The effect of stimulation and blockade of muscarinic receptors on the expression of GnRH and neuronal factors in GT1-7 cell line

Gonadotropin-releasing hormone (GnRH) is a tropic peptide synthesized and released from GnRH neurons in the hypothalamus and is responsible for the release of follicle-stimulating hormone and luteinizing hormone from the anterior pituitary. Very few studies show that cells responsible for GnRH release express cholinergic receptors. Studies on the levels of mRNA expression of neuronal factors and how GnRH release is affected by stimulation or blocking receptors are insufficient. In addition, there is no study on the effects of acetylcholine (ACh) and atropine (ATR) on these cells. Therefore, our study aimed to analyze the effects of stimulation and blockade of cholinergic receptors on neuronal factors and GnRH expression in GT1-7 cells. In our study, the effects of ACh and ATR at increasing concentrations were analyzed with the MTT test. The cells were exposed to 1-10-100 µM concentrations of ACh and ATR to determine the effects on neuronal factors and GnRH expressions. The changes in NGF, Nestin, β-tubulin III, and GDNF mRNA expressions in these cells were determined by RT-qPCR using RNA samples obtained from these cells. GT1-7 cells continued their proliferation at high concentrations of ACh, such as 10-1 M. In ATR exposure, the proliferation of cells decreased after a concentration of 10-3 M. In general, increasing concentrations of ACh resulted in increased expression of neuronal factors and accompanying GnRH mRNA. ATR, on the other hand, showed no significant effects on neither neuronal factors nor GnRH mRNA expressions. The increase with ACh indicates the activity of the cholinergic system in the GnRH release, but the mechanism of the increase in neuronal factors seems more complex. It seems likely that neuronal factors indirectly increase GnRH expression by receptor stimulation.