Immunoreactivity of Rat Primary Afferent Neurones with C- and A-Fibres

Abstract

Sensory neurones are commonly classified into conduction velocity (CV) groups, the C-, Aδ - and Aα / β - fibre groups. If the functional significance of these groups is to become clear, the borderlines between the groups need to be clearly defined. However, fibres are sometimes classified as C on the basis of their CV in the periphery, although, as we show below, some of these may conduct in the Aδ range nearer the ganglion. Furthermore, an assumption is sometimes made that small dorsal root ganglion (DRG) neurones have C-fibres and thus that some peptides found predominantly in small neurones are only in C-fibre cells. However it has been shown in the rat that, although C-fibres arise from small neurones, A-fibres can arise from all sizes of neurones including the very small ones (Harper and Lawson 1985). Therefore, we have correlated the fibre CV of neurones directly with their immunoreactivity. The antibodies we have used are anti-substance P, anti-calcitonin gene related peptide, 2C5 and RT97.