Function and structure in the chronically isolated lumbo‐sacral spinal cord of the dog

Abstract

Could a portion of the spinal cord be isolated by cutting the pathways of incoming nerve impulses and the animal be kept alive, the following questions might be answered: First, is such functionally isolated nervous tissue capable of surviving and what structural alterations does it undergo ? Second, does the isolated nervous tissue exhibit activity; 5s the spinal cord autochthonous? Third, is the so-called trophic control of non-nervous tissues by the nervous system exercised by physical integrity of the nervous tissue, by virtue of some nutritional relationship, or does it derive from activity nervously initiated. This last question may be answered only if the nervous tissue survives but is inactive.If the anterior spinal roots are entirely efferent, the isolation of a length of spinal cord together with its efferent nerve fibers is possible. Six-week-old puppies, litter mates, were used for the attempt. I n a one-stage operation under ether anaesthesia the lumbar and sacral dorsal roots were cut intradurally on both sides and the cord transected above and below. Autopsy showed that the upper transection fell between the last thoracic and first lumbar se,ments in each case, and the lower transection in the last sacral segment in the first two animals and in the mid-sacral region in the third. 109

Differentiation of fast and slow muscles in the cat hind limb

“…As with adult animals (Tower, 1937a(Tower, , b, 1939Eccles, 1941), there has apparently been an absence of all discharge of impulses from the motoneurones. Under such circumstances it was remarkable that the muscles developed so well in size and in power of contraction.…”

Afferent Input Modulates Neurotrophins and Synaptic Plasticity in the Spinal Cord

“…The SI procedures (Fig. 1A) are a modification of the original protocols of Tower (1937), and these procedures have been used routinely in our laboratory . Briefly, the rats were anesthetized with ketamine hydrochloride (100 mg/kg) and xylazine (8 mg/kg) administered intraperitoneally.…”

Interneurones and rigidity of spinal origin

“…Section of dorsal roots, denervating to some degree motoneurones, as well as interneurones, also leads to supersensitivity but not to spontaneous activity of motoneurones (Drake & Stavraky, 1948;Teasdall & Stavraky, 1953). Complete nervous isolation of a spinal cord segment in puppies, by intradural and bilateral section of lumbar and sacral dorsal roots plus cord transections above and below the de-afferented segment, also does not induce spontaneous activity of motoneurones in dogs surviving 2-6 months (Tower, 1937). This led Tower to conclude that 'autochthonous' activity is not a property of the mammalian spinal cord.…”