Ultrastructural changes of synaptic glomeruli following intrathecal injection of distilled water to rats

We attempted to identify synaptic glomeruli in the spinal substantia gelatinosa of rats by injecting distilled water into the subarachnoid space. The altered synaptic glomeruli were visualized when injecting 1.0 ml of distilled water, though the incidence of degenerative synaptic glomeruli was rare in the case of an injection of 0.5 ml or less. We assume that when the distilled water is injected, there is a sudden change in homeostatic balance in cerebrospinal fluid, following inhibition of nerve impulses in the dorsal root and the altered synaptic glomeruli. Ultrastructurally, the injection of distilled water led to a preferential degeneration of synaptic glomeruli derived from the C-fibers.