Drug-Induced Hyperglycemia as a Potential Contributor to Translational Failure of Uncompetitive NMDA Receptor Antagonists

Hyperglycemia rather than the circadian phase during which stroke occurs determines the ischemic infarction volume. A, Blood was collected to measure blood glucose concentrations from mice in the daytime group (ZT3–ZT9; sleep cycle for mice) or the nighttime group (ZT15–ZT21; awake cycle for mice), the latter group received either a saline or glucose injection (2.2 g/kg, i.p.) 20 min before blood collection; n = 11–13 per group. B, Blood was also collected 60 min postischemia in a subset of mice in A; n = 6 per group. In A, B, ***p < 0.001, one-way ANOVA followed by Tukey’s multiple comparisons test; n.s. indicates no significant difference. C, D, The mice from A underwent cerebral ischemia induction by dMCAO immediately following blood collection, and the ischemic infarction volume was assessed 24 h postischemia. Data were analyzed by linear regression (C) or one-way ANOVA followed by Tukey’s multiple comparisons test (D). E, Same as D, except infarct was normalized to account for potential brain edema. In D, E, n = 10–11 per group; *p < 0.05, **p < 0.01, one-way ANOVA followed by Tukey’s multiple comparisons test; n.s. indicates no significant difference. F, Representative images of coronal brain sections of mice from C, D. Functional brain tissue was stained red by TTC, and the infarct area remained pale white and unstained.

MK801 increases blood glucose and the ischemic infarction volume in hyperglycemic mice in which stroke was induced. A, Blood was collected to measure the blood glucose concentrations of hyperglycemic mice pretreated with either saline or MK801 (4 mg/kg, i.p.) in the daytime group (ZT3–ZT9; sleep cycle for mice). Saline or MK801 was administered 60 min before blood collection, and mice were rendered hyperglycemic by a glucose injection (2.2 g/kg, i.p.) 20 min before blood collection; n = 12 per group. B, The mice from A underwent cerebral ischemia induction by dMCAO immediately following blood collection, and the ischemic infarction volume was assessed 24 h postischemia; n = 11 per group. C, Same as B, except infarct was normalized to account for potential brain edema; n = 11 per group. In A–C, *p < 0.05, **p < 0.01, Student’s t test. D, XY plot of data from A, B. E, Representative images of coronal brain sections of mice from B. Functional brain tissue was stained red by TTC, and the infarct area remained pale white and unstained.

Uncompetitive but not competitive antagonists of the NMDAR increase blood glucose in normoglycemic and hyperglycemic mice. A, Experimental timeline. Blood was collected before any treatments (baseline) and 40 min after injection of NMDAR antagonists: AP5 (10 mg/kg, i.p.), MK801 (4 mg/kg, i.p.), or CPP (10 mg/kg, i.p.); thereafter, the mice received a glucose injection (2.2 g/kg, i.p.) to induce hyperglycemia, and blood was once again collected 20 min after glucose injection. B, Glucose concentrations of blood collected as described in A; n = 6–7 per group; *p < 0.05, ***p < 0.001, one-way repeated-measures ANOVA, matching blood collected from the same mouse, followed by Tukey’s multiple comparisons test.

Ketamine increases blood glucose and the ischemic infarction volume in hyperglycemic mice subjected to stroke. A, Blood was collected to measure the blood glucose concentrations of hyperglycemic mice pretreated with either saline or ketamine (10 mg/kg, i.p.) in the daytime group (ZT3–ZT9; sleep cycle for mice). Saline or ketamine was administered 60 min before blood collection, and mice were rendered hyperglycemic by a glucose injection (2.2 g/kg, i.p.) 20 min before blood collection; n = 18–19 per group. B, The mice from A underwent cerebral ischemia induction by dMCAO immediately following blood collection, and the ischemic infarction volume was determined 24 h postischemia; n = 16 per group. C, Same as B, except infarct was normalized to account for potential brain edema; n = 16 per group. In A–C, *p < 0.05, ***p < 0.001, Student’s t test. D, XY plot of data from A, B. E, Representative images of coronal brain sections of mice from B. Functional brain tissue was stained red by TTC, and the infarct area remained pale white and unstained.