Article Figures & Data
Figures
- Figure 1.
Spontaneous network activity of cortical neurons in culture. A, Distribution of basal burst rates (n = 65). Bars represent the number of recordings within individual 0.05 Hz bins. The distribution was well fitted by a single Gaussian function (black line; R2 = 0.77). B, Sample traces illustrating synchronous spontaneous bursting (upper panel). Application of NBQX and AP5 abolished network bursting (lower panel). C, Higher-resolution traces illustrating the network burst framed in B. D, Summary graph of the effect of NBQX + AP5 (n = 4) and of TTX (n = 4) on spontaneous network bursting.
- Figure 2.
Activation of CB1R on glutamatergic neurons inhibits network bursting. A, Histogram of normalized spontaneous burst rates in different experimental conditions. Connected circles represent individual experiments. WIN had no effect on average in naive conditions (n = 11) but significantly decreased bursting in disinhibited cultures (in Ptx + CGP; n = 8). This effect was prevented by AM251 (n = 4). B, Sample traces illustrating the inhibitory effect of WIN in the presence of Ptx and CGP. C, Summary histogram of the average effect of WIN in different experimental conditions in cultures from rat cortices (left) and in cultures from cortices of GABA-CB1R KO, Glu-CB1R KO, and their respective wild-type (wt) littermates (right).
- Figure 3.
Endogenous modulation of network activity by CB1Rs. Aa, Sample traces illustrating the excitatory effect of AM251. Ab, Sample traces from a different culture where AM251 caused a decrease in burst rates. B, Summary graph of 13 different experiments (left; connected symbols represent individual recordings). The bar on the right illustrates the average effect of AM251 on burst rates. C, Effect of AM251 expressed as a function of basal burst rate. AM251 increased bursting in cultures with lower basal burst rates (<0.35 Hz; n = 8; white circles), whereas it was inhibitory in cultures with higher basal burst rates (>0.35 Hz; n = 5; white squares). Bold symbols with error bars illustrate the averages for the two groups. Solid and dashed lines represent the linear regression and 95% confidence interval, respectively.
- Figure 4.
Basal level of network activity dictates direction of AM251 effect. A–C, Histograms of the effect of muscimol (A, n = 8), CTZ (B, n = 5), and 4-AP (C, n = 5) on spontaneous burst rates and of the effect of a subsequent application of AM251 (connected circles represent individual experiments). AM251 excited cultures with low basal burst rates (in muscimol), whereas it inhibited those with high basal burst rates (in CTZ and in 4-AP). D, Net effect of AM251 expressed as a function of basal burst rate. A significant inverse correlation was found when the data of all the AM251 experiments were pooled (n = 31). E, Histogram summarizing the effect of AM251 when inhibitory synaptic transmission was blocked. AM251 significantly increased bursting in Ptx (n = 6), had no effect in Ptx + CGP (n = 6), and significantly decreased bursting in Ptx + CGP + CTZ (n = 4). F, Net effect of AM251 expressed as a function of basal burst rate in disinhibited cultures. A significant inverse correlation was found when the data of all the AM251 experiments in disinhibited cultures were pooled (n = 16). Bold symbols with error bars represent the averages for their respective experimental conditions. Solid and dashed lines represent the linear regression and 95% confidence interval, respectively.
