The relationship between ischaemic conduction failure and conduction velocity in cat myelinated axons

Abstract

SUMMARYUnitary action potentials have been recorded from cat spinal root filaments following electrical stimulation of hindlimb peripheral nerves. Potentials were monitored both before and during the ischaemia which follows the onset of cardiac arrest. The relationship between time to conduction failure (survival time) and initial conduction velocity was detennined for 164 nerve fibres. This revealed that during ischaemia, slow myelinated axons tend to fail before fast myelinated axons. The average survival time was 24 6 min (range 11-39 min). The results are discussed in terms of (i) the possible mechanisms underlying ischaemic conduction block,(ii) their clinical implications for the role of ischaemia in peripheral neuropathies, and (iii) using ischaemia as an experimental technique to produce a differential nerve block.

The contribution of ischaemia and deformation to the conduction block generated by compression of the cat sciatic nerve

“…Dissection, stimulation and recording techniques were all very similar to those experimnents described in the companion paper (Fern & Harrison, 1994) (Fern & Harrison, 1994 A separate series of cxperilmlelnts xALs perfor-imed to examiiine the effects of a imiore severe degree of compression. Figure 3B is a plot of surxival tlime folloxing infl.ation of the b.alloon to 250 nimlmlg of pressure (the higher degree of comilpr-ession) against coniductioni xelocity for 226 actionl potentiLals i-eco-rded fr-omil four cats.…”

“…Previous reports have suggested that nerve deformation and nerve ischaemia are two important factors during nerve compression. The pattern of effect of pure nerve deformation in frog nerve (Fern & Harrison, 1990) and pure ischaemia of cat nerve (Fern & Harrison, 1994) is compared with that of low and high degrees of compression of cat nerve in Fig. 5.…”

“…(Fern & Harrison, 1991, 1994. A preliminary report of some of the findings has been presented (Fern & Harrison, 1990).…”

“…In addition to deformation, the compressed nerve also becomes ischaemic as blood flow through nutritive vessels is occluded (Gelberman et al 1981(Gelberman et al , 1983Rydevik, Lundborg & Bagge, 1981;Lundborg, Gelberman, Minteer-Convery, Lee & Hargens, 1982;Matsumoto, 1983;Ogata & Naito, 1986). Indeed, ischaemia might be the essential factor in some forms of nerve compression disorders (Sunderland, 1976;Hargens, Romine, Sipe, Evans, Mubarak & Akeson, 1979;Lundborg et al 1982;Powell & Myers, 1986;Kalichman & Myers, 1991 Thus, nerve deformation, provided it is not extreme, has a differential action upon fast myelinated axons, while these large fibres are particular-ly resistant to the effects of ischaemia (Fern & Harrison, 1991, 1994). …”

Changes of wide dynamic range neuronal responses to mechanical cutaneous stimuli following acute compression of the rat sciatic nerve

“…A tungsten electrode (2)(3)(4)(5)(6)(7)(8) was positioned on the surface of the lumbar spinal enlargement at segments L4-6, and was advanced to a depth of 500-1000 µm to search for dorsal horn neurons. The activities of neurons were evoked by tapping and stroking the hindpaw as the electrode was lowered.…”