Effects of temperature on conduction in single vagal and saphenous myelinated nerve fibres of the cat.

Abstract

There have been several studies on the effects of temperature on the responses in single myelinated nerve fibres, e.g. Bremer & Titeca (1934), Schoepfle & Erlanger (1941), Lorente de No (1947), Tasaki & Fujita (1948), Hodler, Stampfli & Tasaki (1951), Tasaki (1949, 1953), Tasaki & Frank (1955), and more recently Inman & Peruzzi (1961) and Ishiko & Loewenstein (1961). However, although a great deal of valuable information has arisen out of the above investigations, there are still certain gaps in our knowledge, notably on the comparative effects of temperature on fibres of different diameters. For example, it is known that the absolute refractory period ends at the end of the spike at all measured temperatures (Adrian 1921; Amberson, 1930; Tasaki, 1949), but practically nothing is known as to how it varies in fibres of different diameters at different temperatures. Nor is there any information about the relative rates of recovery of excitability or conduction velocity after an impulse in fibres of different diameters. Further, there is no information about the maximum frequency of discharge that fibres of different diameters can conduct through a region of cooled nerve at different temperatures. Such information would be valuable because cold block is used extensively to block certain reflex effects, and the interpretation of such experiments would be greatly aided by such knowledge. Some information concerning this and other aspects of conduction in nerve fibres has been obtained and is presented in this paper. In the previous paper (Paintal, 1965) it was shown that temperature has no differential blocking effects on fibres of different diameters. In this paper it will be shown that it does have a differential effect on certain other aspects of nerve conduction and recovery processes. In this paper the expression 'absolute refractory period' has been used in the sense given to it originally by Adrian, i.e. it is the least interval after