FIG. 1.

Location of recorded neurons and their intrinsic properties in SCI mice. (A) Schematic showing the location of recorded neurons on a horizontal slice. Light and dark gray shading represent gray and white matter, respectively, which are clearly visible under infrared differential interference contrast optics. Neurons from untrained (red circles) and trained (blue circles) mice were recorded one to two segments rostral and caudal to the hemisection (dashed rectangle: made between T10 and T11 spinal nerves). Recording location, relative to the lesion, was divided into five regions: ipsilateral-rostral (IR), ipsilateral-caudal (IC), contralateral-rostral (CR), contralateral-caudal (CC), and contralateral-epicenter (CE; inside dashed rectangle). A bipolar stimulating electrode was placed in the dorsal columns at the rostral end of the slice (left) for stimulation of descending inputs. (B) Representative action potential (AP) showing inflection point (arrow, where dV/dt is >15–20 mV/ms) from which various measurements were made (see text). (C) Group comparisons for AP properties in untrained (red) and trained (blue) mice. These properties were not different in untrained and trained mice. Error bars=SEM on all bar charts. (D) Typical AP discharge patterns observed in response to square step depolarizing current injection (800 ms duration). Discharge patterns fall into four categories: tonic firing (TF), single spiking (SS), initial bursting (IB), and delayed firing (DF). (E) The incidence of each firing pattern did not differ in untrained (red) and trained (blue) mice. Color image is available online at www.liebertpub.com/neu