Fig. 1: AAV-Flex-DTA induced deletion of DR^Sert neurons.

The experimental strategy involved (a) injection of the viral vector that produced Cre-dependent expression of the diphtheria toxin A subunit (b) in the dorsal raphe of Sert-Cre-::L10 mice or wild-type littermates (WT). Injection of the vector deleted nearly all serotonergic neurons at the injection site in the Sert-Cre animals. This is seen in (c) the top row showing three levels from rostral-to caudal from an intact animal and the lower row from an animal that received an injection of the vector. Note that at low magnification (left) with brown immunostaining for serotonin, that the DR contains almost no surviving neurons, while the MR is largely intact. At higher magnification (right panels) fluorescence images show the location of the injection site (marked by red stained intact non-serotonergic neurons) and that there are no surviving serotonin neurons within the boundaries of the red injection site. The loss of DR^Sert and MR^Sert neurons after DR injections sites (d), n = 9; DR-DTA, neuronal counts from each mouse is represented in left panel of d, with average percentage of neuronal survival on the right), where DR-DTA group (n = 9); WT (n = 3); MR-DTA (n = 4) were significantly different (F_1,8 = 126.6; P < 0.001, One-way ANOVA with multiple comparisons). After MR injection sites (e), MR-DTA (n = 4) is compared with intact WT animals (n = 3) and DR-DTA (n = 9), and these groups showed significant difference (F_1,5 = 86.5; P < 0.001, one-way ANOVA with multiple comparison). The error bars in d and e represent the standard error of mean (SEM). ***represents P < 0.001, one-way ANOVA to compare the groups in d and e. Cerebral aqueduct, aq; dorsal raphe, DR; median raphe, MR. Fig. 1a shows a drawing of the mouse brain at the level of the mid-DR (equivalent to plane −4.6 mm from bregma, of the mouse brain atlas)⁵³.