scholarly journals Comparative Electron Microscopy of Synapses in the Vertebrate Spinal Cord

1966 ◽  
Vol 1 (1) ◽  
pp. 67-80
Author(s):  
B. T. CHARLTON ◽  
E. G. GRAY
Keyword(s):  
Electron Microscopy ◽  
Spinal Cord ◽  
Synaptic Transmission ◽  
Tight Junctions ◽  
Presynaptic Inhibition ◽  
Grey Matter ◽  
Rare Occurrence ◽  
Lower Vertebrates ◽  
Mode Of Transmission ◽  
Comparative Electron

Synapses with a cleft with ‘thickened’ membranes and presynaptic vesicles and mitochondria occur commonly throughout the grey matter of the spinal cord of goldfish, frog and various mammals studied. Such synapses are generally thought to have a chemical mode of transmission. The absence or rare occurrence of presynaptic neurofilaments in fish and frog accounts for the failure to detect boutons by silver methods, and there is no need to postulate morphologically unspecialized synaptic contacts in the lower vertebrates as some light microscopists did. Both fish and frog show axo-somatic or axo-dendritic tight junctions, which could be sites of electrical synaptic transmission. No neuronal tight junctions have yet been seen in the mammalian spinal cord. Axo-axo-dendritic synapses have been seen in the frog and mammalian cord, but not so far in the fish. Such serial synapses may be responsible for presynaptic inhibition. Neuroglia of fish, frog and mammals have tight junctions at their apposed surfaces. These differ structurally from neuronal tight junctions. Neuroglia in fish cord have, in addition, desmosomes at their apposed surfaces.

Effects of NH4+ on reflexes in cat spinal cord

1990 ◽  
Vol 64 (2) ◽  
pp. 565-574 ◽  
Author(s):  
W. Raabe
Keyword(s):  
Spinal Cord ◽  
Synaptic Transmission ◽  
Nerve Stimulation ◽  
Action Potentials ◽  
Presynaptic Inhibition ◽  
Excitatory Synaptic Transmission ◽  
P Wave ◽  
Postsynaptic Inhibition ◽  
Presynaptic Terminals ◽  
Muscle Nerve

1. In deeply barbiturate-anesthetized animals. NH4+ decreases spinal excitatory synaptic transmission by neuronal depolarization and subsequent block of conduction of action potentials into presynaptic terminals of low-threshold (presumably Ia-) afferents. Because barbiturates by themselves depress excitatory synaptic transmission and may have modified the effects of NH4+, this study examines the effect of NH4+ on excitatory synaptic transmission in the unanesthetized animal. 2. The effects of NH4+ on monosynaptic and polysynaptic excitatory reflexes as well as di- and polysynaptic inhibition were investigated in the spinal cord of the decerebrate and unanesthetized cat in vivo. 3. The monosynaptic excitatory reflex (MSR) elicited by muscle nerve stimulation and polysynaptic excitatory reflexes elicited by muscle (MSR-PSR) or cutaneous nerve stimulation (Cut-PSR) were recorded from the ventral roots L7 or S1. The P-wave was recorded from the cord dorsum. Di- and polysynaptic inhibition was elicited by muscle nerve stimulation and measured as decrease of the MSR. 4. Intravenous infusion of ammonium acetate (AA) decreased MSR and the monosynaptic motoneuron pool excitatory postsynaptic potential (EPSP) recorded from the ventral root (VR-EPSP). Decrease of MSR and VR-EPSP was accompanied by an increase of the intraspinal conduction time in presynaptic terminals. The maximal decrease of the MSR was preceded by a period of transient increase of the MSR and reflex discharges from previously subthreshold VR-EPSPs. 5. The effects of NH4+ on MSR and VR-EPSP are consistent with those in barbiturate-anesthetized animals and suggest that NH4+ also decreases monosynaptic excitation in unanesthetized animals by depolarization and subsequent conduction block for action potentials in presynaptic terminals. 6. Decrease of the MSR was accompanied by a decrease of the P-wave, indicating that NH4+ simultaneously decreases mono- and oligosynaptic excitatory synaptic transmission as well as presynaptic inhibition. 7. Decrease of the MSR was accompanied by increases of MSR-PSR and Cut-PSR and decreases of di- and polysynaptic postsynaptic inhibition. 8. The neuronal circuits underlying MSR-PSR and Cut-PSR include presynaptic inhibition of group I and II afferents as well as postsynaptic inhibition of motoneurons. It is suggested that increases of MSR-PSR and Cut-PSR are contributed to by decreases of pre- and postsynaptic inhibition and neuronal depolarization by NH4+. These effects increase afferent input to motoneurons, permit uncontrolled discharge of motoneurons, and initiate reflex discharges by previously subthreshold excitatory postsynaptic potentials.

Subacute posttraumatic ascending myelopathy in a 15-year-old boy

2014 ◽  
Vol 21 (3) ◽  
pp. 454-457 ◽  
Author(s):  
Timothy J. Kovanda ◽  
Eric M. Horn
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Rare Event ◽  
Fracture Dislocation ◽  
Secondary Injury ◽  
Spinal Cord Trauma ◽  
Rare Occurrence ◽  
Time Period ◽  
Cord Injury ◽  
Complete Spinal Cord Injury

Secondary injury following initial spinal cord trauma is uncommon and frequently attributed to mismanagement of an unprotected cord in the acute time period after injury. Subacute posttraumatic ascending myelopathy (SPAM) is a rare occurrence in the days to weeks following an initial spinal cord injury that is unrelated to manipulation of an unprotected cord and involves 4 or more vertebral levels above the original injury. The authors present a case of SPAM occurring in a 15-year-old boy who sustained a T3–4 fracture-dislocation resulting in a complete spinal cord injury, and they highlight the imaging findings and optimum treatment for this rare event.

Spinal cord grey matter lesions in multiple sclerosis detected by post-mortem high field MR imaging

2008 ◽  
Vol 15 (2) ◽  
pp. 180-188 ◽  
Author(s):  
CP Gilmore ◽  
JJG Geurts ◽  
N Evangelou ◽  
JCJ Bot ◽  
RA van Schijndel ◽  
...  
Keyword(s):  
Spinal Cord ◽  
White Matter ◽  
Mr Imaging ◽  
High Field ◽  
Grey Matter ◽  
Great Majority ◽  
Proton Density ◽  
Post Mortem ◽  
Mr Images ◽  
The Brain

Background Post-mortem studies demonstrate extensive grey matter demyelination in MS, both in the brain and in the spinal cord. However the clinical significance of these plaques is unclear, largely because they are grossly underestimated by MR imaging at conventional field strengths. Indeed post-mortem MR studies suggest the great majority of lesions in the cerebral cortex go undetected, even when performed at high field. Similar studies have not been performed using post-mortem spinal cord material. Aim To assess the sensitivity of high field post-mortem MRI for detecting grey matter lesions in the spinal cord in MS. Methods Autopsy material was obtained from 11 MS cases and 2 controls. Proton Density-weighted images of this formalin-fixed material were acquired at 4.7Tesla before the tissue was sectioned and stained for Myelin Basic Protein. Both the tissue sections and the MR images were scored for grey matter and white matter plaques, with the readers of the MR images being blinded to the histopathology results. Results Our results indicate that post-mortem imaging at 4.7Tesla is highly sensitive for cord lesions, detecting 87% of white matter lesions and 73% of grey matter lesions. The MR changes were highly specific for demyelination, with all lesions scored on MRI corresponding to areas of demyelination. Conclusion Our work suggests that spinal cord grey matter lesions may be detected on MRI more readily than GM lesions in the brain, making the cord a promising site to study the functional consequences of grey matter demyelination in MS.

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