Dipartimento di Medicina Sperimentale sez F. Bottazzi, Seconda Università di Napoli, via Costantinopoli 16, 80138 Naples, Italy.
Am J Physiol Endocrinol Metab. 2012 Aug 15;303(4):E475-87. doi: 10.1152/ajpendo.00086.2012. Epub 2012 Jun 5.
Gonadotropin-releasing hormone (either GnRH1 or GnRH2) exerts a local activity in vertebrate testis, including human testis. Relationships between endocannabinoid (eCB) and GnRH systems in gonads have never been elucidated in any species so far. To reveal a cross-talk between eCBs and GnRH at testicular level, we characterized the expression of GnRH (GnRH1 and GnRH2) as well as GnRH receptor (GnRH-R1, -R2, and -R3) mRNA in the testis of the anuran amphibian Rana esculenta during the annual sexual cycle; furthermore, the corresponding transcripts were localized inside the testis by in situ hybridization. The possible endogenous production of the eCB, anandamide (AEA), was investigated in testis by analyzing the expression of its biosynthetic enzyme, Nape-pld. Incubations of testis pieces with AEA were carried out in the postreproductive period (June) and in February, when a new spermatogenetic wave takes place. In June, AEA treatment significantly decreased GnRH1 and GnRH-R2 mRNA, stimulated the transcription of GnRH2 and GnRH-R1, and did not affect GnRH-R3 expression. In February, AEA treatment upregulated GnRH2 and GnRH-R3 mRNA, downregulated GnRH-R2, and did not affect GnRH1 and GnRH-R1 expression. These effects were mediated by type 1 cannabinoid receptor (CB1) since they were fully counteracted by SR141716A (Rimonabant), a selective CB1 antagonist. In conclusion, eCB system modulates GnRH activity in frog testis during the annual sexual cycle in a stage-dependent fashion.
促性腺激素释放激素（无论是 GnRH1 还是 GnRH2）在脊椎动物睾丸中发挥局部作用，包括人类睾丸。迄今为止，在内分泌大麻素（eCB）和 GnRH 系统在性腺中的关系在任何物种中都没有得到阐明。为了揭示 eCB 和 GnRH 在睾丸水平上的相互作用，我们描述了在年度性周期中，蛙类两栖动物 Rana esculenta 睾丸中 GnRH（GnRH1 和 GnRH2）以及 GnRH 受体（GnRH-R1、-R2 和 -R3）mRNA 的表达；此外，通过原位杂交技术将相应的转录本定位在睾丸内。通过分析其生物合成酶 Nape-pld 的表达，研究了睾丸中内源性大麻素，即花生四烯酸乙醇胺（AEA）的可能产生。在繁殖后期（6 月）和发生新的精子发生波的 2 月，对睾丸进行 AEA 孵育。在 6 月，AEA 处理显著降低了 GnRH1 和 GnRH-R2 mRNA 的表达，刺激了 GnRH2 和 GnRH-R1 的转录，而不影响 GnRH-R3 的表达。在 2 月，AEA 处理上调了 GnRH2 和 GnRH-R3 mRNA 的表达，下调了 GnRH-R2 的表达，而不影响 GnRH1 和 GnRH-R1 的表达。这些作用是通过 1 型大麻素受体（CB1）介导的，因为它们被选择性 CB1 拮抗剂 SR141716A（利莫那班）完全逆转。总之，eCB 系统在年度性周期中以阶段依赖的方式调节青蛙睾丸中的 GnRH 活性。
