Unilateral brain damage after focal ischemia. Extent of the smallest (dark gray), average (medium gray), and largest (light gray) lesions in saline- (left) and inosine- (right) treated animals 4 weeks after induction of focal ischemia. M1, M2, Primary and secondary motor areas; S1, S2, primary and secondary somatosensory areas.

Inosine enhances functional recovery after stroke. Animals were trained to retrieve food pellets through a restricted opening with either paw before surgery and were then tested weekly beginning 1 week later by a blinded observer. Scores are reported as percentage of preoperative performance. a, Inosine improves functional recovery using the impaired paw. b, Animals show normal performance with the unimpaired paw after 2 weeks regardless of treatment. *, **, ***Differences significant at p < 0.05, p < 0.01, p < 0.001, respectively. Error bars represent SEM.

Inosine alters gene expression in corticospinal neurons contralateral to the stroke. a, Heat-map showing patterns of changes induced by stroke alone (stroke + saline) and by inosine treatment after stroke (stroke + inosine). Only genes with statistically significant (p < 0.01) changes ≥1.7× above or below baseline level of expression are shown. Inset shows color scheme for the magnitude of changes. b, Pie chart showing numbers of genes exhibiting different patterns of change after stroke. Most changes follow the trend of being upregulated or downregulated after stroke and attenuated (atten.) by inosine (ino). A smaller number of genes are not significantly changed by stroke but are either upregulated or downregulated by inosine, and an even smaller number are changed by stroke and changed further in the same direction by inosine. c, Scatter diagram showing effect of inosine in attenuating stroke-induced changes. Data include only those genes whose expression is significantly altered by stroke. Data are plotted as the log₂ change in expression after stroke in animals treated with inosine versus saline (y-axis) against the log₂ change in expression after stroke alone (and treatment with saline) versus normal controls. Trend line has a slope of −0.49 and correlation coefficient of 0.87, signifying that inosine attenuates most of the stroke-induced changes. d. Scatter diagram similar to that of c, but showing all data points. Points that fall significantly off the trend line (p < 0.01, red dots) correspond to genes that are affected by inosine over and above attenuating the stroke-induced changes.

Inosine enhances CST sprouting on the denervated side of the spinal cord. a, a′, Low-magnification camera lucida drawings of BDA-labeled CST fibers that originate in the uninjured hemisphere and project to the side of the spinal cord denervated by unilateral cortical injury. Rats were treated with either saline (a) or inosine (a′). b, b′, High-magnification photomicrographs of fibers in the gray matter of saline- (b) and inosine- (b′) treated rats. c, c′, Camera lucida tracings of the fibers in b and b′. d, d′ (insets), Higher magnification views of bouton-like structures. e, f, Quantitation of ipsilaterally projecting CST fibers ≥40 μm in length in the transverse plane in the denervated dorsal funiculus and gray matter, respectively. g, Quantitation of ipsilaterally projecting CST fibers ≥200 μm in length in the denervated gray matter. h, Quantitation of bouton-like swellings on fibers projecting to the ipsilateral spinal gray matter visualized under a 100× oil objective. Results in e–g are normalized by the intensity of staining in the intact CST and are reported as number of labeled axons per mm length of spinal cord. **Difference between groups significant at p < 0.01. Error bars represent SEM.

Functional improvements persist after the cessation of treatment. a, b, Animals were treated as in Figure 3 but were tested for an additional 4 weeks after treatments ended with either the paw contralateral to the stroke (a) or the unaffected paw (b). Performance with the affected paw failed to improve after 3–4 weeks in saline-treated animals, but remained high and even tended to improve after inosine treatment ended. b, Performance with the paw ipsilateral to the stroke is unaffected by treatment. *, **, ***Differences between groups significant at p < 0.05, p < 0.01, p < 0.001, respectively. Arrows indicate time of pump removal.

Inosine-induced changes in protein expression. Immunohistochemistry was used to investigate whether inosine-induced changes found at the mRNA level translate into changes at the protein level. Analyses were performed in layer 5 of the uninjured forelimb motor cortex 7 d after a stroke was induced in the corresponding region of the contralateral hemisphere. a–c, Inosine induced changes in levels of complement proteins C1q (a) and C3 (b) and metallothionine (c). Arrows in a and b point to outline of labeled cells; inset in c shows labeled cells at higher magnification.