Expression of the cannabinoid receptor type 1 in the pituitary of rabbits and its role in the control of LH secretion C. Dall’Aglio a , P. Millán b , M. Maranesi c , P.G. Rebollar d , G. Brecchia c , M. Zerani e, * , A. Gobbetti f , G. Gonzalez-Mariscal g , C. Boiti c, d a Sezione di Anatomia, Dipartimento di Scienze biopatologiche veterinarie, Università di Perugia, Via S. Costanzo 4, 06126 Perugia, Italy b Departamento Fisiología Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Ciudad Universitaria, s/n, 28040 Madrid, Spain c Laboratorio di biotecnologie fisiologiche, Sezione di Fisiologia Veterinaria, Dipartimento di Scienze biopatologiche veterinarie, Università di Perugia, Via S. Costanzo 4, 06126 Perugia, Italy d Departamento Producción Animal, ETSI Agrónomos, Universidad Politécnica de Madrid, Ciudad Universitaria, s/n, 28040 Madrid, Spain e Scuola di Scienze mediche veterinarie, Università di Camerino, Via Circonvallazione 93, 62024 Matelica, Italy f Scuola di Bioscienze e biotecnologie, Università di Camerino, Via Gentile III da Varano, 62032 Camerino, Italy g Centro de Investigación en Reproducción Animal, CINVESTAV-Universidad Autónoma de Tlaxcala, Mexico article info Article history: Received 31 May 2013 Received in revised form 20 August 2013 Accepted 21 August 2013 Keywords: CB1 Endocannabinoids Rimonabant LH Rabbit abstract The aim of this study was to elucidate the possible direct regulatory role of the endo- cannabinoids in the modulation of LH secretion in rabbits, a reflex ovulator species. The cannabinoid receptor type 1 (CB1) was characterized by RT-PCR techniques in the anterior pituitary of intact and ovariectomized does treated with GnRH and primed with estrogen and CB1 antagonist, rimonabant. Cannabinoid receptor type 1 immune reaction was evi- denced by immunohistochemistry in the cytoplasm of approximately 10% of the pituitary cells with a density of 8.5  1.9 (per 0.01 mm 2 ), both periodic acid–Schiff positive (30%) and negative (70%). All CB1-immunoreactive cells were also immune reactive for estrogen receptor type 1. Ovariectomy, either alone or combined with estrogen priming, did not modify the relative abundances of pituitary CB1 mRNA, but decreased (P < 0.01) the expression of estrogen receptor type 1 mRNA. Treatment with CB1 antagonist (rimona- bant) inhibited (P < 0.01) LH secretory capacity by the pituitary after GnRH injection, and estrogen priming had no effect. The present findings indicate that the endocannabinoid system is a potential candidate for the regulation of the hypothalamic-pituitary-ovarian axis in reflex ovulatory species. Ó 2013 Elsevier Inc. All rights reserved. 1. Introduction The endocannabinoids, arachidonoyl ethanolamide (anandamide) and 2-arachidonoyl-glycerol, together with the 7 transmembrane G protein–coupled cannabinoid receptor subtypes 1 (CB1) and CB2, form an endogenous signaling system involved in a large array of physiological functions [1–4]. Besides controlling food intake and energy balance [5], the endocannabinoid system modulates several neuroendocrine functions, including the hypothalamic- pituitary gonadal and adrenal axes [6–9]. For instance, injections of delta-9-tetrahydrocannabinol (delta-9-THC) to rhesus monkeys [10] or rabbits [11], as well as administra- tion of delta-1-THC to proestrus rats [12], inhibit gonado- tropin release and ovulation, an effect that apparently occurs at the level of the hypothalamus. Moreover, anan- damide and 2-arachidonoyl-glycerol inhibit LH and prolactin secretion in vivo and in vitro, although with different efficacy [13,14]. Both endocannabinoids have been identified in the anterior pituitary and the hypothalamus of rats, suggesting that these endogenous compounds may be synthesized also locally [15,16]. However, CB1 is widely * Corresponding author. Tel.: þ39 737 403463; fax: þ39 737 403402. E-mail address: massimo.zerani@unicam.it (M. Zerani). Contents lists available at ScienceDirect Domestic Animal Endocrinology journal homepage: www.domesticanimalendo.com 0739-7240/$ – see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.domaniend.2013.08.004 Domestic Animal Endocrinology 45 (2013) 171–179