Changes of plasma and gene expression levels of ghrelin and leptin in rats receiving kisspeptin and morphine

Kisspeptin is a hypothalamic peptide which stimulates hypothalamus- pituitary- gonadal (HPG) axis. Morphine is an alkaloid which suppresses reproduction. Ghrelin and leptin are metabolic peptides which play role in relaying information to the HPG axis. In the present study, the interaction effects of kisspeptin and morphine were investigated on plasma and gene expression levels of leptin and ghrelin. Twenty adult male Wistar rats in four groups received injection of saline, kisspeptin (1nmol), morphine (5mg kg-1) or kisspeptin+ morphine. Rats received kisspeptin and morphine via third cerebral ventricular and subcutaneous injection respectively. Ten male rats in two groups received intravenous injection of saline or kisspeptin (7/5nmol). Blood samples, hypothalamic and adipose tissue samples were collected. Plasma and gene expression levels of ghrelin and leptin were measured by using the methods of enzyme-linked immunosorbent assay and real time-PCR respectively. Morphine significantly increased plasma concentration and hypothalamic mRNA levels of ghrelin compared to saline while kisspeptin significantly decreased them compared to saline. Morphine significantly decreased plasma and mRNA levels of leptin in adipose tissue compared to saline but kisspeptin did not increase plasma and mRNA levels of leptin in adipose tissue compared to saline. Kisspeptin significantly decreased the effects of morphine on plasma concentration and hypothalamic gene expression levels of ghrelin compared to alone morphine but it did not affect morphine’s influence on plasma and leptin gene expression levels compared to alone morphine. Kisspeptin and morphine may be involved in the regulation of reproductive activity partly via regulation the metabolic hormones synthesis.