Hypothalamic arginine vasotocin and isotocin are involved in stress response in fish

Resumen de la presentación de un póster en: 26th Congress of the new European Society of Comparative Biochemistry and Physiology (2009, 6-9 september, Innsbruck, Austria). Session 5: The role of stress in organism performance, development and evolution.

Arginine vasotocin (AVT) and isotocin (IT) are fish nonapeptides synthesized in hypothalamic neurones, from where they are transported to neurohypophysis for storage and release to circulation. Vasotocinergic and isotocinergic fibers, abundant in different extrahypothalamic areas of the brain, suggest peptides' action as neurotransmitters and/or neuromodulators. Changes in hypothalamic, pituitary and plasma AVT and IT concentrations were found in fish subjected to different type of stress, i.e. confinement, disturbance, high density (HD) or food deprivation (FD). An effect of stress on nonapeptides' synthesis and release depends on the type of stress stimuli. In sea bream, HD has been shown to be a strong stimulus for release of AVT and IT from pituitary to circulation; FD affects hypothalamic synthesis of both nonapeptides. These results show a parallel response of AVT and IT to HD and FD, and point to a joint mechanism of regulation. On the other hand, in three-spined stickleback kept at high density, higher concentrations of AVT in males' brain and higher concentrations of IT in females' brain have been found. It points to separate mechanisms of nonapeptides' regulation. The distinct control mechanisms of AVT and IT have also been shown in rainbow trout exposed to disturbance stress. Nonapeptides' functions linked to stress response require activation of central and peripheral mechanisms. Adrenocorticotropic action of AVT has been demonstrated in fish. Thus nonapeptides probably affect the hypothalamic–pituitary–interrenal stress axis. The model of AVT and IT action in fish response to stress has been proposed.

Peer reviewed