Effects of central administration of arginine vasotocin on monoaminergic neurotransmitters and energy metabolism of rainbow trout brain

In a first set of experiments, intracerebroventricular (ICV) treatment of 1 mul 100g(-1) body mass of Cortland saline containing different doses (1-20 nmol mul(-1)) of arginine vasotocin (AVT) produced after 180 min dose-dependent changes in levels of brain neurotransmitters in several brain regions and pituitary of rainbow trout Oncorhynchus mykiss. Thus, an enhancement of serotonergic and dopaminergic activity, together with a decreased noradrenergic activity, were observed both in the hypothalamus and pituitary of AVT-treated fish. In the other brain regions assessed, only increased serotonergic activity in the optic lobes, and decreased dopaminergic activity in the telencephalon of AVT-treated fish were noticed. Changes observed in monoamine levels resemble those observed during osmotic adaptation of euryhaline fishes. In a second set of experiments, fish were ICV injected with AVT as described above to assess changes in several variables of brain energy metabolism. The results obtained show a dose-dependent enhancement of brain glycogenolytic potential in the brain of AVT-treated fish, that again resemble the changes observed in euryhaline fishes during osmotic acclimation. (C) 2004 The Fisheries Society of the British Isles.