Cannabinoid receptors expression in the rat uterus during implantation.

SORDELLI MS, CERVINI M, FARINA M, BILLI S, FRANCHI AM, RIBEIRO ML.

Los Cocos, Córdoba, Argentina

Simposio; III Simposio Latinoamericano de Interacción Materno Fetal y Placenta: de la Investigación a la Clínica (III SLIMP).; 2007

Anandamide (AEA) is an endocannabinoid that exerts its action through cannabinoid receptors type 1 (CB1) and type 2 (CB2), besides vanilloid receptors. High concentrations of AEA are toxic both for implantation and embryo development, suggesting that AEA is an important modulator of the processes that occur during early pregnancy. Although it has been described that CB1 is expressed in mice uteri at early gestation, there are no reports about CB2. Thus, the aim of the present study was to characterize CB2 expression in the rat uterus during the peri-implantation period. Wistar rats were sacrificed on days 4, 5 and 6 of gestation. On day 6, implantation and inter-implantation sites were separated. To study if the blastocyst participates in the modulation of CB2 expression, we also analyzed its expression in the uterus from delayed implantation (rats on day 4 of pregnancy were ovariectomized and treated with vehicle, progesterone (P, 2 mg/kg) or 17b-estradiol (E, 0.1 mg/kg) and sacrificed on day 8 of gestation) and pseudopregnant rats (psp, prepuber rats were injected with 50 IU of equine chorionic gonadotropin and sacrificed on days 4 to 6 of psp). We observed that CB2 was expressed in the uterus from pregnant rats in all the days analyzed and that it was maximun on day 5 of gestation, the day in which implantation takes place. While CB2 expression remained unchanged in the uterus from psp rats (a model in which the blastocyst is absent), it was modulated in the delayed implantation rat uterus: the administration of E maintained CB2 expression high when compared with P treatment. Overall, these results suggest that CB2 expression might participate in AEA effects during implantation and that the blastocyst could be part of this regulation.