Fig. 1.

A: Research design. At least 20 days after implantation surgery, rats were exposed to the control mode for 20 days and then to the H-reflex down-conditioning mode for 50 days. The inferior olive (IO) was then ablated. After the ablation, exposure to the down-conditioning mode continued for 56–102 more days. The last 10 control-mode days, the 10 down-conditioning days just before IO ablation (i.e., days 41–50 of conditioning), and the last 10 days of continued down-conditioning after IO ablation (heavy horizontal lines) provided the data used to assess the effect of down-conditioning on the soleus H-reflex and the final impact of IO ablation on the maintenance of soleus H-reflex down-conditioning. B: IO ablation. Cresyl-violet stained photomicrographs showing the IO nucleus complex and IO neurons in a naive control (NC) rat (B1 and B3) and in an IO-ablated rat (IO rat; B2 and B4). (B3 and B4 show the areas outlined in B1 and B2, respectively.) DAO, dorsal accessory olive; DM, dorsomedial group; MAO, medial accessory olive; PO, principal olive. Scale bars: 400 μm in B1 and B2, 40 μm in B3 and B4. The loss of most IO neurons in the IO-ablated rat is evident. C: VGLUT2 immunoreactivity (VGLUT2-IR) in cerebellar cortex. C1 and C2: photomicrographs of VGLUT2-IR-labeled cerebellar sections showing VGLUT2-IR labeling in cerebellar cortex from a NC rat (C1) and an IO rat (C2). The molecular (M), Purkinje (P), and granular (G) layers are indicated. VGLUT2-IR in the molecular layer is much weaker in the IO rat (C2). Scale bar: 100 μm. C3: correlation in IO rats between cerebellar VGLUT2-IR intensity in the molecular layer and remaining IO neurons (in % of NC neuron number). The strong correlation (r = 0.80, P < 0.01) is consistent with the fact that VGLUT2-IR labeling in the molecular layer is selective for excitatory olivocerebellar climbing fiber terminals on Purkinje cell dendrites (Fremeau et al. 2001; Kaneko et al. 2002).