Brain serotonergic activation in growth-stunted farmed salmon: adaption versus pathology.
Signalling systems activated under stress are highly conserved, suggesting adaptive effects of their function. Pathologies arising from continued activation of such systems may represent a mismatch between evolutionary programming and current environments. Here, we use Atlantic salmon (Salmo salar) in aquaculture as a model to explore this stance of evolutionary-based medicine, for which empirical evidence has been lacking. Growth-stunted (GS) farmed fish were characterized by elevated brain serotonergic activation, increased cortisol production and behavioural inhibition. We make the novel observation that the serotonergic system in GS fish is unresponsive to additional stressors, yet a cortisol response is maintained. The inability of the serotonergic system to respond to additional stress, while a cortisol response is present, probably leads to both imbalance in energy metabolism and attenuated neural plasticity. Hence, we propose that serotonin-mediated behavioural inhibition may have evolved in vertebrates to minimize stress exposure in vulnerable individuals.
Department of Biosciences, University of Oslo, PO Box 1041, Blindern, 0316 Oslo, Norway; Uni Research AS, PO Box 7810, 5020 Bergen, Norway.
Marco A
MA
Vindas
Department of Biosciences, University of Oslo, PO Box 1041, Blindern, 0316 Oslo, Norway; Bjørknes College, Oslo, Norway.
Ida B
IB
Johansen
Institute of Marine Research , 5984 Matredal , Norway.
Ole
O
Folkedal
National Institute of Aquatic Resources, Section for Aquaculture , Technical University of Denmark, North Sea Center , PO Box 101, 9850 Hirtshals , Denmark.
Erik
E
Höglund
Department of Organismal Animal Physiology , Radboud University , Institute for Water and Wetland Research, Heyendaalseweg 135, 6525 AJ, Nijmegen , The Netherlands.
Marnix
M
Gorissen
Department of Organismal Animal Physiology , Radboud University , Institute for Water and Wetland Research, Heyendaalseweg 135, 6525 AJ, Nijmegen , The Netherlands.
Gert
G
Flik
Institute of Marine Research , 5984 Matredal , Norway.
Tore S
TS
Kristiansen
Department of Animal and Aquacultural Sciences , Norwegian University of Life Sciences , PO Box 5003, 1432 Ås , Norway.
Øyvind
Ø
Øverli
coping; cortisol; neurochemistry; serotonin; stress