Effect of chronic undernourishment on the cord dorsum potentials and the primary afferent depolarization evoked by cutaneous nerves in the rat spinal cord

The effect of chronic undernourishment on the cord dorsum potentials (CDPs) and the dorsal root potential (DRP), closely related to primary afferent depolarization (PAD) and presynaptic inhibition in the spinal cord of the rat, was analyzed in this study. Single electrical pulses applied to the sural nerve (SU) of control (n=14) and chronically undernourished (n=16) Wistar rats produced CDPs, which are composed of four components: afferent volley (AV), two negative components (N(1) and N(2)), and one positive component (P wave) and negative DRPs recorded in a small rootlet of the L6 segment of the rat. The CDPs of the control and undernourished rats with AV components of comparable amplitude (U(AV)/C(AV)=0.96), showed N(1) components of similar amplitude (U(N1)/C(N1)=0.94), but smaller P wave (U(PW)/C(PW)=0.23). A comparable reduction in the amplitude of the DRPs was obtained in the undernourished rats (U(DRP)/C(DRP)=0.36). When normalized as a function of the body mass of the animals, the CDPs and DRPs produced in undernourished rats were of significantly smaller normalized amplitude than those evoked in the control. According to these results, it is suggested that chronic undernourishment induce a depressive effect on the mechanisms generating the P wave component in the CDP and the DRPs either by decreasing the sensory input and/or the excitability of the dorsal horn neurones involved in the generation of PAD and presynaptic inhibition in the spinal cord of the rat.