FIGURE 4.

Formaldehyde concentration dependence in vivo of multi‐unit activity in sural nerve filaments of anesthetized Sprague‐Dawley rats. (a) Formaldehyde 42–333 mM was injected into the lateral foot edge evoking prolonged biphasic mass activity in the sural nerve filaments which was dominated in phase 1 by tall spikes missing in phase 2; the second phase appeared only above 42 mM. Data are mean ± SEM (b) Concentration‐dependence of both phases. The lowest concentration with a significant difference to the saline control (NaCl) was formaldehyde 83 mM. In the box plots the median is indicated by thick lines, boxes indicate 25–75 percentiles and whiskers 10–90 percentiles