Influence of Prolactin Secretion Changes on Sperm Head Size and Freezability in Ibex and Mouflon.

This work examined the influence of induced changes in prolactin (PRL) secretion on sperm cryoresistance of ibex and the mouflon. PRL secretion was modified in a first experiment by the use of bromocriptine (BCR, dopamine agonist) during the non-breeding season, and in a second experiment by the use of sulpiride (SLP, dopamine D-receptor antagonist) during the rutting season. Slow and ultra-rapid freezing protocols were used to cryopreserve sperm samples. BCR decreased blood plasma PRL concentrations, whereas SLP increased them. Cryoresistance ratios (CRs) for curvilinear velocity (VCL), straight-line velocity (VSL), and average path velocity (VAP) in BCR-treated mouflons were lower than in controls using slow-freezing ( < 0.05), while CRs of motility and morphologically normal sperm of BCR-treated mouflons were greater than controls with ultra-rapid freezing ( < 0.05). BCR increased the head sperm dimensions in ibexes ( < 0.001); conversely, BCR decreased the head dimensions in mouflons ( < 0.001). CR-motility, CR-amplitude of lateral head displacement (ALH), CR-viability, and CR-acrosome integrity in SLP-treated mouflons were lower than in controls with slow-freezing ( < 0.01); CR-viability and CR-acrosome were lower than controls with ultra-rapid freezing ( < 0.05). In ibexes, CR-ALH was lower for SLP-treated ( < 0.05). SLP treatment increased head dimensions in ibexes ( < 0.001) but did not affect the sperm head of mouflons. Our findings show that high levels of blood plasma PRL negatively affect the cryoresistance of ibex and mouflon sperm.