Fig. 6: Blockade of dendritic Ca²⁺ spikes reduces spine elimination.

a Schematic of local injection of MK801 into the layer 1 of the mouse cortex under a two-photon microscope. b, d Local and brief injection of MK801 at the beginning of each REM sleep episode, but not during NREM sleep, significantly reduced the number of dendritic Ca²⁺ spikes during REM sleep as compared to that in undisturbed REM sleep in both V1 b (n = 4 mice, P < 0.0001 and = 0.0362 for REM + MK801 vs. undisturbed REM sleep and REM after NREM + MK801, respectively) and FrA (d) (n = 4 mice, P = 0.0017 and = 0.00097 for REM + MK801 vs. undisturbed REM sleep and REM after NREM + MK801, respectively) (paired t test, two-sided). c, e MK801 injection at the beginning of a REM sleep episode, but not during NREM sleep, significantly blocked the integrated activity of dendritic Ca²⁺ spikes during REM sleep as compared to that in undisturbed REM sleep in both V1 (c) (P = 0.0001 and = 0.0199 for REM + MK801 vs. undisturbed REM sleep and REM after NREM + MK801, respectively) and FrA (e) (P = 0.0003 and < 0.0001 for REM + MK801 vs. undisturbed REM sleep and REM after NREM + MK801, respectively) (Wilcoxon–Mann–Whitney test, two-sided). f Schematic of experimental design to examine the effect of blocking dendritic Ca²⁺ spikes on spine elimination induced by MD in V1. g MD-induced dendritic spine elimination was significantly reduced after brief MK801 injection in REM sleep over a 4-h period as compared to that in NREM-d mice (n = 4 mice for REM + MK801; n = 5 mice for NREM + MK801, P = 0.0159, Wilcoxon–Mann–Whitney test, two-sided). h Schematic of experimental design to examine the effect of blocking dendritic Ca²⁺ spikes on spine elimination induced after FC in FrA. i Brief injection of MK801 during REM sleep, but not during NREM sleep, reduced FC-induced dendritic spine elimination (n = 5 mice for REM + MK801; n = 7 mice for NREM + MK801, P = 0.0025, Wilcoxon–Mann–Whitney test, two-sided). *P < 0.05, **P < 0.01 ***P < 0.001. Data are presented as mean ± s.e.m. In (c) and (e), each circle represents one active dendrite, n = 29, 94, and 108 dendrites for REM + MK801, undisturbed REM sleep and REM after NREM + MK801, respectively in V1; n = 32, 158 and 144 dendrites for REM + MK801, undisturbed REM sleep and REM after NREM + MK801, respectively in FrA. Source data for (b–e), (g) and (i) are provided as a Source Data file.