Kisspeptins Kiss1 and Kiss2 in fish modulate corticoliberin and gonadoliberin gene expression in brain structures of <i>Danio rerio</i>

BACKGROUND: The kisspeptin system in the brain is crucial for regulating reproductive functions in humans and animals. In contrast to mammals, the brains of Danio rerio express two types of kisspeptins — Kiss1 and Kiss2. The role of these kisspeptins in hormonal regulation in fish remains an important area of investigation. AIM: To examine the effects of Kiss1 and Kiss2 on corticoliberin and gonadoliberin gene expression in the midbrain and diencephalon of Danio rerio. MATERIALS AND METHODS: Kisspeptins Kiss1 and Kiss2 are oligopeptides consisting of 13 and 9 amino acid residues, respectively. Danio rerio fish were administered intracerebroventricular injections of 1 ng and 4 ng of each peptide at 1 μL volumes. At 1 and 4 hours post-administration, the fish brains were extracted, and the midbrain and diencephalon were isolated as a single complex. Gene expression levels of corticoliberin and gonadoliberin were analyzed using real-time polymerase chain reaction (PCR). RESULTS: Intracerebroventricular administration of Kiss1 and Kiss2 significantly modulated corticoliberin and gonadoliberin gene expression in the midbrain and diencephalon of Danio rerio. In the group injected with 4 ng of Kiss1, corticoliberin gene expression increased 17- and 65-fold after 4 hours compared to the control groups. In the group administered 1 ng of Kiss2, corticoliberin gene expression increased by 23- and 92-fold compared to the control groups after 1 hour. In the group administered 4 ng of Kiss1, gonadoliberin gene expression decreased threefold compared to the control group euthanized at 1 hour. In the group administered 1 ng of Kiss2, gonadoliberin gene expression decreased fourfold compared to the control group after 1 hour. In the group administered 1 ng of Kiss2, gonadoliberin gene expression decreased threefold compared to the control group after 4 hours. CONCLUSION: The experimental results reveal that Kiss1 and Kiss2 kisspeptins in Danio rerio stimulate corticoliberin gene expression while suppressing gonadoliberin gene expression in the midbrain and diencephalon.