Dopamine decreases the stimulatory effects of kisspeptin on serum LH hormone concentrations in male rats

Dopamine inhibits hypothalamus-pituitary-gonadal (HPG) axis. Kisspeptin/ GPR54 signaling pathway increases GnRH/LH release and testosterone secretion. In the present study the effects of interaction between dopamine and kisspeptin on mean serum LH concentrations in rats were investigated.

Forty-five male Wistar rats weighing 230-250g in nine groups (n = 5 in each group) received saline, kisspeptin (0.1 or 1 nmol), P234 (1nmol), dopamine (2 or 5 µg/Kg), simultaneous injection of kisspeptin and P234, dopamine and kisspeptin, or dopamine and P234, via third cerebral ventricle. Blood samples were collected 1 hour after injections. Mean serum LH concentrations were determined by radio-immuno assay (RIA).

Kisspeptin significantly increased serum LH concentration while dopamine decreased LH concentration. Peptide 234 blocked the stimulatory effects of kisspeptin on LH concentration. Compared to kisspeptin, LH concentration significant decreased by kisspeptin and dopamine. However, kisspeptin and dopamine significantly increased LH concentration compared to dopamine alone. Simultaneous injections of dopamine and P234 significantly decreased LH concentration compared to kisspeptin or simultaneous injections of dopamine and kisspeptin.

Dopamine exerts inhibitory effects on kisspeptin signaling pathway at hypothalamic levels and thereby it decreases the stimulatory effects of kisspeptin on reproductive axis.