CB1 mRNA localization detected by Whole-mount in situ hybridization in whole zebrafish ovary. (A) Whole ovary transmitted light image; (A′) whole ovary green fluorescence image showing the localization of CB1 antisense mRNA probe; (A″) overlap of both previous images: stages III and IV showed the most abundant concentration of CB1 mRNA. The circle indicates the mature eggs with no fluorescence signal. (B) Negative control was performed with antisense probe pre-adsorbed with the sense probe in excess.

CB1 receptor synthesis during zebrafish oocyte maturation and in the brain used as positive control. Western blot analysis shows a signal corresponding to CB1 at 63 kDa, in brain and in class III oocytes. Light signal is visible in class IV, no signal in class V. β-tubulin was used as control protein.

CB1 ontogeny during zebrafish development. CB1 receptor mRNA starts to be expressed at 3 somites stage (B) while its relative protein starts to be synthesized at hatching time. β-tubulin was used as control protein (A). Different letters indicate significant differences (p < 0.05).

Morphological aspect of zebrafish embryos and larvae at 12, 24, 72 and 96 hpf. The developmental stages showed in the pictures were the same in the control group and in the two groups exposed to AM251 (10 and 20 nM) in all the stages analyzed. Scale bars: 500 mm.