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Reproductive processes in fishes are regulated by the hypothalamic-pituitary-gonadal (HPG) axis, much like in tetrapods. Within this system, Gonadotropin-Releasing Hormone (GnRH) is released by the hypothalamus, binding to GnRH receptors in the pituitary gland and stimulating the secretion of gonadotropin hormones. The current study aimed to analyze the GnRH receptor in Oncorhynchus mykiss (rainbow trout) using a computational and structural biology approach. The GnRH receptor gene of O. mykiss comprises a nucleotide sequence of 1707 base pairs with an open reading frame of 1251 base pairs, which is responsible for encoding 416 amino acids. It was found that the GnRH receptor contains leucine (L) as the most abundant amino acid. The secondary structure revealed that alpha helices constitute the largest percentage (36 %) with 153 residues, followed by extended strands with 77 residues (17.51 %). The GnRH receptor contains 26 negatively charged and 37 positively charged amino acid residues. The highest hydrophilicity was observed for lysine (K) at position 310, with a value of −3.900, while the highest hydrophobicity was found for leucine (L) at position 290, with a value of 3.80. Molecular docking analysis showed that the most favorable binding energy was observed for Gestrinone (−7.8 kcal/mol). Gestrinone was found to form hydrogen bonds with MET160, LUE245, LUE62, TYR216, and GLN209 residues of GnRH. Moreover, molecular dynamics revealed that the complexes form robust and enduring connections, indicating their structural integrity throughout the simulation. The results of this study provide insights into the protein modeling, molecular docking, and virtual screening of antagonist ligands against the GnRH receptor. Additionally, they may significantly aid in the advancement and improvement of therapeutic strategies targeted at treating various fish reproductive dysfunctions.

The present study is aimed at designing bilayer-floating tablets to improve the drug concentration in the stomach for enhanced therapeutic efficacy. The tablets are comprised of an upper layer of levofloxacin (466.5 mg) and a lower layer of famotidine (133.5 mg). Five formulations (F1-F5) were developed by using hydroxypropyl methylcellulose grades (K4M, K15M, and K100M) along with Carbopol 934. In the case of the effervescent system (F1-F3), sodium bicarbonate was added to impart buoyancy to the tablets; while in the case of noneffervescent formulations (F4 & F5), guar gum and xanthan gum were incorporated to induce flotation and swelling and retard the release of a drug. The precompression characteristics of tablets depict the suitability of all formulation powder for direct compression. The ATR-FTIR analyses have shown that the components of both effervescent and noneffervescent tablets are compatible with each other. The total weight of each tablet was 600 mg, with a weight variation of about ≤10 mg. Both the layers were smooth and flat with a thickness ranging from 3.16±0.04 to 3.54±0.01 mm. The diameters of prepared floating tablets were about 15 mm, optimum for oral administration. After adjusting the tablet’s hardness to 6-7 kg/cm2, its friability was found to be