Variation in Brain Arginine Vasotocin (AVT) and Isotocin (IT) Levels with Reproductive Stage and Social Status in Males of Three-spined Stickleback (Gasterosteus Aculeatus)

Arginine vasotocin (AVT) and isotocin (IT) are fish nonapeptides synthesized in separate hypothalamic neurons from where they are transported to the neurohypophysis for storage and release into circulation. AVT is known to modulate aggression, courtship and parental care or social communication in many species, including fish, amphibians and birds. In this paper we examined a link between the level of AVT and IT in the brain and particular reproductive behavior in males of three-spined stickleback (Gasterosteus aculeatus). AVT and IT levels in whole brain of males of three-spined stickleback vary depending on specific breeding behavior of the individuals and their social status. These studies have shown the highest AVT levels in aggressive males that took care of the eggs. Brain AVT concentrations are also increased in nuptial colored subordinate males that fight to change their social status. On the other hand, IT is significantly higher in aggressive dominant males that defend their territory. IT may be also involved in courtship in three-spined stickleback. These findings highlight the importance of determination of "free", bioavailable neuropeptides' level in behavioral studies.