
Each of the aminals in the tracer substance injected group(T group) was slowly injected of 1.5 ml of the mixture of tracer substance through a 19 G pediatric epidural needle at the T5-6 interspace in the sphinx position, and observed for 40
minutes
subsequantly. On the other hand, the ielly solution pretreated group(J group) was slowly injected of 1.2 ml of jelly sloution epidurally, and 15 minutes later 1.2 ml of the mixture was injected, and observed for 40 minutes.
During the observation we noted in both groups fine, irregular contractions in a part of the trapezius muscle that originated from the supraspinous ligament of T 3, 4 and 5 vertebrae. The irregular contraction of muscle developed about 12 minutes
after
the injection of the tracer mixture and continued throughout the experimentation.
After 40 minutes of ooseration animals were killed by shedding blood, and a segment of the bodies of the 1st through 8th thoracic vertebrae was removed and fixed in 10% formalin solution. Following decalcification with 50% formic acid
histological
study
of vertebrae, epidural structures and the spinal cord was performed with hematoxylin-eosin(H-E) stain in transverse sections.
@ES The results were as follows :
@EN 1. Epidurally administered tracer substance were diffused through the extracellular matrix of hyaline cartilage and the bone marrow of upper thoracic vertebrae. There was evidence of sbsorption of the tracer substance unrestrictedly into
venous
sinuses of the bone marrow.
2. In the epidural space, most of the tracer substance was dispersed through the ground substance and along the connective tissue of the arterial wall to other tissues.
3. The perivascular spaces of the pia mater and the peripheral areas of the white matter are connected with the extracellular space of the spinal cord.
4. The extracellular space of the spinal cord is extended from the epispinal space, glia limitans, processes of astrocytes and oligodendrocytes, and perivascular end-feet to the extracellular space of the gray matter and finally interlinked with
the
central canal.
5. The tracer substance passages between astrocytes and oligodendrocytes in the white matter specimen demonstrated a typical syncytium of the glial cells of CNS.
6. The distribution on tracer substance in the jelly-solution pretreated group was scanty in the dura mater and epidural space, and prominent in the epidural arterial vascular walls and the spinal extracellular space. These findings suggest
differences
in the flow rate of extracellular fluid in the intraspinal structures.
These results indicate that the epidurally administered tracer substance is routed to the epidural vascular walls, the spinal extracellular space, and finally to the central canal. In addition, from the results of the time-lag injection study of
2%
jelly solution and tracer mixture into the epidural space, it is inferred that the flow of extracellular fluid both in the epidural arterial walls and the spinal extracellular space is relatively fast, whereas it is slow or stagnant in the
duramater and
epidural space.
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