The endogenous cannabinoid, anandamide regulates anterior pituitary secretion in vitro

The present study was aimed to test whether the endogenous ligand for the cannabinoid receptor, anandamide (ANA) could produce direct effects on anterior pituitary (AP) hormone secretion in vitro. AP cells, dispersed in Krebs-Ringer, were treated with either (1) different concentrations of ANA, (2) with ANA after pre-treatment with the selective central cannabinoid receptor (CB1) antagonist, SR 141716 (SR) or (3) with SR alone. After 30 min of incubation the luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL), adrenocorticotroph hormone (ACTH) as well as growth hormone (GN), were measured in the culture media. All these hormone levels were affected with the exception of FSH, which did not change after the treatment. LH and PRL levels were decreased while ACTH and GH increased. The LH and PRL decrease were prevented by SR. SR did not antagonize the stimulatory effect exerted by ANA on ACTH and GH release from AP cells. We postulate that ANA inhibits or activates the release and/or synthesis of AP hormones. This activation may occur via CBI receptor in the case of LH and PRL; the other effects of the endogenous cannabinoids are probably mediated via another postulated (CBx) receptor for which SR is not an effective antagonist. The results indicate that ANA may influence AP hormone secretion, acting directly on the gland.