Extended Data Fig. 2: Effects of psilocybin on structural plasticity in frontal cortical PT and IT neurons.

a, b, Potential differential effect of psilocybin on dendritic spine head width in frontal cortical PT and IT neurons. Spine head width in the apical tuft of PT neurons (a) after psilocybin (yellow; 1 mg/kg, i.p.) or saline (grey) across days, expressed as fold-change from baseline in first imaging session (day -3). b, Similar to (a) for IT neurons after psilocybin (purple) or saline (light purple). There was cell-type difference in psilocybin’s effect on spine head width (interaction effect of treatment × time × cell type: P = 0.007, mixed effects model). These results show that PT neurons have a more pronounced increase in spine head width than IT neurons, indicative of a strengthening of excitatory connections in addition to gaining new inputs for PT neurons. This enlargement in spine head for PT neurons was less durable than the changes in spine density, returning to baseline after 35 days. We note the results should be interpreted with the consideration that the spine head width is near the spatial resolution limit for in vivo two-photon microscopy. c, Density of dendritic spines in the apical tuft of PT neurons after psilocybin (yellow; 1 mg/kg, i.p.) or saline (grey) across days. d-f, Similar to (c) for spine head width, formation rate, and elimination rate. g-j, Similar to (c-f) for IT neurons. These figure panels correspond to Fig. 1i–n and panel (a,b in this figure), except here across-dendrite values are shown, without taking advantage of the longitudinal data for within-dendrite baseline normalization. n = 8 mice (PT neurons, saline), n = 9 mice (PT neurons, psilocybin) in (a, c-f). n = 8 mice (IT neurons, saline), n = 8 mice (IT neurons, psilocybin) in (b, g-j). k-r, Psilocybin effects on structural plasticity in PT and IT neurons by sex of the animals. k, Density of dendritic spines in apical tuft of PT neurons in female (top row) and male mice (bottom row) after psilocybin (1 mg/kg, i.p.) or saline across days, expressed as fold-change from baseline in first imaging session (day -3). l, Similar to (k) for spine head width. m, Spine formation rate determined by number of new and existing spines in consecutive imaging sessions across two-day interval, expressed as difference from baseline in first interval (day -3 to day -1). n, Similar to (m) for elimination rate. n = 4 mice (PT neurons, saline, female), n = 4 (PT neurons, psilocybin, female), n = 4 (PT neurons, saline, male), n = 5 (PT neurons, psilocybin, male) in (k-n). o-r, Similar to (k-n) for IT neurons in female (top row) and male mice (bottom row). n = 5 mice (IT neurons, saline, female), n = 5 (IT neurons, psilocybin, female), n = 3 (IT neurons, saline, male), n = 3 (IT neurons, psilocybin, male). We did not detect effect of sex for any of the measures (interaction effect of treatment × sex × cell type, indicated in plots, mixed effects model). s-v, Psilocybin has no effect on spine protrusion length. s, Protrusion length of dendritic spines in apical tuft of PT neurons for all mice (left), or separately plotted for females (middle) and males (right), after psilocybin (1 mg/kg, i.p.) or saline across days, expressed as fold-change from baseline in first imaging session (day -3). t, Similar to (s) for IT neurons. Psilocybin had no detectable effect on spine protrusion length (main effect of treatment: P = 0.309, mixed effects model). u, Protrusion length of dendritic spines in apical tuft of PT neurons for all mice after psilocybin (1 mg/kg, i.p.) or saline across days, without taking advantage of the longitudinal data for within-dendrite baseline normalization. v, Similar to (u) for IT neurons. n = 8 mice (PT neurons, saline, 4 females, 4 males), n = 9 (PT neurons, psilocybin, 4 females, 5 males) in (s, u). n = 8 (IT neurons, saline, 5 females, 3 males), n = 8 (IT neurons, psilocybin, 5 females, 3 males) in (t, v). Data are mean and s.e.m. across dendrites. *, p < 0.05. ***, p < 0.001, post hoc with Bonferroni correction for multiple comparisons. Detailed sample size n values are provided in Methods. Statistical analyses are provided in Supplementary Table 1.

Source Data